package db

import (
	"database/sql"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"

	_ "modernc.org/sqlite"
)

type DB struct {
	*sql.DB
}

func (d *DB) SQLDB() *sql.DB {
	return d.DB
}

func Open(dbPath string) (*DB, error) {
	if err := os.MkdirAll(filepath.Dir(dbPath), 0700); err != nil {
		return nil, err
	}

	db, err := sql.Open("sqlite", dbPath+"?_journal_mode=WAL&_foreign_keys=ON&_busy_timeout=5000")
	if err != nil {
		return nil, fmt.Errorf("opening db: %w", err)
	}

	if _, err := db.Exec("PRAGMA foreign_keys = ON"); err != nil {
		db.Close()
		return nil, fmt.Errorf("enabling foreign_keys: %w", err)
	}

	return &DB{db}, nil
}

func (db *DB) Close() error {
	return db.DB.Close()
}

func (db *DB) RunMigrations() error {
	return db.runMigrationsInternal(migrationsFS, "migrations")
}

func (db *DB) runMigrationsInternal(mfs embedFS, migrationsRoot string) error {
	entries, err := mfs.ReadDir(migrationsRoot)
	if err != nil {
		return fmt.Errorf("reading migrations dir: %w", err)
	}

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

	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("creating schema_migrations table: %w", err)
	}

	for _, name := range names {
		var applied bool
		row := db.QueryRow("SELECT 1 FROM schema_migrations WHERE version = ?", name)
		if err := row.Scan(&applied); err == nil {
			applied = true
		}

		if applied {
			continue
		}

		data, err := mfs.ReadFile(filepath.Join(migrationsRoot, name))
		if err != nil {
			return fmt.Errorf("reading migration %s: %w", name, err)
		}

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

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

	return nil
}

type embedFS interface {
	ReadDir(name string) ([]os.DirEntry, error)
	ReadFile(name string) ([]byte, error)
}