package main

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

const telegramAPIBase = "https://api.telegram.org"

type TelegramClient struct {
	httpClient *http.Client
	apiBase    string
}

func NewTelegramClient() *TelegramClient {
	return &TelegramClient{
		httpClient: &http.Client{Timeout: 10 * time.Second},
		apiBase:    telegramAPIBase,
	}
}

type SendMessageParams struct {
	ChatID int64  `json:"chat_id"`
	Text   string `json:"text"`
}

type apiResponse struct {
	OK          bool            `json:"ok"`
	Description string          `json:"description,omitempty"`
	Result      json.RawMessage `json:"result,omitempty"`
	ErrorCode   int             `json:"error_code,omitempty"`
}

func (c *TelegramClient) SendMessage(ctx context.Context, token string, params SendMessageParams) error {
	body, err := json.Marshal(params)
	if err != nil {
		return err
	}
	endpoint := fmt.Sprintf("%s/bot%s/sendMessage", c.apiBase, token)
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint, bytes.NewReader(body))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	respBody, _ := io.ReadAll(resp.Body)

	var ar apiResponse
	if jerr := json.Unmarshal(respBody, &ar); jerr != nil {
		return fmt.Errorf("decode telegram response (status %d): %w", resp.StatusCode, jerr)
	}
	if !ar.OK {
		return fmt.Errorf("telegram api error (code=%d): %s", ar.ErrorCode, ar.Description)
	}
	return nil
}

type SetWebhookParams struct {
	URL                string   `json:"url"`
	SecretToken        string   `json:"secret_token,omitempty"`
	DropPendingUpdates bool     `json:"drop_pending_updates,omitempty"`
	AllowedUpdates     []string `json:"allowed_updates,omitempty"`
	MaxConnections     int      `json:"max_connections,omitempty"`
}

func (c *TelegramClient) SetWebhook(ctx context.Context, token string, params SetWebhookParams) error {
	body, err := json.Marshal(params)
	if err != nil {
		return err
	}
	endpoint := fmt.Sprintf("%s/bot%s/setWebhook", c.apiBase, token)
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint, bytes.NewReader(body))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	respBody, _ := io.ReadAll(resp.Body)

	var ar apiResponse
	if jerr := json.Unmarshal(respBody, &ar); jerr != nil {
		return fmt.Errorf("decode telegram response (status %d): %w", resp.StatusCode, jerr)
	}
	if !ar.OK {
		return fmt.Errorf("telegram setWebhook error (code=%d): %s", ar.ErrorCode, ar.Description)
	}
	return nil
}

func (c *TelegramClient) DeleteWebhook(ctx context.Context, token string) error {
	endpoint := fmt.Sprintf("%s/bot%s/deleteWebhook", c.apiBase, token)
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint, nil)
	if err != nil {
		return err
	}

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	respBody, _ := io.ReadAll(resp.Body)

	var ar apiResponse
	if jerr := json.Unmarshal(respBody, &ar); jerr != nil {
		return fmt.Errorf("decode telegram response (status %d): %w", resp.StatusCode, jerr)
	}
	if !ar.OK {
		return fmt.Errorf("telegram deleteWebhook error (code=%d): %s", ar.ErrorCode, ar.Description)
	}
	return nil
}

type WebhookInfo struct {
	URL                string `json:"url"`
	HasCustomCert      bool   `json:"has_custom_certificate"`
	PendingUpdateCount int    `json:"pending_update_count"`
	LastErrorDate      int64  `json:"last_error_date,omitempty"`
	LastErrorMessage   string `json:"last_error_message,omitempty"`
}

func (c *TelegramClient) GetWebhookInfo(ctx context.Context, token string) (*WebhookInfo, error) {
	endpoint := fmt.Sprintf("%s/bot%s/getWebhookInfo", c.apiBase, token)
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return nil, err
	}
	resp, err := c.httpClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	respBody, _ := io.ReadAll(resp.Body)

	var ar apiResponse
	if jerr := json.Unmarshal(respBody, &ar); jerr != nil {
		return nil, fmt.Errorf("decode telegram response: %w", jerr)
	}
	if !ar.OK {
		return nil, fmt.Errorf("telegram getWebhookInfo error: %s", ar.Description)
	}
	var info WebhookInfo
	if jerr := json.Unmarshal(ar.Result, &info); jerr != nil {
		return nil, fmt.Errorf("decode webhook info: %w", jerr)
	}
	return &info, nil
}

// botBuildURL is exposed for tests; not used directly.
var _ = url.Parse