package media

import (
	"errors"
	"fmt"
	"io"
	"net"
	"net/url"
	"os"
	"path/filepath"
	"strings"
	"time"
)

var ErrUnsafeControlAPI = errors.New("MediaMTX Control API 必须使用本机回环地址")

type RuntimeConfig struct {
	Binary       string
	ConfigPath   string
	APIBase      string
	PollInterval time.Duration
	StartTimeout time.Duration
}

func ConfigFromEnvironment() (RuntimeConfig, error) {
	c := RuntimeConfig{
		Binary: strings.TrimSpace(os.Getenv("SENSE_MEDIAMTX_BINARY")), ConfigPath: strings.TrimSpace(os.Getenv("SENSE_MEDIAMTX_CONFIG")),
		APIBase: strings.TrimSpace(os.Getenv("SENSE_MEDIAMTX_API")), PollInterval: 5 * time.Second, StartTimeout: 8 * time.Second,
	}
	if c.APIBase == "" {
		c.APIBase = "http://127.0.0.1:9997"
	}
	if err := validateControlAPI(c.APIBase); err != nil {
		return RuntimeConfig{}, err
	}
	if c.Binary != "" && c.ConfigPath == "" {
		return RuntimeConfig{}, errors.New("SENSE_MEDIAMTX_CONFIG is required when SENSE_MEDIAMTX_BINARY is configured")
	}
	return c, nil
}

func validateControlAPI(value string) error {
	u, err := url.Parse(value)
	if err != nil || u.Scheme != "http" || u.User != nil || u.RawQuery != "" || u.Fragment != "" || u.Path != "" {
		return ErrUnsafeControlAPI
	}
	host := u.Hostname()
	ip := net.ParseIP(host)
	if host != "localhost" && (ip == nil || !ip.IsLoopback()) {
		return ErrUnsafeControlAPI
	}
	return nil
}

func RenderBaseConfig(w io.Writer, apiBase string) error {
	if err := validateControlAPI(apiBase); err != nil {
		return err
	}
	u, _ := url.Parse(apiBase)
	_, err := fmt.Fprintf(w, "logLevel: info\napi: true\napiAddress: %s\nmetrics: false\npaths: {}\n", u.Host)
	return err
}

func EnsureBaseConfig(path, apiBase string) error {
	if path == "" {
		return errors.New("MediaMTX config path is empty")
	}
	if _, err := os.Stat(path); err == nil {
		return nil
	} else if !errors.Is(err, os.ErrNotExist) {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(path), 0o750); err != nil {
		return err
	}
	temporary := path + ".tmp"
	f, err := os.OpenFile(temporary, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0o600)
	if err != nil {
		return err
	}
	writeErr := RenderBaseConfig(f, apiBase)
	closeErr := f.Close()
	if writeErr != nil || closeErr != nil {
		_ = os.Remove(temporary)
		return errors.Join(writeErr, closeErr)
	}
	if err = os.Rename(temporary, path); err != nil {
		_ = os.Remove(temporary)
	}
	return err
}