// Package pgstore is the platform's Postgres access: migrations, the pool, and the queries the
// HTTP layer needs. It is the only package that speaks SQL.
package pgstore

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

	_ "github.com/jackc/pgx/v5/stdlib" // database/sql driver "pgx", used by goose only
	"github.com/pressly/goose/v3"
	"github.com/pressly/goose/v3/lock"
)

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

// Migrations exposes the embedded SQL for tests that check the set without a database.
func Migrations() fs.FS {
	sub, err := fs.Sub(migrationsFS, "migrations")
	if err != nil {
		panic(err) // the path is a compile-time constant of this package
	}
	return sub
}

// Migrate applies every pending migration and returns when the schema is current.
//
// It opens its OWN database/sql handle rather than borrowing the pgx pool: goose speaks
// database/sql, and a one-connection handle is what the session locker needs anyway. The lock is a
// Postgres advisory lock, so two instances rolling out at once serialize instead of racing.
func Migrate(ctx context.Context, dsn string) error {
	db, err := sql.Open("pgx", dsn)
	if err != nil {
		return fmt.Errorf("pgstore: open migration handle: %w", err)
	}
	defer db.Close()
	db.SetMaxOpenConns(1)

	locker, err := lock.NewPostgresSessionLocker()
	if err != nil {
		return fmt.Errorf("pgstore: locker: %w", err)
	}
	p, err := goose.NewProvider(goose.DialectPostgres, db, Migrations(), goose.WithSessionLocker(locker))
	if err != nil {
		return fmt.Errorf("pgstore: goose provider: %w", err)
	}
	if _, err := p.Up(ctx); err != nil {
		return fmt.Errorf("pgstore: migrate: %w", err)
	}
	return nil
}