package engine

import (
	"database/sql"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"log"
	"slices"
	"strconv"
	"strings"

	_ "github.com/mattn/go-sqlite3"

	engine "git.pablu.de/pablu/sqv-engine/sql"
)

type Manager struct {
	parser *engine.Parser

	conn   *sql.DB
	tables []Table
}

func NewManagerFromFile(sqlTxt string) *Manager {
	return &Manager{
		parser: engine.NewParser(strings.NewReader(sqlTxt)),
	}
}

func NewManager(path string) (*Manager, error) {
	db, err := sql.Open("sqlite3", path)
	if err != nil {
		return nil, err
	}

	var sqls []string
	r, err := db.Query("SELECT name, sql FROM sqlite_schema WHERE type = 'table' AND name NOT LIKE 'sqlite_%'")
	if err != nil {
		return nil, err
	}

	for r.Next() {
		var name, sql string

		if err := r.Scan(&name, &sql); err != nil {
			return nil, err
		}

		sqls = append(sqls, sql)
	}

	schema := strings.Join(sqls, ";")
	schema += ";"
	// fmt.Println(schema)

	return &Manager{
		parser: engine.NewParser(strings.NewReader(schema)),
		conn:   db,
	}, nil
}

func (m *Manager) RunSql(sqlText string) (Table, error) {
	p := engine.NewParser(strings.NewReader(sqlText))
	stmt, err := p.Parse()
	if err != nil && !errors.Is(err, io.EOF) {
		return Table{}, err
	}

	selectStmt, ok := stmt.(*engine.SelectStatement)
	if !ok {
		panic("HELP ITS NOT A SELECT STATMET")
	}

	table, ok := m.GetTable(selectStmt.From)
	if !ok {
		panic("HELP TABLE NOT FOUND")
	}

	rows, err := m.conn.Query(sqlText)
	if err != nil {
		return Table{}, err
	}
	table.Rows = make([]Row, 0)

	if slices.Contains(selectStmt.Fields, "*") {
		for rows.Next() {
			cols := make([]any, len(table.Columns))

			for i, column := range table.Columns {
				switch column.Type {
				case BLOB:
					cols[i] = new([]byte)
				case TEXT:
					cols[i] = new(string)
				case INTEGER:
					cols[i] = new(int)
				case REAL:
					cols[i] = new(float64)
				default:
					panic("THIS SHOULD NEVER HAPPEN, WE HIT AN UNKNOWN COLUMN.TYPE")
				}
			}

			err = rows.Scan(cols...)
			if err != nil {
				return Table{}, err
			}

			table.Rows = append(table.Rows, Row{
				Values: anyToStr(cols),
			})
		}

		return table, nil
	} else {
		columns := make([]Column, len(selectStmt.Fields))
		firstTime := true

		for rows.Next() {

			cols := make([]any, len(selectStmt.Fields))

			for i, s := range selectStmt.Fields {
				for _, column := range table.Columns {
					if column.Name != s {
						continue
					}

					if firstTime {
						columns[i] = column
					}

					switch column.Type {
					case BLOB:
						cols[i] = new([]byte)
					case TEXT:
						cols[i] = new(string)
					case INTEGER:
						cols[i] = new(int)
					case REAL:
						cols[i] = new(float64)
					default:
						panic("THIS SHOULD NEVER HAPPEN, WE HIT AN UNKNOWN COLUMN.TYPE")
					}
				}
			}

			firstTime = false

			err = rows.Scan(cols...)
			if err != nil {
				return Table{}, err
			}

			table.Rows = append(table.Rows, Row{
				Values: anyToStr(cols),
			})
		}

		nTable := Table{
			Name:    selectStmt.From,
			Columns: columns,
			Rows:    table.Rows,
		}

		return nTable, nil
	}
}

func (m *Manager) Start() error {
	for {
		stmt, err := m.parser.Parse()
		if err != nil && errors.Is(err, io.EOF) {
			fmt.Println("Finished parsing")
			break
		} else if err != nil {
			return err
		}

		switch v := stmt.(type) {
		case *engine.CreateTableStatement:
			t, err := m.convertCreateTableStatementToTable(v)
			if err != nil {
				return err
			}
			m.tables = append(m.tables, t)

