package sqlite

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

	_ "modernc.org/sqlite"
)

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

// DB wraps a SQLite connection and domain helpers.
type DB struct {
	SQL    *sql.DB
	Secret []byte // AES-256 key material for connection tokens (derived/padded)
}

// Open opens (or creates) the database at path and runs migrations.
func Open(path string, secret []byte) (*DB, error) {
	if path == "" {
		return nil, fmt.Errorf("sqlite: path required")
	}
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return nil, fmt.Errorf("sqlite: create dir: %w", err)
	}
	sqlDB, err := sql.Open("sqlite", path+"?_pragma=foreign_keys(1)&_pragma=busy_timeout(5000)&_pragma=journal_mode(WAL)")
	if err != nil {
		return nil, fmt.Errorf("sqlite: open: %w", err)
	}
	sqlDB.SetMaxOpenConns(1) // SQLite writer safety
	if err := sqlDB.Ping(); err != nil {
		_ = sqlDB.Close()
		return nil, fmt.Errorf("sqlite: ping: %w", err)
	}
	db := &DB{SQL: sqlDB, Secret: normalizeSecret(secret)}
	if err := db.migrate(); err != nil {
		_ = sqlDB.Close()
		return nil, err
	}
	return db, nil
}

// Close closes the underlying connection.
func (db *DB) Close() error {
	if db == nil || db.SQL == nil {
		return nil
	}
	return db.SQL.Close()
}

func (db *DB) migrate() error {
	if _, err := db.SQL.Exec(`CREATE TABLE IF NOT EXISTS schema_migrations (
		name TEXT PRIMARY KEY,
		applied_at TEXT NOT NULL
	)`); err != nil {
		return fmt.Errorf("sqlite: schema_migrations: %w", err)
	}

	entries, err := migrationFS.ReadDir("migrations")
	if err != nil {
		return fmt.Errorf("sqlite: list migrations: %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)

	for _, name := range names {
		var exists string
		err := db.SQL.QueryRow(`SELECT name FROM schema_migrations WHERE name = ?`, name).Scan(&exists)
		if err == nil {
			continue
		}
		if err != sql.ErrNoRows {
			return fmt.Errorf("sqlite: check migration %s: %w", name, err)
		}
		body, err := migrationFS.ReadFile("migrations/" + name)
		if err != nil {
			return fmt.Errorf("sqlite: read migration %s: %w", name, err)
		}
		tx, err := db.SQL.Begin()
		if err != nil {
			return err
		}
		if _, err := tx.Exec(string(body)); err != nil {
			_ = tx.Rollback()
			return fmt.Errorf("sqlite: apply %s: %w", name, err)
		}
		if _, err := tx.Exec(`INSERT INTO schema_migrations(name, applied_at) VALUES(?, ?)`,
			name, time.Now().UTC().Format(time.RFC3339Nano)); err != nil {
			_ = tx.Rollback()
			return fmt.Errorf("sqlite: record %s: %w", name, err)
		}
		if err := tx.Commit(); err != nil {
			return err
		}
	}
	return nil
}

func formatTime(t time.Time) string {
	if t.IsZero() {
		return ""
	}
	return t.UTC().Format(time.RFC3339Nano)
}

func parseTime(s string) time.Time {
	s = strings.TrimSpace(s)
	if s == "" {
		return time.Time{}
	}
	for _, layout := range []string{time.RFC3339Nano, time.RFC3339} {
		if t, err := time.Parse(layout, s); err == nil {
			return t.UTC()
		}
	}
	return time.Time{}
}