package main

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"path"
	"sort"
	"strings"
	"sync"
	"time"
)

type GitHubService interface {
	ListPullRequests(context.Context, string, string, int, bool) ([]PullRequest, error)
	GetPullRequest(context.Context, string, string, int) (PRDetails, error)
}

type GitHubWriteService interface {
	SetThreadResolved(context.Context, string, bool) (ReviewThread, error)
	ReplyToThread(context.Context, string, string) (ReviewComment, error)
}

type GitHubPullRequestWriteService interface {
	UpdatePullRequest(context.Context, string, PullRequestMetadata) (PullRequestMetadata, error)
}

type GitHubBranchService interface {
	ListBranches(context.Context, string, string) ([]RepositoryBranch, error)
}

type GitHubClient struct {
	endpoint      string
	token         string
	http          *http.Client
	conflicts     conflictFileLoader
	conflictMu    sync.Mutex
	conflictCache map[string]conflictFileResult
}

func NewGitHubClient(endpoint, token string) *GitHubClient {
	return &GitHubClient{
		endpoint:      endpoint,
		token:         token,
		http:          &http.Client{Timeout: 20 * time.Second},
		conflicts:     analyzeConflictFiles,
		conflictCache: make(map[string]conflictFileResult),
	}
}

type graphQLRequest struct {
	Query     string         `json:"query"`
	Variables map[string]any `json:"variables"`
}

type graphQLError struct {
	Message string `json:"message"`
}

type graphQLResponse[T any] struct {
	Data   T              `json:"data"`
	Errors []graphQLError `json:"errors"`
}

func (c *GitHubClient) query(ctx context.Context, query string, variables map[string]any, target any) error {
	payload, err := json.Marshal(graphQLRequest{Query: query, Variables: variables})
	if err != nil {
		return fmt.Errorf("encode GraphQL request: %w", err)
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.endpoint, bytes.NewReader(payload))
	if err != nil {
		return fmt.Errorf("create GraphQL request: %w", err)
	}
	req.Header.Set("Authorization", "Bearer "+c.token)
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("User-Agent", "gh-threads")

	resp, err := c.http.Do(req)
	if err != nil {
		return fmt.Errorf("GitHub request: %w", err)
	}
	defer resp.Body.Close()
	body, err := io.ReadAll(io.LimitReader(resp.Body, 32<<20))
	if err != nil {
		return fmt.Errorf("read GitHub response: %w", err)
	}
	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("GitHub returned %s: %s", resp.Status, strings.TrimSpace(string(body)))
	}

	envelope := graphQLResponse[json.RawMessage]{}
	if err := json.Unmarshal(body, &envelope); err != nil {
		return fmt.Errorf("decode GitHub response: %w", err)
	}
	if len(envelope.Errors) > 0 {
		messages := make([]string, len(envelope.Errors))
		for i, item := range envelope.Errors {
			messages[i] = item.Message
		}
		return errors.New(strings.Join(messages, "; "))
	}
	if err := json.Unmarshal(envelope.Data, target); err != nil {
		return fmt.Errorf("decode GitHub data: %w", err)
	}
	return nil
}

const listPRsQuery = `
query PullRequests($query: String!, $first: Int!, $after: String) {
  viewer { login }
  search(query: $query, type: ISSUE, first: $first, after: $after) {
    pageInfo { hasNextPage endCursor }
    nodes {
      ... on PullRequest {
        id number title url isDraft updatedAt
        author { login }
        repository {
          name
          nameWithOwner
          owner { login }
        }
        reviewThreads(first: 1) { totalCount }
      }
    }
  }
}`

const repositoryBranchesQuery = `
query RepositoryBranches($owner: String!, $name: String!, $after: String) {
  repository(owner: $owner, name: $name) {
    defaultBranchRef { name }
    refs(refPrefix: "refs/heads/", first: 100, after: $after) {
      pageInfo { hasNextPage endCursor }
      nodes {
        name
        target {
          ... on Commit { committedDate }
        }
      }
    }
  }
}`

func (c *GitHubClient) ListBranches(
	ctx context.Context, owner, name string,
) ([]RepositoryBranch, error) {
	var branches []RepositoryBranch
	after := ""
	defaultBranch := ""
	for {
		var data struct {
			Repository *struct {
				DefaultBranchRef *struct{ Name string }
				Refs             struct {
					PageInfo githubPageInfo
					Nodes    []struct {
						Name   string
						Target *struct{ CommittedDate time.Time }
					}
				}
			}
		}
		if err := c.query(ctx, repositoryBranchesQuery, map[string]any{
			"owner": owner,
			"name":  name,
			"after": nullableCursor(after),
		}, &data); err != nil {
			return nil, err
		}
		if data.Repository == nil {
			return nil, fmt.Errorf("repository %s/%s was not found", owner, name)
		}
		if data.Repository.DefaultBranchRef != nil {
			defaultBranch = data.Repository.DefaultBranchRef.Name
		}
		for _, node := range data.Repository.Refs.Nodes {
			if node.Name == "" {
				continue
			}
			branch := RepositoryBranch{Name: node.Name, IsDefault: node.Name == defaultBranch}
			if node.Target != nil {
				branch.UpdatedAt = node.Target.CommittedDate
			}
			branches = append(branches, branch)
		}
		if !data.Repository.Refs.PageInfo.HasNextPage {
			break
		}
		after = data.Repository.Refs.PageInfo.EndCursor
		if after == "" {
			return nil, errors.New("GitHub returned an empty branch pagination cursor")
		}
	}
	sort.SliceStable(branches, func(i, j int) bool {
		if branches[i].IsDefault != branches[j].IsDefault {
			return branches[i].IsDefault
		}
		if !branches[i].UpdatedAt.Equal(branches[j].UpdatedAt) {
			return branches[i].UpdatedAt.After(branches[j].UpdatedAt)
		}
		return strings.ToLower(branches[i].Name) < strings.ToLower(branches[j].Name)
	})
	return branches, nil
}

