package main

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/http/httptest"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/stretchr/testify/require"
)

const (
	// telegramTestToken is the bot token of the tests. It has the form of a
	// real token.
	telegramTestToken = "123456:TEST-secret_token"

	// telegramTestOwner is the user ID of the owner of the test bot.
	telegramTestOwner = 4242
)

func TestGetUpdatesAsksForMessagesFromTheOffset(t *testing.T) {
	server := newTelegramFake(t)
	server.Add(TelegramUpdate{
		UpdateID: 7,
		Message:  telegramOwnerMessage("hello"),
	})

	updates, err := newTelegramAPI(server.URL, telegramTestToken).GetUpdates(t.Context(), 7)
	require.NoError(t, err)
	require.Len(t, updates, 1)
	require.Equal(t, int64(7), updates[0].UpdateID)
	require.Equal(t, "hello", updates[0].Message.Text)

	call := server.Calls()[0]
	require.Equal(t, "getUpdates", call.method)
	require.Equal(t, map[string]any{
		"offset":          float64(7),
		"timeout":         float64(telegramPollSeconds),
		"allowed_updates": []any{"message"},
	}, call.params)
}

func TestSendMessageSendsPlainText(t *testing.T) {
	server := newTelegramFake(t)
	err := newTelegramAPI(server.URL, telegramTestToken).SendMessage(t.Context(), telegramTestOwner, "*not bold*", nil)
	require.NoError(t, err)

	require.Equal(t, map[string]any{
		"chat_id": float64(telegramTestOwner),
		"text":    "*not bold*",
	}, server.Calls()[0].params)
}

func TestSendMessageSendsTheEntities(t *testing.T) {
	server := newTelegramFake(t)
	err := newTelegramAPI(server.URL, telegramTestToken).SendMessage(t.Context(), telegramTestOwner, "a link", []TelegramEntity{
		{
			Type:   "text_link",
			Offset: 2,
			Length: 4,
			URL:    "https://example.com",
		},
	})
	require.NoError(t, err)

	require.Equal(t, []any{
		map[string]any{
			"type":   "text_link",
			"offset": float64(2),
			"length": float64(4),
			"url":    "https://example.com",
		},
	}, server.Calls()[0].params["entities"])
}

func TestSendRichMessageSendsTheMarkdownUnchanged(t *testing.T) {
	server := newTelegramFake(t)
	markdown := "| a | b |\n|---|---|\n| **1** | `2` |"
	err := newTelegramAPI(server.URL, telegramTestToken).SendRichMessage(t.Context(), telegramTestOwner, markdown)
	require.NoError(t, err)

	call := server.Calls()[0]
	require.Equal(t, "sendRichMessage", call.method)
	require.Equal(t, map[string]any{
		"chat_id": float64(telegramTestOwner),
		"rich_message": map[string]any{
			"markdown": markdown,
		},
	}, call.params)
}

func TestSendCallsTimeOutOnAStalledConnection(t *testing.T) {
	testCases := []struct {
		method string
		send   func(ctx context.Context, api *TelegramAPI) error
	}{
		{
			method: "sendMessage",
			send: func(ctx context.Context, api *TelegramAPI) error {
				return api.SendMessage(ctx, telegramTestOwner, "hi", nil)
			},
		},
		{
			method: "sendRichMessage",
			send: func(ctx context.Context, api *TelegramAPI) error {
				return api.SendRichMessage(ctx, telegramTestOwner, "hi")
			},
		},
	}

	for _, tc := range testCases {
		t.Run(tc.method, func(t *testing.T) {
			server := newTelegramFake(t)
			server.stall = func(call TelegramFakeCall) bool {
				return call.method == tc.method
			}

			api := newTelegramAPI(server.URL, telegramTestToken)
			api.sendTimeout = 50 * time.Millisecond
			start := time.Now()
			err := tc.send(t.Context(), api)
			require.ErrorIs(t, err, errTelegramNetwork)
			require.Less(t, time.Since(start), 5*time.Second)
			require.NotContains(t, err.Error(), telegramTestToken)
			require.NotContains(t, err.Error(), server.URL)

			retry, _ := telegramRetryable(err)
			require.True(t, retry)

			api.sendTimeout = time.Hour
			ctx, cancel := context.WithCancel(t.Context())
			time.AfterFunc(50*time.Millisecond, cancel)
			start = time.Now()
			err = tc.send(ctx, api)
			require.Error(t, err)
			require.Less(t, time.Since(start), 5*time.Second)
		})
	}
}

