// Package store owns the SelfPost SQLite database: the single file under /data
// that persists the administrator account, sending domains and applications,
// the send log and rate-limit settings (spec 9). It exposes typed queries so
// the rest of the panel never builds SQL by hand.
package store

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

	_ "modernc.org/sqlite" // pure-Go SQLite driver (no cgo), keeps the static build
)

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

// Store wraps the database connection pool.
type Store struct {
	db *sql.DB
}

// Open opens (creating if needed) the SQLite database at path, enables WAL and
// foreign keys, and applies any pending migrations. The caller owns Close.
func Open(path string) (*Store, error) {
	// _pragma parameters are applied on every pooled connection by the driver,
	// so foreign-key enforcement and WAL survive connection churn.
	dsn := fmt.Sprintf("file:%s?_pragma=journal_mode(WAL)&_pragma=busy_timeout(5000)&_pragma=foreign_keys(ON)", path)
	db, err := sql.Open("sqlite", dsn)
	if err != nil {
		return nil, fmt.Errorf("open database: %w", err)
	}
	// modernc's driver serializes writes anyway; a small pool avoids
	// "database is locked" surprises under WAL.
	db.SetMaxOpenConns(1)

	s := &Store{db: db}
	if err := s.migrate(); err != nil {
		db.Close()
		return nil, err
	}
	return s, nil
}

// Close closes the underlying database.
func (s *Store) Close() error {
	return s.db.Close()
}

// migrate applies embedded migrations in filename order, tracking progress via
// SQLite's PRAGMA user_version so each migration runs at most once.
func (s *Store) migrate() error {
	entries, err := fs.ReadDir(migrationsFS, "migrations")
	if err != nil {
		return fmt.Errorf("read migrations: %w", err)
	}
	names := make([]string, 0, len(entries))
	for _, e := range entries {
		if !e.IsDir() {
			names = append(names, e.Name())
		}
	}
	sort.Strings(names)

	var version int
	if err := s.db.QueryRow("PRAGMA user_version").Scan(&version); err != nil {
		return fmt.Errorf("read schema version: %w", err)
	}

	for i, name := range names {
		target := i + 1
		if target <= version {
			continue
		}
		sqlBytes, err := migrationsFS.ReadFile("migrations/" + name)
		if err != nil {
			return fmt.Errorf("read migration %s: %w", name, err)
		}
		tx, err := s.db.Begin()
		if err != nil {
			return fmt.Errorf("begin migration %s: %w", name, err)
		}
		if _, err := tx.Exec(string(sqlBytes)); err != nil {
			tx.Rollback()
			return fmt.Errorf("apply migration %s: %w", name, err)
		}
		// PRAGMA does not accept a bound parameter, and target is a trusted
		// loop index, so formatting it in is safe.
		if _, err := tx.Exec(fmt.Sprintf("PRAGMA user_version = %d", target)); err != nil {
			tx.Rollback()
			return fmt.Errorf("bump schema version for %s: %w", name, err)
		}
		if err := tx.Commit(); err != nil {
			return fmt.Errorf("commit migration %s: %w", name, err)
		}
	}
	return nil
}