type githubPRSearchNode struct {
	ID         string       `json:"id"`
	Number     int          `json:"number"`
	Title      string       `json:"title"`
	URL        string       `json:"url"`
	IsDraft    bool         `json:"isDraft"`
	UpdatedAt  time.Time    `json:"updatedAt"`
	Author     *githubActor `json:"author"`
	Repository struct {
		Name, NameWithOwner string
		Owner               githubActor
	}
	ReviewThreads struct{ TotalCount int }
}

const reviewThreadsPageQuery = `
query ReviewThreadsPage($owner: String!, $name: String!, $number: Int!, $after: String) {
  repository(owner: $owner, name: $name) {
    pullRequest(number: $number) {
      reviewThreads(first: 100, after: $after) {
        pageInfo { hasNextPage endCursor }
        nodes {
          id isResolved isOutdated viewerCanResolve viewerCanUnresolve viewerCanReply path
          line originalLine diffSide
          startLine originalStartLine startDiffSide
          comments(first: 100) {
            pageInfo { hasNextPage endCursor }
            nodes {
              id body diffHunk createdAt url outdated
              line startLine originalLine originalStartLine
              originalCommit { oid }
              author { login }
              reactionGroups {
                content viewerHasReacted
                reactors { totalCount }
              }
            }
          }
        }
      }
    }
  }
}`

const reviewCommentsPageQuery = `
query ReviewCommentsPage($id: ID!, $after: String) {
  node(id: $id) {
    ... on PullRequestReviewThread {
      comments(first: 100, after: $after) {
        pageInfo { hasNextPage endCursor }
        nodes {
          id body diffHunk createdAt url outdated
          line startLine originalLine originalStartLine
          originalCommit { oid }
          author { login }
          reactionGroups {
            content viewerHasReacted
            reactors { totalCount }
          }
        }
      }
    }
  }
}`

const conversationPageQuery = `
query ConversationPage($owner: String!, $name: String!, $number: Int!, $after: String) {
  repository(owner: $owner, name: $name) {
    pullRequest(number: $number) {
      comments(first: 100, after: $after) {
        totalCount
        pageInfo { hasNextPage endCursor }
        nodes { id body url createdAt author { login } }
      }
    }
  }
}`

const reviewsPageQuery = `
query ReviewsPage($owner: String!, $name: String!, $number: Int!, $after: String) {
  repository(owner: $owner, name: $name) {
    pullRequest(number: $number) {
      reviews(first: 100, after: $after) {
        pageInfo { hasNextPage endCursor }
        nodes { id body state url submittedAt author { login } commit { oid } }
      }
    }
  }
}`

func (c *GitHubClient) ListPullRequests(ctx context.Context, owner, name string, limit int, showAll bool) ([]PullRequest, error) {
	if showAll && owner == "" {
		return nil, errors.New("--all requires --repo to avoid an unbounded global search")
	}
	search := "is:pr is:open sort:updated-desc"
	if owner != "" {
		search += " repo:" + owner + "/" + name
	}
	if !showAll {
		search += " assignee:@me"
	}
	var nodes []githubPRSearchNode
	viewer := ""
	after := ""
	loaded := 0
	for loaded < limit {
		var data struct {
			Viewer githubActor
			Search struct {
				PageInfo githubPageInfo
				Nodes    []githubPRSearchNode
			}
		}
		first := min(100, limit-loaded)
		if err := c.query(ctx, listPRsQuery, map[string]any{
			"query": search, "first": first, "after": nullableCursor(after),
		}, &data); err != nil {
			return nil, err
		}
		viewer = data.Viewer.Login
		nodes = append(nodes, data.Search.Nodes...)
		loaded += first
		if !data.Search.PageInfo.HasNextPage || data.Search.PageInfo.EndCursor == "" {
			break
		}
		after = data.Search.PageInfo.EndCursor
	}
	prs := make([]PullRequest, 0, len(nodes))
	for _, node := range nodes {
		if node.Repository.NameWithOwner == "" {
			continue
		}
		author := "[ghost]"
		if node.Author != nil {
			author = node.Author.Login
		}
		prs = append(prs, PullRequest{
			ID: node.ID, Owner: node.Repository.Owner.Login, Repository: node.Repository.Name,
			RepoWithOwner: node.Repository.NameWithOwner,
			Number:        node.Number, Title: node.Title, URL: node.URL,
			Author: author, IsDraft: node.IsDraft, UpdatedAt: node.UpdatedAt,
			ReviewCount: node.ReviewThreads.TotalCount, ViewerAuthored: author == viewer,
		})
	}
	sort.SliceStable(prs, func(i, j int) bool {
		left, right := strings.ToLower(prs[i].RepoWithOwner), strings.ToLower(prs[j].RepoWithOwner)
		if left != right {
			return left < right
		}
		return prs[i].UpdatedAt.After(prs[j].UpdatedAt)
	})
	return prs, nil
}

func nullableCursor(cursor string) any {
	if cursor == "" {
		return nil
	}
	return cursor
}

