package adapter

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"
)

const safewAPIBase = "https://api.safew.bot"

type SafeWSender struct {
	apiBase string
}

type safewConfig struct {
	Token  string          `json:"token"`
	ChatID json.RawMessage `json:"chat_id"`
}

type safewMessage struct {
	ChatID    string `json:"chat_id"`
	Text      string `json:"text"`
	ParseMode string `json:"parse_mode"`
}

type safewAPIResponse struct {
	OK          bool   `json:"ok"`
	Description string `json:"description"`
	ErrorMsg    string `json:"error_msg"`
}

func (s *SafeWSender) Type() string { return "safew" }

func (s *SafeWSender) Send(title, content string, config json.RawMessage) error {
	var cfg safewConfig
	if err := json.Unmarshal(config, &cfg); err != nil {
		return fmt.Errorf("parse safew config: %w", err)
	}
	token := strings.TrimSpace(cfg.Token)
	if token == "" {
		return fmt.Errorf("safew: token is required")
	}
	chatID, err := parseSafewChatID(cfg.ChatID)
	if err != nil {
		return err
	}

	payload := safewMessage{
		ChatID:    chatID,
		Text:      "*" + escapeMarkdownV2(title) + "*\n" + escapeMarkdownV2(content),
		ParseMode: "MarkdownV2",
	}
	body, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("safew marshal: %w", err)
	}

	resp, err := http.Post(s.endpoint(token), "application/json", bytes.NewReader(body))
	if err != nil {
		return fmt.Errorf("safew send: %w", err)
	}
	defer resp.Body.Close()

	respBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return fmt.Errorf("safew read: %w", err)
	}
	if resp.StatusCode >= 400 {
		desc := safewErrorDescription(respBody)
		if desc != "" {
			return fmt.Errorf("safew returned status %d: %s", resp.StatusCode, desc)
		}
		return fmt.Errorf("safew returned status %d", resp.StatusCode)
	}

	var api safewAPIResponse
	if err := json.Unmarshal(respBody, &api); err != nil {
		return fmt.Errorf("safew decode: %w", err)
	}
	if !api.OK {
		desc := api.Description
		if desc == "" {
			desc = "ok=false"
		}
		return fmt.Errorf("safew: %s", desc)
	}
	return nil
}

func (s *SafeWSender) endpoint(token string) string {
	return s.methodURL(token, "sendMessage")
}

func (s *SafeWSender) methodURL(token, method string) string {
	base := s.apiBase
	if base == "" {
		base = safewAPIBase
	}
	return strings.TrimRight(base, "/") + "/bot" + token + "/" + method
}

type SafewAuthError struct {
	Description string
}

func (e *SafewAuthError) Error() string {
	if e.Description == "" {
		return "safew unauthorized"
	}
	return e.Description
}

var safewLongPollClient = &http.Client{Timeout: 45 * time.Second}

func (s *SafeWSender) PollGroupChats(token string, offset int64, timeout int) ([]SafewChat, int64, error) {
	token = strings.TrimSpace(token)
	if token == "" {
		return nil, offset, fmt.Errorf("safew: token is required")
	}
	payload := map[string]any{
		"timeout": timeout,
		"limit":   100,
	}
	if offset > 0 {
		payload["offset"] = offset
	}
	reqBody, _ := json.Marshal(payload)
	resp, err := safewLongPollClient.Post(s.methodURL(token, "getUpdates"), "application/json", bytes.NewReader(reqBody))
	if err != nil {
		return nil, offset, fmt.Errorf("safew getUpdates: %w", err)
	}
	defer resp.Body.Close()
	respBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, offset, fmt.Errorf("safew getUpdates read: %w", err)
	}
	if resp.StatusCode == http.StatusUnauthorized {
		return nil, offset, &SafewAuthError{Description: safewErrorDescription(respBody)}
	}
	if resp.StatusCode >= 400 {
		desc := safewErrorDescription(respBody)
		if desc != "" {
			return nil, offset, fmt.Errorf("safew getUpdates status %d: %s", resp.StatusCode, desc)
		}
		return nil, offset, fmt.Errorf("safew getUpdates status %d", resp.StatusCode)
	}
	var api safewAPIResponse
	if err := json.Unmarshal(respBody, &api); err == nil && !api.OK {
		if resp.StatusCode == 401 || strings.Contains(strings.ToLower(api.Description), "token") {
			return nil, offset, &SafewAuthError{Description: api.Description}
		}
		return nil, offset, fmt.Errorf("safew: %s", api.Description)
	}
	chats, maxID, err := GroupsFromUpdates(respBody)
	if err != nil {
		return nil, offset, err
	}
	next := offset
	if maxID > 0 {
		next = maxID + 1
	}
	return chats, next, nil
}

