package main

import (
	"fmt"
	"sort"
	"strings"
	"time"

	"github.com/charmbracelet/x/ansi"
)

type branchSuggestion struct {
	branch RepositoryBranch
	score  int
}

func rankBranchSuggestions(
	branches []RepositoryBranch,
	query, current string,
	now time.Time,
) []branchSuggestion {
	query = strings.TrimSpace(strings.ToLower(query))
	current = strings.ToLower(current)
	suggestions := make([]branchSuggestion, 0, len(branches))
	for _, branch := range branches {
		name := strings.ToLower(branch.Name)
		matchScore := 0
		if query != "" {
			var matches bool
			matchScore, matches = fuzzyTermScore([]rune(name), []rune(query))
			if !matches {
				continue
			}
			switch {
			case name == query:
				matchScore += 50000
			case strings.HasPrefix(name, query):
				matchScore += 30000
			case branchSegmentHasPrefix(name, query):
				matchScore += 20000
			}
		}

		score := matchScore * 10
		if branch.IsDefault {
			score += 9000
		}
		if name == current {
			score += 7000
		}
		switch name {
		case "main", "master":
			score += 3500
		case "develop", "development", "dev":
			score += 2500
		}
		if strings.HasPrefix(name, "release/") || strings.HasPrefix(name, "release-") {
			score += 1800
		}
		score += branchFreshnessScore(branch.UpdatedAt, now)
		suggestions = append(suggestions, branchSuggestion{branch: branch, score: score})
	}
	sort.SliceStable(suggestions, func(i, j int) bool {
		if suggestions[i].score != suggestions[j].score {
			return suggestions[i].score > suggestions[j].score
		}
		if !suggestions[i].branch.UpdatedAt.Equal(suggestions[j].branch.UpdatedAt) {
			return suggestions[i].branch.UpdatedAt.After(suggestions[j].branch.UpdatedAt)
		}
		return strings.ToLower(suggestions[i].branch.Name) <
			strings.ToLower(suggestions[j].branch.Name)
	})
	return suggestions
}

func branchSegmentHasPrefix(name, query string) bool {
	for _, segment := range strings.FieldsFunc(name, func(value rune) bool {
		return strings.ContainsRune("/._-", value)
	}) {
		if strings.HasPrefix(segment, query) {
			return true
		}
	}
	return false
}

func branchFreshnessScore(updatedAt, now time.Time) int {
	if updatedAt.IsZero() {
		return 0
	}
	age := now.Sub(updatedAt)
	if age < 0 {
		age = 0
	}
	days := int(age / (24 * time.Hour))
	return max(0, 3000-min(days, 3000))
}

func branchAgeLabel(updatedAt, now time.Time) string {
	if updatedAt.IsZero() {
		return "age unknown"
	}
	age := now.Sub(updatedAt)
	if age < time.Hour {
		return "updated recently"
	}
	if age < 24*time.Hour {
		return fmt.Sprintf("updated %dh ago", int(age/time.Hour))
	}
	days := int(age / (24 * time.Hour))
	if days < 30 {
		return fmt.Sprintf("updated %dd ago", days)
	}
	months := days / 30
	if months < 24 {
		return fmt.Sprintf("updated %dmo ago", months)
	}
	return fmt.Sprintf("updated %dy ago", days/365)
}

func (m App) branchSuggestions() []branchSuggestion {
	suggestions := rankBranchSuggestions(
		m.prEditBranches,
		m.prEditEditors[prEditBaseField].Text,
		m.prEditOriginal.BaseRef,
		time.Now(),
	)
	const maximumVisibleSuggestions = 6
	if len(suggestions) > maximumVisibleSuggestions {
		suggestions = suggestions[:maximumVisibleSuggestions]
	}
	return suggestions
}

func (m *App) moveBranchSuggestion(delta int) {
	suggestions := m.branchSuggestions()
	if len(suggestions) == 0 {
		m.prEditBranchIndex = 0
		return
	}
	m.prEditBranchIndex = (m.prEditBranchIndex + delta + len(suggestions)) % len(suggestions)
}

func (m *App) completeBranchSuggestion() bool {
	suggestions := m.branchSuggestions()
	if len(suggestions) == 0 {
		return false
	}
	index := clamp(m.prEditBranchIndex, 0, len(suggestions)-1)
	name := suggestions[index].branch.Name
	editor := &m.prEditEditors[prEditBaseField]
	if editor.Text == name {
		return false
	}
	editor.Text = name
	editor.Cursor = len([]rune(name))
	m.prEditBranchIndex = 0
	m.err = nil
	return true
}

func (m App) branchCompletionLines(width int) []string {
	width = max(1, width)
	if m.prEditBranchesLoading {
		return []string{dimStyle.Render("  loading repository branches…")}
	}
	if m.prEditBranchesError != "" {
		message := "  branch recommendations unavailable: " + m.prEditBranchesError
		wrapped := ansi.Hardwrap(ansi.Wordwrap(message, width, ""), width, false)
		var lines []string
		for _, line := range strings.Split(wrapped, "\n") {
			lines = append(lines, warnStyle.Render(line))
		}
		return lines
	}
	suggestions := m.branchSuggestions()
	if len(suggestions) == 0 {
		return []string{dimStyle.Render("  no matching repository branches")}
	}
	lines := []string{dimStyle.Render(fmt.Sprintf(
		"  %s choose  •  %s complete  •  %s again advances",
		primaryCombinedKeyLabel(
			m.keybindings.Input.PreviousCompletion,
			m.keybindings.Input.NextCompletion,
		),
		primaryCombinedKeyLabel(m.keybindings.Input.NextField, m.keybindings.Input.Newline),
		primaryKeyLabel(m.keybindings.Input.NextField),
	))}
	now := time.Now()
	for index, suggestion := range suggestions {
		prefix := "    "
		if index == clamp(m.prEditBranchIndex, 0, len(suggestions)-1) {
			prefix = "  ▶ "
		}
		suffix := branchAgeLabel(suggestion.branch.UpdatedAt, now)
		if suggestion.branch.IsDefault {
			suffix = "default • " + suffix
		}
		if suggestion.branch.Name == m.prEditOriginal.BaseRef {
			suffix = "current • " + suffix
		}
		available := max(1, width-len([]rune(prefix))-len([]rune(suffix))-2)
		name := ansi.Truncate(suggestion.branch.Name, available, "…")
		line := prefix + name + strings.Repeat(" ", max(1, available-ansi.StringWidth(name)+1)) + dimStyle.Render(suffix)
		if strings.HasPrefix(prefix, "  ▶") {
			line = titleStyle.Render(prefix+name) +
				strings.Repeat(" ", max(1, available-ansi.StringWidth(name)+1)) +
				dimStyle.Render(suffix)
		}
		lines = append(lines, line)
	}
	return lines
}