const detailsQuery = `
query PullRequestDetails($owner: String!, $name: String!, $number: Int!) {
  repository(owner: $owner, name: $name) {
    url
    viewerPermission
    defaultBranchRef { name }
    rulesets(first: 100, includeParents: true, targets: [BRANCH]) {
      nodes {
        name enforcement target
        conditions { refName { include exclude } }
        rules(first: 100) { nodes { type } }
      }
    }
    pullRequest(number: $number) {
      id number title url body isDraft createdAt updatedAt
      mergeable mergeStateStatus reviewDecision
      mergeQueueEntry { state position enqueuedAt estimatedTimeToMerge }
      baseRefName headRefName headRefOid
      viewerCanUpdate viewerCanReact viewerCanSubscribe viewerCanEnableAutoMerge
      baseRef {
        target { ... on Commit { oid } }
        branchProtectionRule {
          requiresApprovingReviews requiredApprovingReviewCount
          requiresStatusChecks requiresConversationResolution
          requiresCodeOwnerReviews
          requiresDeployments requiredDeploymentEnvironments
          requiresStrictStatusChecks requiresLinearHistory requiresCommitSignatures
        }
      }
      author { login }
      assignees(first: 20) { nodes { login } }
      labels(first: 20) { nodes { name } }
      milestone { title }
      additions deletions changedFiles
      comments(first: 100) {
        totalCount
        pageInfo { hasNextPage endCursor }
        nodes { id body url createdAt author { login } }
      }
      reviews(first: 100) {
        pageInfo { hasNextPage endCursor }
        nodes { id body state url submittedAt author { login } commit { oid } }
      }
      reviewRequests(first: 50) {
        nodes {
          requestedReviewer {
            ... on User { login }
            ... on Team { name }
          }
        }
      }
      latestReviews(first: 50) { nodes { state author { login } } }
      commits(last: 1) {
        totalCount
        nodes {
          commit {
            oid
            statusCheckRollup {
              id
              state
              contexts(first: 100) {
                pageInfo { hasNextPage endCursor }
                nodes {
                  ... on CheckRun {
                    id name status conclusion detailsUrl
                    title summary text
                  }
                  ... on StatusContext { context state targetUrl }
                }
              }
            }
          }
        }
      }
      timelineItems(first: 100, itemTypes: [PULL_REQUEST_COMMIT, HEAD_REF_FORCE_PUSHED_EVENT]) {
        pageInfo { hasNextPage endCursor }
        nodes {
          ... on PullRequestCommit {
            commit { oid committedDate messageHeadline author { user { login } name } }
          }
          ... on HeadRefForcePushedEvent {
            id createdAt actor { login }
            beforeCommit { oid }
            afterCommit { oid }
          }
        }
      }
      reviewThreads(first: 100) {
        pageInfo { hasNextPage endCursor }
        nodes {
          id isResolved isOutdated viewerCanResolve viewerCanUnresolve viewerCanReply path
          line originalLine diffSide
          startLine originalStartLine startDiffSide
          comments(first: 100) {
            pageInfo { hasNextPage endCursor }
            nodes {
              id body diffHunk createdAt url outdated
              line startLine originalLine originalStartLine
              originalCommit { oid }
              author { login }
              reactionGroups {
                content viewerHasReacted
                reactors { totalCount }
              }
            }
          }
        }
      }
    }
  }
}`

const timelinePageQuery = `
query TimelinePage($owner: String!, $name: String!, $number: Int!, $after: String) {
  repository(owner: $owner, name: $name) {
    pullRequest(number: $number) {
      timelineItems(first: 100, after: $after, itemTypes: [PULL_REQUEST_COMMIT, HEAD_REF_FORCE_PUSHED_EVENT]) {
        pageInfo { hasNextPage endCursor }
        nodes {
          ... on PullRequestCommit {
            commit { oid committedDate messageHeadline author { user { login } name } }
          }
          ... on HeadRefForcePushedEvent {
            id createdAt actor { login } beforeCommit { oid } afterCommit { oid }
          }
        }
      }
    }
  }
}`

const checkContextsPageQuery = `
query CheckContextsPage($id: ID!, $after: String) {
  node(id: $id) {
    ... on StatusCheckRollup {
      contexts(first: 100, after: $after) {
        pageInfo { hasNextPage endCursor }
        nodes {
          ... on CheckRun {
            id name status conclusion detailsUrl
            title summary text
          }
          ... on StatusContext { context state targetUrl }
        }
      }
    }
  }
}`

const checkAnnotationsPageQuery = `
query CheckAnnotationsPage($id: ID!, $after: String) {
  node(id: $id) {
    ... on CheckRun {
      annotations(first: 100, after: $after) {
        pageInfo { hasNextPage endCursor }
        nodes {
          path annotationLevel message title
          location { start { line column } end { line column } }
        }
      }
    }
  }
}`

const resolveThreadMutation = `
mutation ResolveReviewThread($input: ResolveReviewThreadInput!) {
  resolveReviewThread(input: $input) {
    thread {
      id isResolved isOutdated viewerCanResolve viewerCanUnresolve viewerCanReply path
      line originalLine diffSide startLine originalStartLine startDiffSide
    }
  }
}`

const unresolveThreadMutation = `
mutation UnresolveReviewThread($input: UnresolveReviewThreadInput!) {
  unresolveReviewThread(input: $input) {
    thread {
      id isResolved isOutdated viewerCanResolve viewerCanUnresolve viewerCanReply path
      line originalLine diffSide startLine originalStartLine startDiffSide
    }
  }
}`

const replyToThreadMutation = `
mutation ReplyToReviewThread($input: AddPullRequestReviewThreadReplyInput!) {
  addPullRequestReviewThreadReply(input: $input) {
    comment {
      id body diffHunk createdAt url outdated
      line startLine originalLine originalStartLine
      originalCommit { oid }
      author { login }
    }
  }
}`

const updatePullRequestMutation = `
mutation UpdatePullRequest($input: UpdatePullRequestInput!) {
  updatePullRequest(input: $input) {
    pullRequest {
      id title body baseRefName updatedAt mergeable mergeStateStatus
    }
  }
}`

type githubActor struct {
	Login string `json:"login"`
	Name  string `json:"name"`
}

type githubPageInfo struct {
	HasNextPage bool   `json:"hasNextPage"`
	EndCursor   string `json:"endCursor"`
}

type githubReviewComment struct {
	ID, Body, DiffHunk, URL         string
	Line, StartLine                 *int
	OriginalLine, OriginalStartLine *int
	Outdated                        bool
	OriginalCommit                  *struct{ OID string }
	CreatedAt                       time.Time
	Author                          *githubActor
	ReactionGroups                  []githubReactionGroup
}

type githubReactionGroup struct {
	Content          string
	ViewerHasReacted bool
	Reactors         struct {
		TotalCount int
	}
}

type githubReviewCommentConnection struct {
	PageInfo githubPageInfo        `json:"pageInfo"`
	Nodes    []githubReviewComment `json:"nodes"`
}

type githubReviewThread struct {
	ID, Path                                             string
	DiffSide, StartDiffSide                              string
	Line, OriginalLine, StartLine, OriginalStartLine     *int
	IsResolved, IsOutdated                               bool
	ViewerCanResolve, ViewerCanUnresolve, ViewerCanReply bool
	Comments                                             githubReviewCommentConnection
}

