// Package config loads runtime settings from the environment, optionally
// seeded from a .env file sitting next to the binary or at the module root.
package config

import (
	"bufio"
	"fmt"
	"net"
	"net/url"
	"os"
	"path/filepath"
	"strings"
)

// Config holds everything the API needs to start.
type Config struct {
	DatabaseURL string
	Port        string
	CORSOrigins []string
}

// Load reads .env (if present) into the process environment, then builds a
// Config. Real environment variables always win over .env entries, so
// container and CI overrides behave the way people expect.
func Load() (*Config, error) {
	LoadDotEnv()

	cfg := &Config{
		Port:        envOr("PORT", "8080"),
		CORSOrigins: splitAndTrim(envOr("CORS_ORIGINS", "http://localhost:4200")),
	}

	if raw := os.Getenv("DATABASE_URL"); raw != "" {
		cfg.DatabaseURL = raw
	} else {
		user := envOr("DB_USER", "postgres")
		pass := os.Getenv("DB_PASSWORD")
		host := envOr("DB_HOST", "localhost")
		port := envOr("DB_PORT", "5432")
		name := envOr("DB_NAME", "travelhub")
		ssl := envOr("DB_SSLMODE", "disable")

		if pass == "" {
			return nil, fmt.Errorf("database password is not set: define DATABASE_URL or DB_PASSWORD (see .env.example)")
		}

		// url.UserPassword escapes credentials for us, which matters because
		// passwords routinely contain @ : / and other reserved characters.
		cfg.DatabaseURL = (&url.URL{
			Scheme:   "postgres",
			User:     url.UserPassword(user, pass),
			Host:     net.JoinHostPort(host, port),
			Path:     "/" + name,
			RawQuery: "sslmode=" + ssl,
		}).String()
	}

	return cfg, nil
}

// LoadDotEnv walks up from the working directory looking for a .env file and
// applies any keys that are not already set in the environment. Load calls it;
// it is exported so tests can pick up the same local credentials without
// building a whole Config.
func LoadDotEnv() {
	dir, err := os.Getwd()
	if err != nil {
		return
	}

	for i := 0; i < 4; i++ {
		path := filepath.Join(dir, ".env")
		if applyEnvFile(path) {
			return
		}
		parent := filepath.Dir(dir)
		if parent == dir {
			return
		}
		dir = parent
	}
}

// applyEnvFile reads one .env file. It reports whether the file existed.
func applyEnvFile(path string) bool {
	f, err := os.Open(path)
	if err != nil {
		return false
	}
	defer f.Close()

	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		key, value, found := strings.Cut(line, "=")
		if !found {
			continue
		}
		key = strings.TrimSpace(key)
		value = strings.TrimSpace(value)

		// Allow quoted values so passwords may contain leading/trailing spaces.
		if len(value) >= 2 {
			if (value[0] == '"' && value[len(value)-1] == '"') ||
				(value[0] == '\'' && value[len(value)-1] == '\'') {
				value = value[1 : len(value)-1]
			}
		}

		if _, exists := os.LookupEnv(key); !exists {
			os.Setenv(key, value)
		}
	}
	return true
}

func envOr(key, fallback string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return fallback
}

func splitAndTrim(s string) []string {
	parts := strings.Split(s, ",")
	out := make([]string, 0, len(parts))
	for _, p := range parts {
		if p = strings.TrimSpace(p); p != "" {
			out = append(out, p)
		}
	}
	return out
}