package db

import (
	"context"
	"database/sql"
	"fmt"
	"log/slog"
	"net/url"
	"strings"
	"time"

	_ "github.com/jackc/pgx/v5/stdlib"
)

// DBConfig holds database configuration.
type DBConfig struct {
	DSN             string        // Data Source Name (PostgreSQL connection string)
	MaxOpenConns    int           // Maximum number of open connections
	MaxIdleConns    int           // Maximum number of idle connections
	ConnMaxLifetime time.Duration // Maximum lifetime of connections
	ConnMaxIdleTime time.Duration // Maximum idle time for connections
}

// DefaultDBConfig returns a DBConfig with sensible defaults for PostgreSQL.
func DefaultDBConfig(dsn string) *DBConfig {
	return &DBConfig{
		DSN:             dsn,
		MaxOpenConns:    25,
		MaxIdleConns:    10,
		ConnMaxLifetime: 30 * time.Minute,
		ConnMaxIdleTime: 5 * time.Minute,
	}
}

// ensureSearchPath appends search_path with all module schemas to the DSN if
// not already present, so every connection in the pool resolves module-schema
// tables without qualification (Decision 113).
func ensureSearchPath(dsn string) string {
	const moduleSearchPath = "identity,organization,entitlements,billing,cooperative,audit,integration,stripe,public"
	u, err := url.Parse(dsn)
	if err != nil || u.Scheme == "" {
		// Key=value DSN format — append if not already set.
		if !strings.Contains(dsn, "search_path") {
			return dsn + " search_path=" + moduleSearchPath
		}
		return dsn
	}
	// URI format — append as query parameter.
	q := u.Query()
	if q.Get("search_path") == "" {
		q.Set("search_path", moduleSearchPath)
		u.RawQuery = q.Encode()
	}
	return u.String()
}

// openAndConfigureDB opens the database connection and configures the connection pool.
func openAndConfigureDB(config *DBConfig) (*sql.DB, error) {
	db, err := sql.Open("pgx", ensureSearchPath(config.DSN))
	if err != nil {
		return nil, fmt.Errorf("failed to open database: %w", err)
	}

	// Configure connection pool
	db.SetMaxOpenConns(config.MaxOpenConns)
	db.SetMaxIdleConns(config.MaxIdleConns)
	db.SetConnMaxLifetime(config.ConnMaxLifetime)
	db.SetConnMaxIdleTime(config.ConnMaxIdleTime)

	return db, nil
}

// ConnectPlain opens a database connection without the custom search_path.
// Use this for migrations — the custom search_path causes a pgx/PG18
// interaction that silently drops tables from multi-statement DDL.
func ConnectPlain(ctx context.Context, logger *slog.Logger, config *DBConfig) (*sql.DB, error) {
	db, err := sql.Open("pgx", config.DSN)
	if err != nil {
		return nil, fmt.Errorf("failed to open database: %w", err)
	}
	db.SetMaxOpenConns(config.MaxOpenConns)
	db.SetMaxIdleConns(config.MaxIdleConns)
	db.SetConnMaxLifetime(config.ConnMaxLifetime)
	db.SetConnMaxIdleTime(config.ConnMaxIdleTime)
	if err := db.PingContext(ctx); err != nil {
		db.Close()
		return nil, fmt.Errorf("failed to connect to database: %w", err)
	}
	logger.Info("database connection established (plain)",
		slog.String("dsn", config.DSN))
	return db, nil
}

// Connect initializes and returns a new database connection pool.
// This is the basic connection function without any automatic operations.
func Connect(ctx context.Context, logger *slog.Logger, config *DBConfig) (*sql.DB, error) {
	db, err := openAndConfigureDB(config)
	if err != nil {
		return nil, err
	}

	if err := db.PingContext(ctx); err != nil {
		db.Close()
		return nil, fmt.Errorf("failed to connect to database: %w", err)
	}

	logger.Info("database connection established",
		slog.String("dsn", config.DSN),
		slog.Int("max_open_conns", config.MaxOpenConns),
		slog.Int("max_idle_conns", config.MaxIdleConns))

	return db, nil
}

// ConnectAndMigrate initializes a database connection and automatically runs migrations.
// The sources parameter specifies migration sources in dependency order.
//
// Migrations run on a separate connection WITHOUT the custom search_path to
// avoid a pgx/PG18 interaction where setting module schemas in the search_path
// at connection time causes multi-statement DDL to silently lose tables. After
// migrations complete, the returned connection uses the full search_path for
// application queries.
func ConnectAndMigrate(ctx context.Context, logger *slog.Logger, config *DBConfig, sources []MigrationSource) (*sql.DB, error) {
	// Run migrations on a plain connection (no custom search_path).
	migDB, err := ConnectPlain(ctx, logger, config)
	if err != nil {
		return nil, err
	}
	if err := RunMigrations(migDB, sources); err != nil {
		migDB.Close()
		return nil, fmt.Errorf("failed to run migrations: %w", err)
	}
	migDB.Close()

	// Now open the application connection with full search_path.
	db, err := Connect(ctx, logger, config)
	if err != nil {
		return nil, err
	}

	logger.Info("database migrations applied")
	return db, nil
}