type githubReviewThreadConnection struct {
	PageInfo githubPageInfo       `json:"pageInfo"`
	Nodes    []githubReviewThread `json:"nodes"`
}

type githubPRComment struct {
	ID, Body, URL string
	CreatedAt     time.Time
	Author        *githubActor
}

type githubPRCommentConnection struct {
	TotalCount int               `json:"totalCount"`
	PageInfo   githubPageInfo    `json:"pageInfo"`
	Nodes      []githubPRComment `json:"nodes"`
}

type githubReviewSummary struct {
	ID, Body, State, URL string
	SubmittedAt          time.Time
	Author               *githubActor
	Commit               *struct{ OID string }
}

type githubReviewSummaryConnection struct {
	PageInfo githubPageInfo        `json:"pageInfo"`
	Nodes    []githubReviewSummary `json:"nodes"`
}

type githubCheckContext struct {
	ID                                   string
	Name, Status, Conclusion, DetailsURL string
	Context, State, TargetURL            string
	Title, Summary, Text                 string
	Annotations                          githubCheckAnnotationConnection
}

type githubCheckAnnotation struct {
	Path, AnnotationLevel, Message, Title string
	Location                              struct {
		Start, End struct {
			Line, Column int
		}
	}
}

type githubCheckAnnotationConnection struct {
	PageInfo githubPageInfo
	Nodes    []githubCheckAnnotation
}

type githubCheckContextConnection struct {
	PageInfo githubPageInfo
	Nodes    []githubCheckContext
}

type githubTimelineNode struct {
	ID, CreatedAtRaw          string
	CreatedAt                 time.Time
	Actor                     *githubActor
	BeforeCommit, AfterCommit *struct{ OID string }
	Commit                    *struct {
		OID, MessageHeadline string
		CommittedDate        time.Time
		Author               *struct {
			Name string
			User *githubActor
		}
	}
}

type githubTimelineConnection struct {
	PageInfo githubPageInfo
	Nodes    []githubTimelineNode
}

type githubRuleset struct {
	Name, Enforcement, Target string
	Conditions                struct {
		RefName *struct{ Include, Exclude []string }
	}
	Rules struct{ Nodes []struct{ Type string } }
}

type githubPullRequestDetails struct {
	ID, Title, URL, Body, Mergeable, MergeStateStatus                             string
	ReviewDecision, BaseRefName, HeadRefName, HeadRefOID                          string
	Number, Additions, Deletions, ChangedFiles                                    int
	IsDraft                                                                       bool
	CreatedAt, UpdatedAt                                                          time.Time
	Author                                                                        *githubActor
	ViewerCanUpdate, ViewerCanReact, ViewerCanSubscribe, ViewerCanEnableAutoMerge bool
	BaseRef                                                                       *struct {
		Target               *struct{ OID string }
		BranchProtectionRule *struct {
			RequiresApprovingReviews, RequiresStatusChecks           bool
			RequiresConversationResolution, RequiresCodeOwnerReviews bool
			RequiredApprovingReviewCount                             int
			RequiresDeployments, RequiresStrictStatusChecks          bool
			RequiresLinearHistory, RequiresCommitSignatures          bool
			RequiredDeploymentEnvironments                           []string
		}
	}
	MergeQueueEntry *struct {
		State                          string
		Position, EstimatedTimeToMerge int
		EnqueuedAt                     time.Time
	}
	Assignees struct {
		Nodes []githubActor `json:"nodes"`
	}
	Labels struct {
		Nodes []struct {
			Name string `json:"name"`
		} `json:"nodes"`
	}
	Milestone *struct {
		Title string `json:"title"`
	}
	Comments       githubPRCommentConnection
	Reviews        githubReviewSummaryConnection
	ReviewRequests struct {
		Nodes []struct {
			RequestedReviewer githubActor `json:"requestedReviewer"`
		} `json:"nodes"`
	}
	LatestReviews struct {
		Nodes []struct {
			State  string
			Author *githubActor
		} `json:"nodes"`
	}
	Commits struct {
		TotalCount int `json:"totalCount"`
		Nodes      []struct {
			Commit struct {
				OID               string
				StatusCheckRollup *struct {
					ID       string
					State    string
					Contexts githubCheckContextConnection
				}
			}
		} `json:"nodes"`
	}
	ReviewThreads githubReviewThreadConnection
	TimelineItems githubTimelineConnection
}

func (c *GitHubClient) allReviewThreads(
	ctx context.Context, owner, name string, number int, connection githubReviewThreadConnection,
) ([]githubReviewThread, error) {
	nodes := append([]githubReviewThread(nil), connection.Nodes...)
	for pages := 0; connection.PageInfo.HasNextPage; pages++ {
		if pages >= 100 {
			return nil, errors.New("review thread pagination exceeded 100 pages")
		}
		var data struct {
			Repository *struct {
				PullRequest *struct {
					ReviewThreads githubReviewThreadConnection `json:"reviewThreads"`
				} `json:"pullRequest"`
			} `json:"repository"`
		}
		variables := map[string]any{
			"owner": owner, "name": name, "number": number, "after": connection.PageInfo.EndCursor,
		}
		if err := c.query(ctx, reviewThreadsPageQuery, variables, &data); err != nil {
			return nil, fmt.Errorf("load more review threads: %w", err)
		}
		if data.Repository == nil || data.Repository.PullRequest == nil {
			return nil, errors.New("pull request disappeared while loading review threads")
		}
		connection = data.Repository.PullRequest.ReviewThreads
		nodes = append(nodes, connection.Nodes...)
	}
	for i := range nodes {
		comments, err := c.allReviewComments(ctx, nodes[i].ID, nodes[i].Comments)
		if err != nil {
			return nil, err
		}
		nodes[i].Comments.Nodes = comments
		nodes[i].Comments.PageInfo = githubPageInfo{}
	}
	return nodes, nil
}