func TestBotErrorsDoNotHoldTheToken(t *testing.T) {
	testCases := []struct {
		name      string
		reply     func(w http.ResponseWriter)
		retry     bool
		wait      time.Duration
		rejected  bool
		errorText string
	}{
		{
			name: "refused connection is retried",
			reply: func(w http.ResponseWriter) {
				conn, _, err := http.NewResponseController(w).Hijack()
				if err == nil {
					_ = conn.Close()
				}
			},
			retry:     true,
			errorText: "no valid answer",
		},
		{
			name: "rate limit waits as asked",
			reply: func(w http.ResponseWriter) {
				w.WriteHeader(http.StatusTooManyRequests)
				_, _ = io.WriteString(w, `{"ok":false,"error_code":429,"description":"Too Many Requests: retry after 3","parameters":{"retry_after":3}}`)
			},
			retry:     true,
			wait:      3 * time.Second,
			errorText: "answered 429",
		},
		{
			name: "server error page is retried",
			reply: func(w http.ResponseWriter) {
				w.WriteHeader(http.StatusBadGateway)
				_, _ = io.WriteString(w, "<html>bad gateway</html>")
			},
			retry:     true,
			errorText: "answered 502: Bad Gateway",
		},
		{
			name: "token echoed in a description is hidden",
			reply: func(w http.ResponseWriter) {
				w.WriteHeader(http.StatusUnauthorized)
				_, _ = io.WriteString(w, `{"ok":false,"error_code":401,"description":"Unauthorized: bot`+telegramTestToken+`"}`)
			},
			retry:     false,
			errorText: "Unauthorized: botTOKEN",
		},
		{
			name: "bad request is a refusal",
			reply: func(w http.ResponseWriter) {
				w.WriteHeader(http.StatusBadRequest)
				_, _ = io.WriteString(w, `{"ok":false,"error_code":400,"description":"Bad Request: can't parse"}`)
			},
			retry:     false,
			rejected:  true,
			errorText: "answered 400: Bad Request: can't parse",
		},
		{
			name: "unknown method is a refusal",
			reply: func(w http.ResponseWriter) {
				w.WriteHeader(http.StatusNotFound)
				_, _ = io.WriteString(w, `{"ok":false,"error_code":404,"description":"Not Found"}`)
			},
			retry:     false,
			rejected:  true,
			errorText: "answered 404: Not Found",
		},
		{
			name: "not found page of a proxy is not a refusal",
			reply: func(w http.ResponseWriter) {
				w.WriteHeader(http.StatusNotFound)
				_, _ = io.WriteString(w, "<html>not found</html>")
			},
			retry:     false,
			errorText: "answered 404: Not Found",
		},
		{
			name: "broken answer is retried",
			reply: func(w http.ResponseWriter) {
				_, _ = io.WriteString(w, `{"ok":`)
			},
			retry:     true,
			errorText: "decode answer",
		},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
				tc.reply(w)
			}))
			t.Cleanup(server.Close)

			err := newTelegramAPI(server.URL, telegramTestToken).SendMessage(t.Context(), telegramTestOwner, "hi", nil)
			require.ErrorContains(t, err, tc.errorText)
			require.NotContains(t, err.Error(), telegramTestToken)
			require.NotContains(t, err.Error(), server.URL)

			retry, wait := telegramRetryable(err)
			require.Equal(t, tc.retry, retry)
			require.Equal(t, tc.wait, wait)
			require.Equal(t, tc.rejected, telegramRejected(err))
		})
	}

	server := httptest.NewServer(http.NotFoundHandler())
	server.Close()

	_, err := newTelegramAPI(server.URL, telegramTestToken).GetUpdates(t.Context(), 0)
	require.ErrorIs(t, err, errTelegramNetwork)
	require.NotContains(t, err.Error(), telegramTestToken)
}

// TelegramFakeCall is one call of the fake Bot API. OK tells if the call got a
// success answer.
type TelegramFakeCall struct {
	method string
	params map[string]any
	ok     bool
}

