package mijia

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/http/cookiejar"
	"net/url"
	"os"
	"path/filepath"
	"reflect"
	"strconv"
	"strings"
	"sync"
	"time"
)

const (
	defaultBaseURL         = "https://api.mijia.tech/app"
	defaultLoginURL        = "https://account.xiaomi.com/longPolling/loginUrl"
	defaultServiceLoginURL = "https://account.xiaomi.com/pass/serviceLogin"
	availabilityTTL        = 60 * time.Second
)

type Option func(*Client) error

// WithHTTPClient configures the HTTP transport used by the client.
func WithHTTPClient(httpClient *http.Client) Option {
	return func(client *Client) error {
		if httpClient == nil {
			return fmt.Errorf("HTTP client must not be nil")
		}
		client.httpClient = httpClient
		return nil
	}
}

// WithQRWriter configures where QR login output is written.
func WithQRWriter(writer io.Writer) Option {
	return func(client *Client) error {
		isNil := writer == nil
		if !isNil {
			value := reflect.ValueOf(writer)
			switch value.Kind() {
			case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice, reflect.UnsafePointer:
				isNil = value.IsNil()
			}
		}
		if isNil {
			return fmt.Errorf("QR writer must not be nil")
		}
		client.qrWriter = writer
		return nil
	}
}

type Client struct {
	authPath        string
	authMu          sync.RWMutex
	authData        AuthData
	loginMu         sync.Mutex
	httpClientMu    sync.RWMutex
	httpClient      *http.Client
	baseURL         string
	loginURL        string
	serviceLoginURL string
	locale          string
	qrWriter        io.Writer

	availabilityMu    sync.Mutex
	availability      bool
	availabilityValid bool
	availabilityAt    time.Time
}

func NewClient(authPath string, options ...Option) (*Client, error) {
	resolvedPath, err := resolveAuthPath(authPath)
	if err != nil {
		return nil, err
	}
	client := &Client{
		authPath:        resolvedPath,
		httpClient:      http.DefaultClient,
		baseURL:         defaultBaseURL,
		loginURL:        defaultLoginURL,
		serviceLoginURL: defaultServiceLoginURL,
		locale:          systemLocale(),
		qrWriter:        os.Stdout,
	}
	for _, option := range options {
		if option == nil {
			continue
		}
		if err := option(client); err != nil {
			return nil, err
		}
	}
	if err := client.loadAuthData(); err != nil {
		return nil, err
	}
	client.ensureIdentity()
	client.initSession()
	return client, nil
}

func resolveAuthPath(authPath string) (string, error) {
	if authPath == "" {
		home, err := os.UserHomeDir()
		if err != nil {
			return "", fmt.Errorf("resolve home directory: %w", err)
		}
		return filepath.Join(home, ".config", "mijia-api", "auth.json"), nil
	}
	info, err := os.Stat(authPath)
	if err == nil && info.IsDir() {
		return filepath.Join(authPath, "auth.json"), nil
	}
	if err != nil && !os.IsNotExist(err) {
		return "", fmt.Errorf("inspect auth path: %w", err)
	}
	return authPath, nil
}

func systemLocale() string {
	locale := strings.Split(os.Getenv("LC_ALL"), ".")[0]
	if locale == "" {
		locale = strings.Split(os.Getenv("LANG"), ".")[0]
	}
	if parts := strings.Split(locale, "_"); len(parts) == 2 && len(parts[1]) >= 2 {
		return parts[0] + "_" + strings.ToUpper(parts[1][:2])
	}
	return "zh_CN"
}

func (client *Client) initSession() {
	client.httpClientMu.Lock()
	defer client.httpClientMu.Unlock()
	client.httpClient = cloneHTTPClient(client.httpClient)
}

func cloneHTTPClient(httpClient *http.Client) *http.Client {
	clone := *httpClient
	clone.Jar, _ = cookiejar.New(nil)
	return &clone
}

func (client *Client) session() *http.Client {
	client.httpClientMu.RLock()
	defer client.httpClientMu.RUnlock()
	return client.httpClient
}

func (client *Client) newSession() *http.Client {
	return cloneHTTPClient(client.session())
}

