package lagoon

import (
	"context"
	"database/sql"
	"fmt"
	"strings"

	"git.golem15.com/golem15/summercms/backpack"
	"git.golem15.com/golem15/summercms/compass"
	_ "github.com/jackc/pgx/v5/stdlib"
	"gorm.io/driver/postgres"
	"gorm.io/gorm"
)

const (
	requiredLocaleProvider = "i"
	requiredICULocale      = "pl-PL"
)

// Open pings dsn through pgx stdlib, requires Postgres 16 ICU pl-PL, and
// returns that exact *sql.DB plus a GORM handle opened on it.
//
// Phase 11 owns a separate pgxpool.Pool for River LISTEN/NOTIFY. Do not
// create that listener pool here; application queries share this *sql.DB.
func Open(ctx context.Context, dsn string) (*sql.DB, *gorm.DB, error) {
	dsn = strings.TrimSpace(dsn)
	if dsn == "" {
		return nil, nil, fmt.Errorf("lagoon: database.dsn is empty (set SUMMER_DATABASE__DSN)")
	}
	sqlDB, err := sql.Open("pgx", dsn)
	if err != nil {
		return nil, nil, fmt.Errorf("lagoon: open postgres: %w", err)
	}
	if err := sqlDB.PingContext(ctx); err != nil {
		_ = sqlDB.Close()
		return nil, nil, fmt.Errorf("lagoon: ping postgres: %w", err)
	}
	if err := CheckLocale(ctx, sqlDB); err != nil {
		_ = sqlDB.Close()
		return nil, nil, err
	}
	gdb, err := gormFromSQL(sqlDB)
	if err != nil {
		_ = sqlDB.Close()
		return nil, nil, err
	}
	return sqlDB, gdb, nil
}

// Use pings an existing pool, requires ICU pl-PL, and returns a GORM handle
// opened on that exact *sql.DB. Callers that already hold a pool (tests,
// the app boot seam) must not open a second connection.
func Use(ctx context.Context, sqlDB *sql.DB) (*gorm.DB, error) {
	if sqlDB == nil {
		return nil, fmt.Errorf("lagoon: sql db is nil")
	}
	if err := sqlDB.PingContext(ctx); err != nil {
		return nil, fmt.Errorf("lagoon: ping postgres: %w", err)
	}
	if err := CheckLocale(ctx, sqlDB); err != nil {
		return nil, err
	}
	return gormFromSQL(sqlDB)
}

func gormFromSQL(sqlDB *sql.DB) (*gorm.DB, error) {
	gdb, err := gorm.Open(postgres.New(postgres.Config{Conn: sqlDB}), &gorm.Config{})
	if err != nil {
		return nil, fmt.Errorf("lagoon: gorm open: %w", err)
	}
	got, err := gdb.DB()
	if err != nil {
		return nil, fmt.Errorf("lagoon: gorm sql handle: %w", err)
	}
	if got != sqlDB {
		return nil, fmt.Errorf("lagoon: GORM is not using the shared *sql.DB")
	}
	return gdb, nil
}

// OpenFromApp reads database.dsn from app config and opens the shared pool.
func OpenFromApp(ctx context.Context, app *backpack.App) (*sql.DB, *gorm.DB, error) {
	if app == nil || app.Config == nil {
		return nil, nil, fmt.Errorf("lagoon: app config is missing")
	}
	return Open(ctx, DSN(app.Config))
}

// DSN returns database.dsn from layered config (env SUMMER_DATABASE__DSN).
func DSN(cfg *compass.Config) string {
	if cfg == nil {
		return ""
	}
	return strings.TrimSpace(cfg.String("database.dsn"))
}

// Publish stores the shared SQL pool and GORM handle on the app. Both
// handles refer to the same *sql.DB.
func Publish(app *backpack.App, sqlDB *sql.DB, gdb *gorm.DB) error {
	if app == nil {
		return fmt.Errorf("lagoon: app is nil")
	}
	if sqlDB == nil || gdb == nil {
		return fmt.Errorf("lagoon: database handles are nil")
	}
	if err := app.Publish(sqlDB); err != nil {
		return err
	}
	return app.Publish(gdb)
}

// CheckLocale fails unless the connected database uses ICU locale pl-PL.
func CheckLocale(ctx context.Context, db *sql.DB) error {
	if db == nil {
		return fmt.Errorf("lagoon: sql db is nil")
	}
	var provider, icu string
	err := db.QueryRowContext(ctx, `
SELECT datlocprovider::text, COALESCE(daticulocale, '')
FROM pg_database
WHERE datname = current_database()`).Scan(&provider, &icu)
	if err != nil {
		return fmt.Errorf("lagoon: read database locale: %w", err)
	}
	return checkLocale(provider, icu)
}

func checkLocale(provider, icu string) error {
	provider = strings.TrimSpace(provider)
	icu = strings.TrimSpace(icu)
	if provider == requiredLocaleProvider && icu == requiredICULocale {
		return nil
	}
	return fmt.Errorf("lagoon: database locale must be ICU pl-PL (datlocprovider=%q, daticulocale=%q); got provider %q locale %q. Create the database with: CREATE DATABASE ... TEMPLATE template0 ENCODING 'UTF8' LOCALE_PROVIDER icu ICU_LOCALE 'pl-PL'", requiredLocaleProvider, requiredICULocale, provider, icu)
}