package repo

import (
	"database/sql"
	"embed"
	"log/slog"
	"time"

	"github.com/pressly/goose/v3"
)

//go:embed migrations/*.sql
var migrationFS embed.FS

// runMigrations handles all database migrations using goose.
func runMigrations(db *sql.DB) error {
	needsOldMigrate := hasTable(db, "events_old") || (hasTable(db, "events") && !hasCol(db, "events", "user_id"))
	if needsOldMigrate {
		slog.Info("migrating from old schema to new schema")
		for _, t := range []string{"events", "days_off", "settings"} {
			if hasTable(db, t) {
				if _, err := db.Exec("ALTER TABLE " + t + " RENAME TO " + t + "_old"); err != nil {
					return err
				}
			}
		}
	}

	goose.SetBaseFS(migrationFS)
	if err := goose.SetDialect("sqlite3"); err != nil {
		return err
	}
	if err := goose.Up(db, "migrations"); err != nil {
		return err
	}

	if needsOldMigrate {
		if err := migrateFromOldSchemaData(db); err != nil {
			return err
		}
	}

	return nil
}

func hasTable(db *sql.DB, name string) bool {
	var exists int
	if err := db.QueryRow("SELECT COUNT(1) FROM sqlite_master WHERE type='table' AND name=?", name).Scan(&exists); err != nil {
		return false
	}
	return exists > 0
}

func hasCol(db *sql.DB, table, column string) bool {
	rows, err := db.Query("PRAGMA table_info(" + table + ")")
	if err != nil {
		return false
	}
	defer rows.Close()
	for rows.Next() {
		var cid int
		var name, ctype string
		var notnull, pk int
		var dflt sql.NullString
		if err := rows.Scan(&cid, &name, &ctype, &notnull, &dflt, &pk); err != nil {
			return false
		}
		if name == column {
			return true
		}
	}
	return false
}

func migrateFromOldSchemaData(db *sql.DB) error {
	migrateUsers(db)
	migrateDaysOff(db)
	migrateEvents(db)
	migrateSettings(db)

	for _, t := range []string{"days_off_old", "settings_old", "events_old"} {
		if hasTable(db, t) {
			if _, err := db.Exec("DROP TABLE IF EXISTS " + t); err != nil {
				slog.Warn("failed to drop old table", "table", t, "error", err)
			}
		}
	}

	slog.Info("migration complete")
	return nil
}

func migrateUsers(db *sql.DB) {
	if !hasTable(db, "events_old") {
		return
	}
	rows, err := db.Query("SELECT DISTINCT chat_id FROM events_old")
	if err != nil {
		slog.Warn("migration: failed to query events_old for users", "error", err)
		return
	}
	defer rows.Close()
	for rows.Next() {
		var chatID int64
		if err := rows.Scan(&chatID); err != nil {
			slog.Warn("migration: scan failed", "error", err)
			continue
		}
		if _, err := db.Exec(
			"INSERT OR IGNORE INTO users (chat_id, timezone) VALUES (?, 'Asia/Tehran')",
			chatID,
		); err != nil {
			slog.Warn("migration: failed to insert user", "chat_id", chatID, "error", err)
		}
	}
}

func migrateDaysOff(db *sql.DB) {
	if !hasTable(db, "days_off_old") {
		return
	}
	rows, err := db.Query("SELECT chat_id, date, reason FROM days_off_old")
	if err != nil {
		slog.Warn("migration: failed to query days_off_old", "error", err)
		return
	}
	defer rows.Close()
	for rows.Next() {
		var chatID int64
		var date, reason string
		if err := rows.Scan(&chatID, &date, &reason); err != nil {
			slog.Warn("migration: scan failed", "error", err)
			continue
		}
		var userID int64
		if err := db.QueryRow("SELECT id FROM users WHERE chat_id=?", chatID).Scan(&userID); err != nil {
			slog.Warn("migration: user not found", "chat_id", chatID, "error", err)
			continue
		}
		if _, err := db.Exec(
			"INSERT INTO days (user_id, date, is_day_off, day_off_reason) VALUES (?, ?, 1, ?) ON CONFLICT(user_id, date) DO UPDATE SET is_day_off=1, day_off_reason=excluded.day_off_reason",
			userID, date, reason,
		); err != nil {
			slog.Warn("migration: failed to insert day_off", "user_id", userID, "date", date, "error", err)
		}
	}
}

func migrateEvents(db *sql.DB) {
	if !hasTable(db, "events_old") {
		return
	}
	rows, err := db.Query("SELECT chat_id, event_type, occurred_at, note, created_at FROM events_old ORDER BY occurred_at ASC")
	if err != nil {
		slog.Warn("migration: failed to query events_old", "error", err)
		return
	}
	defer rows.Close()
	for rows.Next() {
		var chatID int64
		var eventType, note string
		var occurredAt, createdAt int64
		if err := rows.Scan(&chatID, &eventType, &occurredAt, &note, &createdAt); err != nil {
			slog.Warn("migration: scan failed", "error", err)
			continue
		}
		var userID int64
		if err := db.QueryRow("SELECT id FROM users WHERE chat_id=?", chatID).Scan(&userID); err != nil {
			slog.Warn("migration: user not found", "chat_id", chatID, "error", err)
			continue
		}
		date := time.Unix(occurredAt, 0).UTC().Format("2006-01-02")
		if _, err := db.Exec("INSERT OR IGNORE INTO days (user_id, date) VALUES (?, ?)", userID, date); err != nil {
			slog.Warn("migration: failed to insert day", "user_id", userID, "date", date, "error", err)
			continue
		}
		var dayID int64
		if err := db.QueryRow("SELECT id FROM days WHERE user_id=? AND date=?", userID, date).Scan(&dayID); err != nil {
			slog.Warn("migration: day not found", "user_id", userID, "date", date, "error", err)
			continue
		}
		if _, err := db.Exec(
			"INSERT INTO events (user_id, day_id, event_type, occurred_at, note, created_at) VALUES (?, ?, ?, ?, ?, ?)",
			userID, dayID, eventType, occurredAt, note, createdAt,
		); err != nil {
			slog.Warn("migration: failed to insert event", "user_id", userID, "error", err)
		}
	}
}

func migrateSettings(db *sql.DB) {
	if !hasTable(db, "settings_old") {
		return
	}
	rows, err := db.Query("SELECT chat_id, key, value FROM settings_old")
	if err != nil {
		slog.Warn("migration: failed to query settings_old", "error", err)
		return
	}
	defer rows.Close()
	for rows.Next() {
		var chatID int64
		var key, value string
		if err := rows.Scan(&chatID, &key, &value); err != nil {
			slog.Warn("migration: scan failed", "error", err)
			continue
		}
		if key == "remote_flag" {
			var userID int64
			if err := db.QueryRow("SELECT id FROM users WHERE chat_id=?", chatID).Scan(&userID); err != nil {
				slog.Warn("migration: user not found", "chat_id", chatID, "error", err)
				continue
			}
			wt := int64(1)
			if value == "remote" {
				wt = 2
			}
			db.Exec("UPDATE days SET current_work_type_id=? WHERE user_id=? AND date=?", wt, userID, time.Now().UTC().Format("2006-01-02"))
		}
	}
}