func (c *GitHubClient) allReviewComments(
	ctx context.Context, threadID string, connection githubReviewCommentConnection,
) ([]githubReviewComment, error) {
	nodes := append([]githubReviewComment(nil), connection.Nodes...)
	for pages := 0; connection.PageInfo.HasNextPage; pages++ {
		if pages >= 100 {
			return nil, fmt.Errorf("review comments for thread %s exceeded 100 pages", threadID)
		}
		var data struct {
			Node *struct {
				Comments githubReviewCommentConnection `json:"comments"`
			} `json:"node"`
		}
		if err := c.query(ctx, reviewCommentsPageQuery, map[string]any{
			"id": threadID, "after": connection.PageInfo.EndCursor,
		}, &data); err != nil {
			return nil, fmt.Errorf("load more comments for review thread %s: %w", threadID, err)
		}
		if data.Node == nil {
			return nil, fmt.Errorf("review thread %s disappeared while loading comments", threadID)
		}
		connection = data.Node.Comments
		nodes = append(nodes, connection.Nodes...)
	}
	return nodes, nil
}

func (c *GitHubClient) allConversationComments(
	ctx context.Context, owner, name string, number int, connection githubPRCommentConnection,
) ([]githubPRComment, error) {
	nodes := append([]githubPRComment(nil), connection.Nodes...)
	for pages := 0; connection.PageInfo.HasNextPage; pages++ {
		if pages >= 100 {
			return nil, errors.New("PR conversation pagination exceeded 100 pages")
		}
		var data struct {
			Repository *struct {
				PullRequest *struct {
					Comments githubPRCommentConnection `json:"comments"`
				} `json:"pullRequest"`
			} `json:"repository"`
		}
		if err := c.query(ctx, conversationPageQuery, map[string]any{
			"owner": owner, "name": name, "number": number, "after": connection.PageInfo.EndCursor,
		}, &data); err != nil {
			return nil, fmt.Errorf("load more PR conversation comments: %w", err)
		}
		if data.Repository == nil || data.Repository.PullRequest == nil {
			return nil, errors.New("pull request disappeared while loading conversation")
		}
		connection = data.Repository.PullRequest.Comments
		nodes = append(nodes, connection.Nodes...)
	}
	return nodes, nil
}

func (c *GitHubClient) allReviewSummaries(
	ctx context.Context, owner, name string, number int, connection githubReviewSummaryConnection,
) ([]githubReviewSummary, error) {
	nodes := append([]githubReviewSummary(nil), connection.Nodes...)
	for pages := 0; connection.PageInfo.HasNextPage; pages++ {
		if pages >= 100 {
			return nil, errors.New("review summary pagination exceeded 100 pages")
		}
		var data struct {
			Repository *struct {
				PullRequest *struct {
					Reviews githubReviewSummaryConnection `json:"reviews"`
				} `json:"pullRequest"`
			} `json:"repository"`
		}
		if err := c.query(ctx, reviewsPageQuery, map[string]any{
			"owner": owner, "name": name, "number": number, "after": connection.PageInfo.EndCursor,
		}, &data); err != nil {
			return nil, fmt.Errorf("load more submitted reviews: %w", err)
		}
		if data.Repository == nil || data.Repository.PullRequest == nil {
			return nil, errors.New("pull request disappeared while loading reviews")
		}
		connection = data.Repository.PullRequest.Reviews
		nodes = append(nodes, connection.Nodes...)
	}
	return nodes, nil
}

func (c *GitHubClient) allTimelineItems(
	ctx context.Context, owner, name string, number int, connection githubTimelineConnection,
) ([]githubTimelineNode, error) {
	nodes := append([]githubTimelineNode(nil), connection.Nodes...)
	for pages := 0; connection.PageInfo.HasNextPage; pages++ {
		if pages >= 100 {
			return nil, errors.New("PR timeline pagination exceeded 100 pages")
		}
		var data struct {
			Repository *struct {
				PullRequest *struct{ TimelineItems githubTimelineConnection }
			}
		}
		if err := c.query(ctx, timelinePageQuery, map[string]any{
			"owner": owner, "name": name, "number": number, "after": connection.PageInfo.EndCursor,
		}, &data); err != nil {
			return nil, fmt.Errorf("load more PR timeline events: %w", err)
		}
		if data.Repository == nil || data.Repository.PullRequest == nil {
			return nil, errors.New("pull request disappeared while loading timeline")
		}
		connection = data.Repository.PullRequest.TimelineItems
		nodes = append(nodes, connection.Nodes...)
	}
	return nodes, nil
}

func (c *GitHubClient) allCheckContexts(
	ctx context.Context, connection githubCheckContextConnection, rollupID string,
) ([]githubCheckContext, error) {
	nodes := append([]githubCheckContext(nil), connection.Nodes...)
	for pages := 0; connection.PageInfo.HasNextPage; pages++ {
		if pages >= 100 {
			return nil, errors.New("check context pagination exceeded 100 pages")
		}
		var data struct {
			Node *struct{ Contexts githubCheckContextConnection }
		}
		if err := c.query(ctx, checkContextsPageQuery, map[string]any{
			"id": rollupID, "after": connection.PageInfo.EndCursor,
		}, &data); err != nil {
			return nil, fmt.Errorf("load more check contexts: %w", err)
		}
		if data.Node == nil {
			return nil, errors.New("check rollup disappeared while loading contexts")
		}
		connection = data.Node.Contexts
		nodes = append(nodes, connection.Nodes...)
	}
	for index := range nodes {
		if nodes[index].ID == "" || !checkMayHaveUsefulAnnotations(nodes[index]) {
			continue
		}
		annotations, err := c.checkAnnotations(ctx, nodes[index].ID)
		if err != nil {
			return nil, err
		}
		nodes[index].Annotations.Nodes = annotations
	}
	return nodes, nil
}

func checkMayHaveUsefulAnnotations(check githubCheckContext) bool {
	state := strings.ToUpper(firstNonEmpty(check.Conclusion, check.State, check.Status))
	switch state {
	case "FAILURE", "ERROR", "CANCELLED", "TIMED_OUT", "ACTION_REQUIRED", "STALE":
		return true
	default:
		return false
	}
}

