package tencentim

import (
	"bytes"
	"compress/zlib"
	"context"
	"crypto/hmac"
	"crypto/rand"
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"math/big"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"

	"chatapp3-golang/internal/config"
)

var ErrNotConfigured = errors.New("tencent im config is missing")

type Client struct {
	cfg        config.TencentIMConfig
	httpClient *http.Client
}

type apiResponse struct {
	ActionStatus string `json:"ActionStatus"`
	ErrorCode    int    `json:"ErrorCode"`
	ErrorInfo    string `json:"ErrorInfo"`
	GroupID      string `json:"GroupId"`
}

type apiError struct {
	code   int
	status string
	info   string
}

func (e *apiError) Error() string {
	return fmt.Sprintf("tencent im error code=%d status=%s info=%s", e.code, e.status, e.info)
}

func NewClient(cfg config.TencentIMConfig) *Client {
	timeoutSeconds := cfg.RequestTimeoutSeconds
	if timeoutSeconds <= 0 {
		timeoutSeconds = 8
	}
	return &Client{
		cfg: cfg,
		httpClient: &http.Client{
			Timeout: time.Duration(timeoutSeconds) * time.Second,
		},
	}
}

func (c *Client) CreateAVChatRoom(ctx context.Context, groupID string, groupName string) (string, error) {
	groupID = strings.TrimSpace(groupID)
	groupName = strings.TrimSpace(groupName)
	if groupID == "" {
		return "", errors.New("group id is required")
	}
	if groupName == "" {
		groupName = groupID
	}
	resp, err := c.post(ctx, "/v4/group_open_http_svc/create_group", map[string]any{
		"Type":            "AVChatRoom",
		"GroupId":         groupID,
		"Name":            groupName,
		"ApplyJoinOption": "FreeAccess",
	})
	if err != nil {
		if isTencentIMGroupAlreadyExists(err) {
			return groupID, nil
		}
		return "", err
	}
	if strings.TrimSpace(resp.GroupID) != "" {
		return strings.TrimSpace(resp.GroupID), nil
	}
	return groupID, nil
}

func (c *Client) SendCustomGroupMessage(ctx context.Context, groupID string, body any) error {
	groupID = strings.TrimSpace(groupID)
	if groupID == "" {
		return errors.New("group id is required")
	}
	data, err := json.Marshal(body)
	if err != nil {
		return err
	}
	_, err = c.post(ctx, "/v4/group_open_http_svc/send_group_msg", map[string]any{
		"GroupId": groupID,
		"Random":  randomInt31(),
		"MsgBody": []map[string]any{
			{
				"MsgType": "TIMCustomElem",
				"MsgContent": map[string]any{
					"Data":  string(data),
					"Desc":  "customBody",
					"Sound": "dingdong.aiff",
				},
			},
		},
	})
	return err
}

func (c *Client) Post(ctx context.Context, path string, payload any) error {
	_, err := c.post(ctx, path, payload)
	return err
}

func (c *Client) post(ctx context.Context, path string, payload any) (*apiResponse, error) {
	if c == nil || c.cfg.AppID <= 0 || strings.TrimSpace(c.cfg.Key) == "" || strings.TrimSpace(c.cfg.Identifier) == "" {
		return nil, ErrNotConfigured
	}
	baseEndpoint := strings.TrimRight(strings.TrimSpace(c.cfg.BaseEndpoint), "/")
	if baseEndpoint == "" {
		baseEndpoint = "https://console.tim.qq.com"
	}
	expireSeconds := c.cfg.UserSigExpireSeconds
	if expireSeconds <= 0 {
		expireSeconds = 7200000
	}
	userSig, err := genTencentIMUserSig(c.cfg.AppID, strings.TrimSpace(c.cfg.Key), strings.TrimSpace(c.cfg.Identifier), expireSeconds, time.Now().Unix())
	if err != nil {
		return nil, err
	}
	query := url.Values{}
	query.Set("sdkappid", strconv.FormatInt(c.cfg.AppID, 10))
	query.Set("identifier", strings.TrimSpace(c.cfg.Identifier))
	query.Set("usersig", userSig)
	query.Set("random", strconv.FormatInt(randomInt31(), 10))
	query.Set("contenttype", "json")

	body, err := json.Marshal(payload)
	if err != nil {
		return nil, err
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, baseEndpoint+path+"?"+query.Encode(), bytes.NewReader(body))
	if err != nil {
		return nil, err
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	respBody, readErr := io.ReadAll(resp.Body)
	if readErr != nil {
		return nil, readErr
	}
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		return nil, fmt.Errorf("tencent im http status %d: %s", resp.StatusCode, string(respBody))
	}
	var apiResp apiResponse
	if err := json.Unmarshal(respBody, &apiResp); err != nil {
		return nil, fmt.Errorf("decode tencent im response: %w body=%s", err, string(respBody))
	}
	if apiResp.ErrorCode != 0 || (apiResp.ActionStatus != "" && !strings.EqualFold(apiResp.ActionStatus, "OK")) {
		if strings.TrimSpace(apiResp.ErrorInfo) == "" {
			apiResp.ErrorInfo = string(respBody)
		}
		return nil, &apiError{code: apiResp.ErrorCode, status: apiResp.ActionStatus, info: apiResp.ErrorInfo}
	}
	return &apiResp, nil
}

func isTencentIMGroupAlreadyExists(err error) bool {
	var apiErr *apiError
	if !errors.As(err, &apiErr) {
		return false
	}
	if apiErr.code == 10021 || apiErr.code == 10025 {
		return true
	}
	info := strings.ToLower(strings.TrimSpace(apiErr.info))
	return strings.Contains(info, "group id in use") || strings.Contains(info, "group id has been used")
}

func genTencentIMUserSig(appID int64, key string, identifier string, expireSeconds int64, now int64) (string, error) {
	if appID <= 0 || strings.TrimSpace(key) == "" || strings.TrimSpace(identifier) == "" {
		return "", ErrNotConfigured
	}
	if expireSeconds <= 0 {
		expireSeconds = 7200000
	}
	content := "TLS.identifier:" + identifier + "\n" +
		"TLS.sdkappid:" + strconv.FormatInt(appID, 10) + "\n" +
		"TLS.time:" + strconv.FormatInt(now, 10) + "\n" +
		"TLS.expire:" + strconv.FormatInt(expireSeconds, 10) + "\n"
	mac := hmac.New(sha256.New, []byte(key))
	_, _ = mac.Write([]byte(content))
	sig := base64.StdEncoding.EncodeToString(mac.Sum(nil))

	raw, err := json.Marshal(map[string]any{
		"TLS.ver":        "2.0",
		"TLS.identifier": identifier,
		"TLS.sdkappid":   appID,
		"TLS.expire":     expireSeconds,
		"TLS.time":       now,
		"TLS.sig":        sig,
	})
	if err != nil {
		return "", err
	}
	var compressed bytes.Buffer
	writer := zlib.NewWriter(&compressed)
	if _, err := writer.Write(raw); err != nil {
		_ = writer.Close()
		return "", err
	}
	if err := writer.Close(); err != nil {
		return "", err
	}
	return strings.NewReplacer("+", "*", "/", "-", "=", "_").Replace(base64.StdEncoding.EncodeToString(compressed.Bytes())), nil
}

func randomInt31() int64 {
	n, err := rand.Int(rand.Reader, big.NewInt(2147483647))
	if err != nil {
		return time.Now().UnixNano() & 0x7fffffff
	}
	return n.Int64()
}