func (client *Client) request(ctx context.Context, uri string, data any, refresh bool) (json.RawMessage, error) {
	if refresh {
		if err := client.refreshToken(ctx); err != nil {
			return nil, err
		}
	}
	payload, err := json.Marshal(data)
	if err != nil {
		return nil, fmt.Errorf("marshal request data: %w", err)
	}
	nonce, err := generateNonce()
	if err != nil {
		return nil, err
	}
	authData := client.AuthData()
	signedNonceValue, err := signedNonce(authData.Ssecurity, nonce)
	if err != nil {
		return nil, err
	}
	params, err := generateEncryptedParams(uri, http.MethodPost, signedNonceValue, nonce, string(payload), authData.Ssecurity)
	if err != nil {
		return nil, err
	}
	form := url.Values{
		"data":       {params.Data},
		"rc4_hash__": {params.RC4Hash},
		"signature":  {params.Signature},
		"ssecurity":  {params.Ssecurity},
		"_nonce":     {params.Nonce},
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, client.baseURL+uri, strings.NewReader(form.Encode()))
	if err != nil {
		return nil, fmt.Errorf("create API request: %w", err)
	}
	client.setAPIHeaders(req, authData)
	response, err := client.session().Do(req)
	if err != nil {
		return nil, fmt.Errorf("send API request: %w", err)
	}
	defer response.Body.Close()
	body, err := readHTTPResponse(response)
	if err != nil {
		return nil, fmt.Errorf("read API response: %w", err)
	}
	if response.StatusCode < 200 || response.StatusCode >= 300 {
		return nil, fmt.Errorf("API HTTP status %d: %s", response.StatusCode, strings.TrimSpace(string(body)))
	}
	result, err := decodeAPIResponse(authData.Ssecurity, nonce, body)
	if err != nil {
		return nil, fmt.Errorf("decode API response from %s: %w", uri, err)
	}
	return result, nil
}

func decodeAPIResponse(ssecurity, nonce string, body []byte) (json.RawMessage, error) {
	var envelope struct {
		Code    int             `json:"code"`
		Message string          `json:"message"`
		Desc    string          `json:"desc"`
		Result  json.RawMessage `json:"result"`
	}
	if err := json.Unmarshal(body, &envelope); err != nil {
		decrypted, decryptErr := decryptPayload(ssecurity, nonce, string(body))
		if decryptErr != nil {
			return nil, fmt.Errorf("decode API response: %w", decryptErr)
		}
		if err := json.Unmarshal([]byte(decrypted), &envelope); err != nil {
			return nil, fmt.Errorf("decode decrypted API response: %w", err)
		}
	}
	if envelope.Code != 0 || envelope.Result == nil {
		message := envelope.Message
		if message == "" {
			message = envelope.Desc
		}
		if message == "" {
			message = "未知错误"
		}
		return nil, &APIError{Code: envelope.Code, Message: message}
	}
	return envelope.Result, nil
}

func (client *Client) setAPIHeaders(request *http.Request, authData AuthData) {
	request.Header.Set("User-Agent", authData.UA)
	request.Header.Set("Accept-Encoding", "identity")
	request.Header.Set("Content-Type", "application/x-www-form-urlencoded")
	request.Header.Set("miot-accept-encoding", "GZIP")
	request.Header.Set("miot-encrypt-algorithm", "ENCRYPT-RC4")
	request.Header.Set("x-xiaomi-protocal-flag-cli", "PROTOCAL-HTTP2")
	request.Header.Set("Cookie", client.apiCookieHeader(authData))
}

func (client *Client) apiCookieHeader(authData AuthData) string {
	now := time.Now()
	_, offset := now.Zone()
	zoneName := now.Location().String()
	if zoneName == "Local" {
		zoneName, _ = now.Zone()
	}
	isDaylight, dstOffset := daylightValues(now)
	countryCode := "CN"
	if parts := strings.Split(client.locale, "_"); len(parts) == 2 {
		countryCode = parts[1]
	}
	timezone := fmt.Sprintf("GMT%+03d:%02d", offset/3600, abs(offset/60)%60)
	values := []string{
		"cUserId=" + authData.CUserID,
		"yetAnotherServiceToken=" + authData.yetAnotherServiceToken(),
		"serviceToken=" + authData.ServiceToken,
		"timezone_id=" + zoneName,
		"timezone=" + timezone,
		"is_daylight=" + strconv.Itoa(isDaylight),
		"dst_offset=" + strconv.Itoa(dstOffset),
		"channel=MI_APP_STORE",
		"countryCode=" + countryCode,
		"PassportDeviceId=" + authData.DeviceID,
		"locale=" + client.locale,
	}
	return strings.Join(values, ";")
}

func daylightValues(now time.Time) (int, int) {
	location := now.Location()
	dstOffset := 0
	if now.In(location).IsDST() {
		dstOffset = 60 * 60 * 1000
	}
	for date := time.Date(now.Year(), time.January, 1, 12, 0, 0, 0, location); date.Year() == now.Year(); date = date.AddDate(0, 0, 1) {
		if date.IsDST() {
			return 1, dstOffset
		}
	}
	return 0, dstOffset
}

func abs(value int) int {
	if value < 0 {
		return -value
	}
	return value
}

func (client *Client) Available(ctx context.Context) (bool, error) {
	if !client.AuthData().complete() {
		return false, nil
	}
	client.availabilityMu.Lock()
	defer client.availabilityMu.Unlock()
	if client.availabilityValid && time.Since(client.availabilityAt) < availabilityTTL {
		return client.availability, nil
	}

	_, err := client.request(ctx, "/v2/message/v2/check_new_msg", map[string]int64{"begin_at": time.Now().Unix() - 3600}, false)
	if err != nil {
		client.availability = false
		client.availabilityValid = false
		client.availabilityAt = time.Time{}
		return false, err
	}
	client.availability = true
	client.availabilityValid = true
	client.availabilityAt = time.Now()
	return true, nil
}