func (c *GitHubClient) checkAnnotations(
	ctx context.Context, checkID string,
) ([]githubCheckAnnotation, error) {
	var data struct {
		Node *struct {
			Annotations githubCheckAnnotationConnection
		}
	}
	if err := c.query(ctx, checkAnnotationsPageQuery, map[string]any{
		"id": checkID, "after": nil,
	}, &data); err != nil {
		return nil, fmt.Errorf("load annotations for check %s: %w", checkID, err)
	}
	if data.Node == nil {
		return nil, fmt.Errorf("check %s disappeared while loading annotations", checkID)
	}
	return c.allCheckAnnotations(ctx, checkID, data.Node.Annotations)
}

func (c *GitHubClient) allCheckAnnotations(
	ctx context.Context, checkID string, connection githubCheckAnnotationConnection,
) ([]githubCheckAnnotation, error) {
	nodes := append([]githubCheckAnnotation(nil), connection.Nodes...)
	for pages := 0; connection.PageInfo.HasNextPage; pages++ {
		if pages >= 100 {
			return nil, fmt.Errorf("annotations for check %s exceeded 100 pages", checkID)
		}
		var data struct {
			Node *struct {
				Annotations githubCheckAnnotationConnection
			}
		}
		if err := c.query(ctx, checkAnnotationsPageQuery, map[string]any{
			"id": checkID, "after": connection.PageInfo.EndCursor,
		}, &data); err != nil {
			return nil, fmt.Errorf("load more annotations for check %s: %w", checkID, err)
		}
		if data.Node == nil {
			return nil, fmt.Errorf("check %s disappeared while loading annotations", checkID)
		}
		connection = data.Node.Annotations
		nodes = append(nodes, connection.Nodes...)
	}
	return nodes, nil
}