func parseSafewChatID(raw json.RawMessage) (string, error) {
	raw = bytes.TrimSpace(raw)
	if len(raw) == 0 || string(raw) == "null" {
		return "", fmt.Errorf("safew: chat_id is required")
	}
	if raw[0] == '"' {
		var id string
		if err := json.Unmarshal(raw, &id); err != nil {
			return "", fmt.Errorf("safew: invalid chat_id: %w", err)
		}
		id = strings.TrimSpace(id)
		if id == "" {
			return "", fmt.Errorf("safew: chat_id is required")
		}
		return id, nil
	}
	return string(raw), nil
}

func safewErrorDescription(body []byte) string {
	var api safewAPIResponse
	if err := json.Unmarshal(body, &api); err != nil {
		return strings.TrimSpace(string(body))
	}
	switch {
	case api.Description != "" && api.ErrorMsg != "":
		return api.Description + ": " + api.ErrorMsg
	case api.ErrorMsg != "":
		return api.ErrorMsg
	default:
		return api.Description
	}
}

func escapeMarkdownV2(s string) string {
	var b strings.Builder
	b.Grow(len(s))
	for _, r := range s {
		switch r {
		case '_', '*', '[', ']', '(', ')', '~', '`', '>', '#', '+', '-', '=', '|', '{', '}', '.', '!', '\\':
			b.WriteByte('\\')
		}
		b.WriteRune(r)
	}
	return b.String()
}

type SafewChat struct {
	ID       string  `json:"id"`
	Type     string  `json:"type"`
	Title    string  `json:"title"`
	Username *string `json:"username"`
}

func GroupsFromUpdates(body []byte) ([]SafewChat, int64, error) {
	dec := json.NewDecoder(bytes.NewReader(body))
	dec.UseNumber()
	var wrap struct {
		OK     bool              `json:"ok"`
		Result []json.RawMessage `json:"result"`
	}
	if err := dec.Decode(&wrap); err != nil {
		return nil, 0, fmt.Errorf("safew updates decode: %w", err)
	}
	seen := map[string]SafewChat{}
	var maxID int64
	for _, item := range wrap.Result {
		id, chat, err := parseUpdateItem(item)
		if err != nil {
			return nil, 0, err
		}
		if id > maxID {
			maxID = id
		}
		if chat == nil {
			continue
		}
		if chat.Type != "group" && chat.Type != "supergroup" {
			continue
		}
		seen[chat.ID] = *chat
	}
	out := make([]SafewChat, 0, len(seen))
	for _, c := range seen {
		out = append(out, c)
	}
	return out, maxID, nil
}

func parseUpdateItem(item json.RawMessage) (int64, *SafewChat, error) {
	dec := json.NewDecoder(bytes.NewReader(item))
	dec.UseNumber()
	var u map[string]json.RawMessage
	if err := dec.Decode(&u); err != nil {
		return 0, nil, err
	}
	var updateID int64
	if raw, ok := u["update_id"]; ok {
		var n json.Number
		if err := json.Unmarshal(raw, &n); err == nil {
			updateID, _ = n.Int64()
		}
	}
	for _, key := range []string{"message", "edited_message", "channel_post", "edited_channel_post", "my_chat_member", "chat_member"} {
		raw, ok := u[key]
		if !ok {
			continue
		}
		chat := chatFromNested(raw)
		if chat != nil {
			return updateID, chat, nil
		}
	}
	return updateID, nil, nil
}

func chatFromNested(raw json.RawMessage) *SafewChat {
	dec := json.NewDecoder(bytes.NewReader(raw))
	dec.UseNumber()
	var obj map[string]json.RawMessage
	if err := dec.Decode(&obj); err != nil {
		return nil
	}
	chatRaw, ok := obj["chat"]
	if !ok {
		return nil
	}
	dec = json.NewDecoder(bytes.NewReader(chatRaw))
	dec.UseNumber()
	var c struct {
		ID       json.Number `json:"id"`
		Type     string      `json:"type"`
		Title    string      `json:"title"`
		Username *string     `json:"username"`
	}
	if err := dec.Decode(&c); err != nil {
		return nil
	}
	id := strings.TrimSpace(c.ID.String())
	if id == "" {
		return nil
	}
	return &SafewChat{ID: id, Type: c.Type, Title: c.Title, Username: c.Username}
}

func FilterSafewChats(chats []SafewChat, q string) []SafewChat {
	q = strings.TrimSpace(strings.ToLower(q))
	if q == "" {
		return chats
	}
	var out []SafewChat
	for _, c := range chats {
		uname := ""
		if c.Username != nil {
			uname = *c.Username
		}
		if strings.Contains(strings.ToLower(c.Title), q) ||
			strings.Contains(strings.ToLower(uname), q) ||
			strings.Contains(strings.ToLower(c.ID), q) {
			out = append(out, c)
		}
	}
	return out
}