package database

import (
	"context"
	"embed"
	"fmt"
	"io/fs"
	"sort"
	"strconv"
	"strings"

	"github.com/atlasos/calypso/internal/common/logger"
)

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

// RunMigrations executes all pending database migrations
func RunMigrations(ctx context.Context, db *DB) error {
	log := logger.NewLogger("migrations")

	// Create migrations table if it doesn't exist
	if err := createMigrationsTable(ctx, db); err != nil {
		return fmt.Errorf("failed to create migrations table: %w", err)
	}

	// Get all migration files
	migrations, err := getMigrationFiles()
	if err != nil {
		return fmt.Errorf("failed to read migration files: %w", err)
	}

	// Get applied migrations
	applied, err := getAppliedMigrations(ctx, db)
	if err != nil {
		return fmt.Errorf("failed to get applied migrations: %w", err)
	}

	// Apply pending migrations
	for _, migration := range migrations {
		if applied[migration.Version] {
			log.Debug("Migration already applied", "version", migration.Version)
			continue
		}

		log.Info("Applying migration", "version", migration.Version, "name", migration.Name)

		// Read migration SQL
		sql, err := migrationsFS.ReadFile(fmt.Sprintf("migrations/%s", migration.Filename))
		if err != nil {
			return fmt.Errorf("failed to read migration file %s: %w", migration.Filename, err)
		}

		// Execute migration in a transaction
		tx, err := db.BeginTx(ctx, nil)
		if err != nil {
			return fmt.Errorf("failed to begin transaction: %w", err)
		}

		if _, err := tx.ExecContext(ctx, string(sql)); err != nil {
			tx.Rollback()
			return fmt.Errorf("failed to execute migration %d: %w", migration.Version, err)
		}

		// Record migration
		if _, err := tx.ExecContext(ctx,
			"INSERT INTO schema_migrations (version, applied_at) VALUES ($1, NOW())",
			migration.Version,
		); err != nil {
			tx.Rollback()
			return fmt.Errorf("failed to record migration %d: %w", migration.Version, err)
		}

		if err := tx.Commit(); err != nil {
			return fmt.Errorf("failed to commit migration %d: %w", migration.Version, err)
		}

		log.Info("Migration applied successfully", "version", migration.Version)
	}

	return nil
}

// Migration represents a database migration
type Migration struct {
	Version  int
	Name     string
	Filename string
}

// getMigrationFiles returns all migration files sorted by version
func getMigrationFiles() ([]Migration, error) {
	entries, err := fs.ReadDir(migrationsFS, "migrations")
	if err != nil {
		return nil, err
	}

	var migrations []Migration
	for _, entry := range entries {
		if entry.IsDir() {
			continue
		}

		filename := entry.Name()
		if !strings.HasSuffix(filename, ".sql") {
			continue
		}

		// Parse version from filename: 001_initial_schema.sql
		parts := strings.SplitN(filename, "_", 2)
		if len(parts) < 2 {
			continue
		}

		version, err := strconv.Atoi(parts[0])
		if err != nil {
			continue
		}

		name := strings.TrimSuffix(parts[1], ".sql")
		migrations = append(migrations, Migration{
			Version:  version,
			Name:     name,
			Filename: filename,
		})
	}

	// Sort by version
	sort.Slice(migrations, func(i, j int) bool {
		return migrations[i].Version < migrations[j].Version
	})

	return migrations, nil
}

// createMigrationsTable creates the schema_migrations table
func createMigrationsTable(ctx context.Context, db *DB) error {
	query := `
		CREATE TABLE IF NOT EXISTS schema_migrations (
			version INTEGER PRIMARY KEY,
			applied_at TIMESTAMP NOT NULL DEFAULT NOW()
		)
	`
	_, err := db.ExecContext(ctx, query)
	return err
}

// getAppliedMigrations returns a map of applied migration versions
func getAppliedMigrations(ctx context.Context, db *DB) (map[int]bool, error) {
	rows, err := db.QueryContext(ctx, "SELECT version FROM schema_migrations ORDER BY version")
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	applied := make(map[int]bool)
	for rows.Next() {
		var version int
		if err := rows.Scan(&version); err != nil {
			return nil, err
		}
		applied[version] = true
	}

	return applied, rows.Err()
}