package postgres

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

	_ "github.com/lib/pq"
)

const initTimeout = 5 * time.Second

var (
	sqlOpen = sql.Open
	pingDB  = func(ctx context.Context, db *sql.DB) error { return db.PingContext(ctx) }
)

// ConnConfig describes the minimal connection settings shared by feedkit's
// Postgres readers and writers.
type ConnConfig struct {
	URI      string
	Username string
	Password string
}

// BuildDSN validates a Postgres URI and injects credentials into it.
func BuildDSN(cfg ConnConfig) (string, error) {
	u, err := url.Parse(strings.TrimSpace(cfg.URI))
	if err != nil {
		return "", fmt.Errorf("invalid uri: %w", err)
	}
	if u.Scheme == "" {
		return "", fmt.Errorf("invalid uri: missing scheme")
	}
	if u.Host == "" {
		return "", fmt.Errorf("invalid uri: missing host")
	}
	u.User = url.UserPassword(cfg.Username, cfg.Password)
	return u.String(), nil
}

// Open builds a DSN, opens a database handle, and verifies connectivity with a
// bounded ping before returning the handle.
func Open(ctx context.Context, cfg ConnConfig) (*sql.DB, error) {
	dsn, err := BuildDSN(cfg)
	if err != nil {
		return nil, err
	}

	db, err := sqlOpen("postgres", dsn)
	if err != nil {
		return nil, err
	}

	pingCtx, cancel := context.WithTimeout(ctx, initTimeout)
	defer cancel()

	if err := pingDB(pingCtx, db); err != nil {
		_ = db.Close()
		return nil, err
	}

	return db, nil
}