// Package store owns OpenMail's Postgres-backed persistence. This is the
// deliberate divergence from Mox: OpenMail keeps its own native, agent-shaped
// data model (see ARCHITECTURE.md §3) rather than embedding Mox's bstore/bbolt
// account store.
package store

import (
	"context"
	"embed"
	"fmt"
	"sort"
	"strings"

	"github.com/jackc/pgx/v5/pgxpool"
)

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

type Store struct {
	Pool *pgxpool.Pool
}

// Open connects to Postgres and verifies the connection.
func Open(ctx context.Context, databaseURL string) (*Store, error) {
	if databaseURL == "" {
		return nil, fmt.Errorf("store: DATABASE_URL is empty")
	}
	pool, err := pgxpool.New(ctx, databaseURL)
	if err != nil {
		return nil, fmt.Errorf("store: connect: %w", err)
	}
	if err := pool.Ping(ctx); err != nil {
		pool.Close()
		return nil, fmt.Errorf("store: ping: %w", err)
	}
	return &Store{Pool: pool}, nil
}

func (s *Store) Close() {
	if s.Pool != nil {
		s.Pool.Close()
	}
}

// Migrate applies any embedded migrations not yet recorded in schema_migrations,
// in filename order. Each migration runs in its own transaction.
func (s *Store) Migrate(ctx context.Context) error {
	_, err := s.Pool.Exec(ctx, `CREATE TABLE IF NOT EXISTS schema_migrations (
		version text PRIMARY KEY,
		applied_at timestamptz NOT NULL DEFAULT now()
	)`)
	if err != nil {
		return fmt.Errorf("migrate: ensure schema_migrations: %w", err)
	}

	entries, err := migrationsFS.ReadDir("migrations")
	if err != nil {
		return fmt.Errorf("migrate: read embedded migrations: %w", err)
	}
	names := make([]string, 0, len(entries))
	for _, e := range entries {
		if strings.HasSuffix(e.Name(), ".sql") {
			names = append(names, e.Name())
		}
	}
	sort.Strings(names)

	for _, name := range names {
		var exists bool
		if err := s.Pool.QueryRow(ctx,
			`SELECT EXISTS(SELECT 1 FROM schema_migrations WHERE version=$1)`, name,
		).Scan(&exists); err != nil {
			return fmt.Errorf("migrate: check %s: %w", name, err)
		}
		if exists {
			continue
		}
		sqlBytes, err := migrationsFS.ReadFile("migrations/" + name)
		if err != nil {
			return fmt.Errorf("migrate: read %s: %w", name, err)
		}
		tx, err := s.Pool.Begin(ctx)
		if err != nil {
			return fmt.Errorf("migrate: begin %s: %w", name, err)
		}
		if _, err := tx.Exec(ctx, string(sqlBytes)); err != nil {
			_ = tx.Rollback(ctx)
			return fmt.Errorf("migrate: apply %s: %w", name, err)
		}
		if _, err := tx.Exec(ctx, `INSERT INTO schema_migrations(version) VALUES($1)`, name); err != nil {
			_ = tx.Rollback(ctx)
			return fmt.Errorf("migrate: record %s: %w", name, err)
		}
		if err := tx.Commit(ctx); err != nil {
			return fmt.Errorf("migrate: commit %s: %w", name, err)
		}
	}
	return nil
}