func (c *GitHubClient) GetPullRequest(ctx context.Context, owner, name string, number int) (PRDetails, error) {
	var data struct {
		Repository *struct {
			URL              string
			ViewerPermission string `json:"viewerPermission"`
			DefaultBranchRef *struct{ Name string }
			Rulesets         struct{ Nodes []githubRuleset }
			PullRequest      *githubPullRequestDetails `json:"pullRequest"`
		} `json:"repository"`
	}
	if err := c.query(ctx, detailsQuery, map[string]any{"owner": owner, "name": name, "number": number}, &data); err != nil {
		return PRDetails{}, err
	}
	if data.Repository == nil || data.Repository.PullRequest == nil {
		return PRDetails{}, fmt.Errorf("pull request #%d was not found", number)
	}
	node := data.Repository.PullRequest
	var (
		threadNodes       []githubReviewThread
		conversationNodes []githubPRComment
		reviewNodes       []githubReviewSummary
		timelineNodes     []githubTimelineNode
		checkNodes        []githubCheckContext
		threadErr         error
		conversationErr   error
		reviewErr         error
		timelineErr       error
		checkErr          error
		conflictFiles     []string
		conflictFileErr   error
		wait              sync.WaitGroup
	)
	wait.Add(4)
	go func() {
		defer wait.Done()
		threadNodes, threadErr = c.allReviewThreads(ctx, owner, name, number, node.ReviewThreads)
	}()
	go func() {
		defer wait.Done()
		conversationNodes, conversationErr = c.allConversationComments(ctx, owner, name, number, node.Comments)
	}()
	go func() {
		defer wait.Done()
		reviewNodes, reviewErr = c.allReviewSummaries(ctx, owner, name, number, node.Reviews)
	}()
	go func() {
		defer wait.Done()
		timelineNodes, timelineErr = c.allTimelineItems(ctx, owner, name, number, node.TimelineItems)
	}()
	if len(node.Commits.Nodes) > 0 && node.Commits.Nodes[0].Commit.StatusCheckRollup != nil {
		wait.Add(1)
		go func() {
			defer wait.Done()
			rollup := node.Commits.Nodes[0].Commit.StatusCheckRollup
			checkNodes, checkErr = c.allCheckContexts(ctx, rollup.Contexts, rollup.ID)
		}()
	}
	if node.Mergeable == "CONFLICTING" && c.conflicts != nil {
		wait.Add(1)
		go func() {
			defer wait.Done()
			baseOID := ""
			if node.BaseRef != nil && node.BaseRef.Target != nil {
				baseOID = node.BaseRef.Target.OID
			}
			conflictFiles, conflictFileErr = c.loadConflictFiles(
				ctx, data.Repository.URL, number, node.BaseRefName, baseOID, node.HeadRefOID,
			)
		}()
	}
	wait.Wait()
	for _, err := range []error{threadErr, conversationErr, reviewErr, timelineErr, checkErr} {
		if err != nil {
			return PRDetails{}, err
		}
	}
	details := PRDetails{
		PullRequest: PullRequest{
			ID: node.ID, Owner: owner, Repository: name, RepoWithOwner: owner + "/" + name,
			Number: node.Number, Title: node.Title, URL: node.URL,
			Author: actorLogin(node.Author), IsDraft: node.IsDraft, UpdatedAt: node.UpdatedAt,
			ReviewCount: len(threadNodes),
		},
		Body: node.Body, CreatedAt: node.CreatedAt, BaseRef: node.BaseRefName, HeadRef: node.HeadRefName,
		HeadOID: node.HeadRefOID, Mergeable: node.Mergeable, MergeState: node.MergeStateStatus,
		ConflictFiles: conflictFiles,
		Additions:     node.Additions, Deletions: node.Deletions, ChangedFiles: node.ChangedFiles,
		CommitCount: node.Commits.TotalCount, CommentCount: node.Comments.TotalCount,
		CheckState: "NONE", ReviewDecision: node.ReviewDecision,
		Permissions: ViewerPermissions{
			Repository:  data.Repository.ViewerPermission,
			CanUpdatePR: node.ViewerCanUpdate, CanReact: node.ViewerCanReact,
			CanSubscribe: node.ViewerCanSubscribe, CanEnableMerge: node.ViewerCanEnableAutoMerge,
		},
	}
	if conflictFileErr != nil {
		details.ConflictFileError = conflictFileErr.Error()
	}
	if node.BaseRef != nil && node.BaseRef.BranchProtectionRule != nil {
		rule := node.BaseRef.BranchProtectionRule
		details.Requirements = MergeRequirements{
			ApprovalsRequired:       rule.RequiredApprovingReviewCount,
			RequiresApprovals:       rule.RequiresApprovingReviews,
			RequiresStatusChecks:    rule.RequiresStatusChecks,
			RequiresConversation:    rule.RequiresConversationResolution,
			RequiresCodeOwnerReview: rule.RequiresCodeOwnerReviews,
			RequiresDeployments:     rule.RequiresDeployments,
			RequiredDeployments:     append([]string(nil), rule.RequiredDeploymentEnvironments...),
			RequiresStrictChecks:    rule.RequiresStrictStatusChecks,
			RequiresLinearHistory:   rule.RequiresLinearHistory,
			RequiresSignatures:      rule.RequiresCommitSignatures,
		}
	}
	if node.MergeQueueEntry != nil {
		details.MergeQueue = &MergeQueue{
			State: node.MergeQueueEntry.State, Position: node.MergeQueueEntry.Position,
			EnqueuedAt:       node.MergeQueueEntry.EnqueuedAt,
			EstimatedSeconds: node.MergeQueueEntry.EstimatedTimeToMerge,
		}
		details.Requirements.RequiresMergeQueue = true
	}
	for _, ruleset := range data.Repository.Rulesets.Nodes {
		rule := Ruleset{Name: ruleset.Name, Enforcement: ruleset.Enforcement}
		for _, item := range ruleset.Rules.Nodes {
			rule.RuleTypes = append(rule.RuleTypes, item.Type)
			if item.Type == "MERGE_QUEUE" {
				details.Requirements.RequiresMergeQueue = true
			}
		}
		rule.Applies = rulesetApplies(ruleset, node.BaseRefName,
			data.Repository.DefaultBranchRef != nil && data.Repository.DefaultBranchRef.Name == node.BaseRefName)
		details.Rulesets = append(details.Rulesets, rule)
	}
	for _, label := range node.Labels.Nodes {
		details.Labels = append(details.Labels, label.Name)
	}
	if node.Milestone != nil {
		details.Milestone = node.Milestone.Title
	}
	for _, assignee := range node.Assignees.Nodes {
		details.Assignees = append(details.Assignees, assignee.Login)
	}
	reviewers := map[string]string{}
	for _, request := range node.ReviewRequests.Nodes {
		login := firstNonEmpty(request.RequestedReviewer.Login, request.RequestedReviewer.Name)
		if login != "" {
			reviewers[login] = "REVIEW_REQUESTED"
		}
	}
	for _, review := range node.LatestReviews.Nodes {
		if review.Author != nil {
			reviewers[review.Author.Login] = review.State
		}
	}
	for login, state := range reviewers {
		details.Reviewers = append(details.Reviewers, Reviewer{Login: login, State: state})
	}
	sort.Slice(details.Reviewers, func(i, j int) bool { return details.Reviewers[i].Login < details.Reviewers[j].Login })
	if len(node.Commits.Nodes) > 0 && node.Commits.Nodes[0].Commit.StatusCheckRollup != nil {
		rollup := node.Commits.Nodes[0].Commit.StatusCheckRollup
		details.CheckState = rollup.State
		for _, check := range checkNodes {
			name := firstNonEmpty(check.Name, check.Context)
			state := firstNonEmpty(check.Conclusion, check.State, check.Status)
			item := Check{
				ID: check.ID, Name: name, State: state, Conclusion: check.Conclusion,
				URL: firstNonEmpty(check.DetailsURL, check.TargetURL),
			}
			item.Summary = firstNonEmpty(check.Summary, check.Text, check.Title)
			for _, annotation := range check.Annotations.Nodes {
				item.Annotations = append(item.Annotations, CheckAnnotation{
					Path: annotation.Path, StartLine: annotation.Location.Start.Line,
					EndLine: annotation.Location.End.Line,
					Level:   annotation.AnnotationLevel, Title: annotation.Title, Message: annotation.Message,
				})
			}
			details.Checks = append(details.Checks, item)
		}
	}
	for _, event := range timelineNodes {
		if event.Commit != nil {
			author := "[ghost]"
			if event.Commit.Author != nil {
				author = event.Commit.Author.Name
				if event.Commit.Author.User != nil {
					author = actorLogin(event.Commit.Author.User)
				}
			}
			details.Timeline = append(details.Timeline, TimelineEvent{
				Kind: "commit", OID: event.Commit.OID, Title: event.Commit.MessageHeadline,
				Author: author, CreatedAt: event.Commit.CommittedDate,
			})
		} else if event.BeforeCommit != nil || event.AfterCommit != nil {
			details.Timeline = append(details.Timeline, TimelineEvent{
				Kind: "force-push", BeforeOID: commitOID(event.BeforeCommit), AfterOID: commitOID(event.AfterCommit),
				Author: actorLogin(event.Actor), CreatedAt: event.CreatedAt,
			})
		}
	}
	for _, comment := range conversationNodes {
		details.Conversation = append(details.Conversation, PRComment{
			ID: comment.ID, Author: actorLogin(comment.Author), Body: comment.Body,
			URL: comment.URL, CreatedAt: comment.CreatedAt,
		})
	}
	for _, review := range reviewNodes {
		details.Reviews = append(details.Reviews, ReviewSummary{
			ID: review.ID, Author: actorLogin(review.Author), Body: review.Body,
			State: review.State, URL: review.URL, SubmittedAt: review.SubmittedAt,
			CommitOID: commitOID(review.Commit),
		})
	}
	for _, thread := range threadNodes {
		item := convertReviewThread(thread)
		details.Permissions.CanResolveAny = details.Permissions.CanResolveAny || item.ViewerCanResolve
		details.Permissions.CanUnresolveAny = details.Permissions.CanUnresolveAny || item.ViewerCanUnresolve
		details.Permissions.CanReplyAny = details.Permissions.CanReplyAny || item.ViewerCanReply
		details.Threads = append(details.Threads, item)
	}
	return details, nil
}

