package db

import (
	"context"
	"database/sql"
	"embed"
	"fmt"
	"io/fs"
	"log/slog"
	"sort"
	"strconv"
	"strings"

	"git.eeqj.de/sneak/chat/internal/config"
	"git.eeqj.de/sneak/chat/internal/logger"
	"go.uber.org/fx"

	_ "github.com/joho/godotenv/autoload"
	_ "modernc.org/sqlite"
)

//go:embed schema/*.sql
var SchemaFiles embed.FS

type DatabaseParams struct {
	fx.In
	Logger *logger.Logger
	Config *config.Config
}

type Database struct {
	DB     *sql.DB
	log    *slog.Logger
	params *DatabaseParams
}

func New(lc fx.Lifecycle, params DatabaseParams) (*Database, error) {
	s := new(Database)
	s.params = &params
	s.log = params.Logger.Get()

	s.log.Info("Database instantiated")

	lc.Append(fx.Hook{
		OnStart: func(ctx context.Context) error {
			s.log.Info("Database OnStart Hook")
			return s.connect(ctx)
		},
		OnStop: func(ctx context.Context) error {
			s.log.Info("Database OnStop Hook")
			if s.DB != nil {
				return s.DB.Close()
			}
			return nil
		},
	})
	return s, nil
}

func (s *Database) connect(ctx context.Context) error {
	dbURL := s.params.Config.DBURL
	if dbURL == "" {
		dbURL = "file:./data.db?_journal_mode=WAL"
	}

	s.log.Info("connecting to database", "url", dbURL)

	d, err := sql.Open("sqlite", dbURL)
	if err != nil {
		s.log.Error("failed to open database", "error", err)
		return err
	}

	if err := d.PingContext(ctx); err != nil {
		s.log.Error("failed to ping database", "error", err)
		return err
	}

	s.DB = d
	s.log.Info("database connected")

	return s.runMigrations(ctx)
}

type migration struct {
	version int
	name    string
	sql     string
}

func (s *Database) runMigrations(ctx context.Context) error {
	// Bootstrap: create schema_migrations table directly (migration 001 also does this,
	// but we need it to exist before we can check which migrations have run)
	_, err := s.DB.ExecContext(ctx, `CREATE TABLE IF NOT EXISTS schema_migrations (
		version INTEGER PRIMARY KEY,
		applied_at DATETIME DEFAULT CURRENT_TIMESTAMP
	)`)
	if err != nil {
		return fmt.Errorf("failed to create schema_migrations table: %w", err)
	}

	// Read all migration files
	entries, err := fs.ReadDir(SchemaFiles, "schema")
	if err != nil {
		return fmt.Errorf("failed to read schema dir: %w", err)
	}

	var migrations []migration
	for _, entry := range entries {
		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".sql") {
			continue
		}

		// Parse version from filename (e.g. "001_initial.sql" -> 1)
		parts := strings.SplitN(entry.Name(), "_", 2)
		if len(parts) < 2 {
			continue
		}
		version, err := strconv.Atoi(parts[0])
		if err != nil {
			continue
		}

		content, err := SchemaFiles.ReadFile("schema/" + entry.Name())
		if err != nil {
			return fmt.Errorf("failed to read migration %s: %w", entry.Name(), err)
		}

		migrations = append(migrations, migration{
			version: version,
			name:    entry.Name(),
			sql:     string(content),
		})
	}

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

	for _, m := range migrations {
		var exists int
		err := s.DB.QueryRowContext(ctx, "SELECT COUNT(*) FROM schema_migrations WHERE version = ?", m.version).Scan(&exists)
		if err != nil {
			return fmt.Errorf("failed to check migration %d: %w", m.version, err)
		}
		if exists > 0 {
			continue
		}

		s.log.Info("applying migration", "version", m.version, "name", m.name)
		if _, err := s.DB.ExecContext(ctx, m.sql); err != nil {
			return fmt.Errorf("failed to apply migration %d (%s): %w", m.version, m.name, err)
		}
		if _, err := s.DB.ExecContext(ctx, "INSERT INTO schema_migrations (version) VALUES (?)", m.version); err != nil {
			return fmt.Errorf("failed to record migration %d: %w", m.version, err)
		}
	}

	s.log.Info("database migrations complete")
	return nil
}