		default:
			panic("NOT IMPLEMENTED")
		}
	}

	return nil
}

func (m *Manager) Refresh(sqlTxt string) error {
	m.parser = engine.NewParser(strings.NewReader(sqlTxt))
	m.tables = make([]Table, 0)

	return m.Start()
}

func (m *Manager) GetTables() []Table {
	return m.tables
}

func (m *Manager) GetTable(name string) (Table, bool) {
	index := slices.IndexFunc(m.tables, func(t Table) bool {
		return t.Name == name
	})

	if index < 0 {
		return Table{}, false
	}
	table := m.tables[index]

	return table, true
}

func (m *Manager) LoadTable(table *Table) error {
	rows, err := m.conn.Query(fmt.Sprintf("SELECT * FROM %v", table.Name))
	if err != nil {
		return err
	}
	table.Rows = make([]Row, 0)

	for rows.Next() {
		cols := make([]any, len(table.Columns))
		for i, column := range table.Columns {
			switch column.Type {
			case BLOB:
				cols[i] = new([]byte)
			case TEXT:
				cols[i] = new(string)
			case INTEGER:
				cols[i] = new(int)
			case REAL:
				cols[i] = new(float64)
			default:
				panic("THIS SHOULD NEVER HAPPEN, WE HIT AN UNKNOWN COLUMN.TYPE")
			}
		}

		err = rows.Scan(cols...)
		if err != nil {
			return err
		}

		table.Rows = append(table.Rows, Row{
			Values: anyToStr(cols),
		})
	}

	return nil
}

func anyToStr(a []any) []string {
	res := make([]string, len(a))

	for i, c := range a {
		switch v := c.(type) {
		case *string:
			res[i] = *v
		case *int:
			res[i] = strconv.Itoa(*v)
		case *float64:
			res[i] = strconv.FormatFloat(*v, 'f', 2, 64)
		case *[]byte:
			res[i] = hex.EncodeToString(*v)
		default:
			panic("THIS SHOULD NEVER HAPPEN, WE GOT SERVED AN UNKNOWN TYPE")
		}
	}

	return res
}

func (m *Manager) convertCreateTableStatementToTable(cts *engine.CreateTableStatement) (Table, error) {
	res := Table{
		Name:    cts.TableName,
		Columns: make([]Column, len(cts.Columns)),
		Rows:    make([]Row, 0),
	}

	for i, column := range cts.Columns {
		flags := extrasToFlags(column.Extra)
		var ref *Column = nil
		if flags.Has(FOREIGN_KEY) {
			index := slices.IndexFunc(column.Extra, func(c string) bool {
				return strings.HasPrefix(c, "ref")
			})
			refExtra := column.Extra[index]
			refStr := strings.Split(refExtra, " ")[1]

			s := strings.Split(refStr, ".")
			tableName := s[0]
			columnName := s[1]

			refTable, ok := m.GetTable(tableName)
			if !ok {
				fmt.Println(m.tables)
				return Table{}, fmt.Errorf("Reference table '%v' not found", tableName)
			}

			colIndex := slices.IndexFunc(refTable.Columns, func(c Column) bool {
				return c.Name == columnName
			})

			ref = &refTable.Columns[colIndex]
		}

		var columnType ColumnType
		switch column.Type {
		case "REAL":
			columnType = REAL
		case "BLOB":
			columnType = BLOB
		case "TEXT":
			columnType = TEXT
		case "INTEGER":
			columnType = INTEGER
		default:
			panic("This shouldnt happen")
		}

		res.Columns[i] = Column{
			Type:      columnType,
			Name:      column.Name,
			Reference: ref,
			Flags:     flags,
		}
	}

	return res, nil
}

func extrasToFlags(extras []string) ColumnFlag {
	res := NONE
	for _, extra := range extras {

		// This is not good
		switch strings.Split(extra, " ")[0] {
		case "PRIMARY_KEY":
			res |= PRIMARY_KEY
		case "ref":
			res |= FOREIGN_KEY
		case "NOT_NULL":
			res |= NOT_NULL
		default:
			log.Panicf("NOT IMPLEMENTED EXTRA: %v", extra)
		}
	}

	return res
}