func (c *GitHubClient) SetThreadResolved(
	ctx context.Context, threadID string, resolved bool,
) (ReviewThread, error) {
	query := resolveThreadMutation
	variables := map[string]any{"input": map[string]any{"threadId": threadID}}
	if resolved {
		var data struct {
			ResolveReviewThread *struct {
				Thread *githubReviewThread
			}
		}
		if err := c.query(ctx, query, variables, &data); err != nil {
			return ReviewThread{}, err
		}
		if data.ResolveReviewThread == nil || data.ResolveReviewThread.Thread == nil {
			return ReviewThread{}, errors.New("GitHub returned no resolved review thread")
		}
		return convertReviewThread(*data.ResolveReviewThread.Thread), nil
	}

	var data struct {
		UnresolveReviewThread *struct {
			Thread *githubReviewThread
		}
	}
	if err := c.query(ctx, unresolveThreadMutation, variables, &data); err != nil {
		return ReviewThread{}, err
	}
	if data.UnresolveReviewThread == nil || data.UnresolveReviewThread.Thread == nil {
		return ReviewThread{}, errors.New("GitHub returned no unresolved review thread")
	}
	return convertReviewThread(*data.UnresolveReviewThread.Thread), nil
}

func (c *GitHubClient) ReplyToThread(
	ctx context.Context, threadID, body string,
) (ReviewComment, error) {
	var data struct {
		AddPullRequestReviewThreadReply *struct {
			Comment *githubReviewComment
		}
	}
	if err := c.query(ctx, replyToThreadMutation, map[string]any{
		"input": map[string]any{
			"pullRequestReviewThreadId": threadID,
			"body":                      body,
		},
	}, &data); err != nil {
		return ReviewComment{}, err
	}
	if data.AddPullRequestReviewThreadReply == nil ||
		data.AddPullRequestReviewThreadReply.Comment == nil {
		return ReviewComment{}, errors.New("GitHub returned no review reply")
	}
	return convertReviewComment(*data.AddPullRequestReviewThreadReply.Comment), nil
}

func (c *GitHubClient) UpdatePullRequest(
	ctx context.Context,
	pullRequestID string,
	update PullRequestMetadata,
) (PullRequestMetadata, error) {
	var data struct {
		UpdatePullRequest *struct {
			PullRequest *struct {
				ID, Title, Body, BaseRefName, Mergeable, MergeStateStatus string
				UpdatedAt                                                 time.Time
			}
		}
	}
	if err := c.query(ctx, updatePullRequestMutation, map[string]any{
		"input": map[string]any{
			"pullRequestId": pullRequestID,
			"title":         update.Title,
			"body":          update.Body,
			"baseRefName":   update.BaseRef,
		},
	}, &data); err != nil {
		return PullRequestMetadata{}, err
	}
	if data.UpdatePullRequest == nil || data.UpdatePullRequest.PullRequest == nil {
		return PullRequestMetadata{}, errors.New("GitHub returned no updated pull request")
	}
	node := data.UpdatePullRequest.PullRequest
	return PullRequestMetadata{
		Title: node.Title, Body: node.Body, BaseRef: node.BaseRefName,
		Mergeable: node.Mergeable, MergeState: node.MergeStateStatus,
		UpdatedAt: node.UpdatedAt,
	}, nil
}

func convertReviewThread(thread githubReviewThread) ReviewThread {
	item := ReviewThread{
		ID: thread.ID, Path: thread.Path, DiffSide: thread.DiffSide,
		IsResolved: thread.IsResolved, IsOutdated: thread.IsOutdated,
		ViewerCanResolve: thread.ViewerCanResolve, ViewerCanUnresolve: thread.ViewerCanUnresolve,
		ViewerCanReply: thread.ViewerCanReply,
	}
	if thread.Line != nil {
		item.Line = *thread.Line
	} else if thread.OriginalLine != nil {
		item.Line = *thread.OriginalLine
	}
	if thread.StartLine != nil {
		item.StartLine = *thread.StartLine
	} else if thread.OriginalStartLine != nil {
		item.StartLine = *thread.OriginalStartLine
	}
	if item.DiffSide == "" {
		item.DiffSide = thread.StartDiffSide
	}
	for _, comment := range thread.Comments.Nodes {
		item.Comments = append(item.Comments, convertReviewComment(comment))
	}
	return item
}

func convertReviewComment(comment githubReviewComment) ReviewComment {
	item := ReviewComment{
		ID: comment.ID, Author: actorLogin(comment.Author), Body: comment.Body,
		DiffHunk: comment.DiffHunk, CreatedAt: comment.CreatedAt, URL: comment.URL,
		Line: intValue(comment.Line), StartLine: intValue(comment.StartLine),
		OriginalLine: intValue(comment.OriginalLine), OriginalStartLine: intValue(comment.OriginalStartLine),
		OriginalCommitOID: commitOID(comment.OriginalCommit), Outdated: comment.Outdated,
	}
	for _, group := range comment.ReactionGroups {
		if group.Reactors.TotalCount > 0 {
			item.Reactions = append(item.Reactions, ReactionSummary{
				Content: group.Content, Count: group.Reactors.TotalCount,
				ViewerHasReacted: group.ViewerHasReacted,
			})
		}
	}
	return item
}

func actorLogin(actor *githubActor) string {
	if actor == nil || actor.Login == "" {
		return "[ghost]"
	}
	return actor.Login
}

func intValue(value *int) int {
	if value == nil {
		return 0
	}
	return *value
}

func commitOID(commit *struct{ OID string }) string {
	if commit == nil {
		return ""
	}
	return commit.OID
}

func rulesetApplies(ruleset githubRuleset, base string, isDefault bool) bool {
	if ruleset.Enforcement == "DISABLED" || ruleset.Target != "" && ruleset.Target != "BRANCH" {
		return false
	}
	if ruleset.Conditions.RefName == nil || len(ruleset.Conditions.RefName.Include) == 0 {
		return true
	}
	ref := "refs/heads/" + base
	matches := func(pattern string) bool {
		switch pattern {
		case "~ALL":
			return true
		case "~DEFAULT_BRANCH":
			return isDefault
		}
		ok, _ := path.Match(pattern, ref)
		return ok
	}
	for _, excluded := range ruleset.Conditions.RefName.Exclude {
		if matches(excluded) {
			return false
		}
	}
	for _, included := range ruleset.Conditions.RefName.Include {
		if matches(included) {
			return true
		}
	}
	return false
}