package db

import (
	"database/sql"
	"embed"
	"fmt"
	"io/fs"
	"sort"
	"strings"

	_ "modernc.org/sqlite"
)

//go:embed migrations
var migrationsFS embed.FS

func Open(path string) (*sql.DB, error) {
	db, err := sql.Open("sqlite", path)
	if err != nil {
		return nil, err
	}
	// SQLite does not support concurrent writers; a single connection avoids locking errors.
	db.SetMaxOpenConns(1)
	if _, err := db.Exec("PRAGMA journal_mode=WAL; PRAGMA foreign_keys=ON;"); err != nil {
		db.Close()
		return nil, fmt.Errorf("set pragmas: %w", err)
	}
	if err := db.Ping(); err != nil {
		db.Close()
		return nil, fmt.Errorf("ping: %w", err)
	}
	return db, nil
}

func Migrate(db *sql.DB) error {
	if _, err := db.Exec(`CREATE TABLE IF NOT EXISTS schema_migrations (
		version    TEXT PRIMARY KEY,
		applied_at DATETIME DEFAULT CURRENT_TIMESTAMP
	)`); err != nil {
		return fmt.Errorf("create schema_migrations: %w", err)
	}

	entries, err := fs.ReadDir(migrationsFS, "migrations")
	if err != nil {
		return fmt.Errorf("read migrations dir: %w", err)
	}

	var files []string
	for _, e := range entries {
		if !e.IsDir() && strings.HasSuffix(e.Name(), ".sql") {
			files = append(files, e.Name())
		}
	}
	sort.Strings(files)

	for _, name := range files {
		var count int
		if err := db.QueryRow("SELECT COUNT(*) FROM schema_migrations WHERE version = ?", name).Scan(&count); err != nil {
			return fmt.Errorf("check migration %s: %w", name, err)
		}
		if count > 0 {
			continue
		}

		data, err := migrationsFS.ReadFile("migrations/" + name)
		if err != nil {
			return fmt.Errorf("read migration %s: %w", name, err)
		}

		if _, err := db.Exec(string(data)); err != nil {
			return fmt.Errorf("apply migration %s: %w", name, err)
		}

		if _, err := db.Exec("INSERT INTO schema_migrations (version) VALUES (?)", name); err != nil {
			return fmt.Errorf("record migration %s: %w", name, err)
		}
	}
	return nil
}