// TelegramFake is a fake Bot API server for telegramTestToken. getUpdates
// returns the added updates from the offset on, or waits a short time when
// there are none. The other methods succeed, unless fail gives an error answer
// for a call. An answer with HTTP 429 asks for a wait of one second. When stall
// is true for a call, the call gets no answer until the client gives it up or
// the test ends. Fail and stall run with the mutex held.
type TelegramFake struct {
	*httptest.Server

	mutex   sync.Mutex
	updates []TelegramUpdate
	calls   []TelegramFakeCall
	fail    func(call TelegramFakeCall) (int, string)
	stall   func(call TelegramFakeCall) bool
	added   chan struct{}
	stopped chan struct{}
}

// Add makes update available to getUpdates.
func (f *TelegramFake) Add(update TelegramUpdate) {
	f.mutex.Lock()
	f.updates = append(f.updates, update)
	f.mutex.Unlock()

	select {
	case f.added <- struct{}{}:
	default:
	}
}

// Calls returns the calls so far.
func (f *TelegramFake) Calls() []TelegramFakeCall {
	f.mutex.Lock()
	defer f.mutex.Unlock()

	return append([]TelegramFakeCall(nil), f.calls...)
}

// Sent returns the texts of the sendMessage calls and the Markdown of the
// sendRichMessage calls that succeeded, in order.
func (f *TelegramFake) Sent() []string {
	var texts []string
	for _, call := range f.Calls() {
		switch {
		case !call.ok:
		case call.method == "sendMessage":
			texts = append(texts, call.params["text"].(string))
		case call.method == "sendRichMessage":
			texts = append(texts, call.params["rich_message"].(map[string]any)["markdown"].(string))
		}
	}

	return texts
}

func (f *TelegramFake) serve(w http.ResponseWriter, r *http.Request) {
	method, found := strings.CutPrefix(r.URL.Path, "/bot"+telegramTestToken+"/")
	if !found {
		http.Error(w, `{"ok":false,"error_code":404,"description":"Not Found"}`, http.StatusNotFound)
		return
	}

	var params map[string]any
	err := json.NewDecoder(r.Body).Decode(&params)
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	}

	call := TelegramFakeCall{
		method: method,
		params: params,
	}

	f.mutex.Lock()
	status, description := 0, ""
	if f.fail != nil {
		status, description = f.fail(call)
	}

	stall := f.stall != nil && f.stall(call)
	f.mutex.Unlock()

	if stall {
		f.record(call)
		select {
		case <-r.Context().Done():
		case <-f.stopped:
		}

		return
	}

	if status != 0 {
		f.record(call)
		w.WriteHeader(status)
		wait := 0
		if status == http.StatusTooManyRequests {
			wait = 1
		}

		_, _ = fmt.Fprintf(w, `{"ok":false,"error_code":%d,"description":%q,"parameters":{"retry_after":%d}}`, status, description, wait)

		return
	}

	call.ok = true
	f.record(call)
	if method != "getUpdates" {
		_, _ = io.WriteString(w, `{"ok":true,"result":true}`)
		return
	}

	offset := int64(params["offset"].(float64))
	updates := f.from(offset)
	if len(updates) == 0 {
		select {
		case <-f.added:
		case <-time.After(50 * time.Millisecond):
		case <-r.Context().Done():
		}

		updates = f.from(offset)
	}

	_ = json.NewEncoder(w).Encode(map[string]any{
		"ok":     true,
		"result": updates,
	})
}

// record keeps call.
func (f *TelegramFake) record(call TelegramFakeCall) {
	f.mutex.Lock()
	defer f.mutex.Unlock()

	f.calls = append(f.calls, call)
}

// from returns the updates from offset on, and forgets the ones before it, as
// Telegram does.
func (f *TelegramFake) from(offset int64) []TelegramUpdate {
	f.mutex.Lock()
	defer f.mutex.Unlock()

	var updates []TelegramUpdate
	kept := f.updates[:0]
	for _, update := range f.updates {
		if update.UpdateID >= offset {
			updates = append(updates, update)
			kept = append(kept, update)
		}
	}

	f.updates = kept

	return updates
}

// newTelegramFake starts a fake Bot API server that stops at the end of the
// test.
func newTelegramFake(t *testing.T) *TelegramFake {
	t.Helper()

	f := &TelegramFake{
		added:   make(chan struct{}, 1),
		stopped: make(chan struct{}),
	}

	f.Server = httptest.NewServer(http.HandlerFunc(f.serve))
	t.Cleanup(f.Close)
	t.Cleanup(func() {
		close(f.stopped)
	})

	return f
}

// telegramOwnerMessage returns a text message of the owner in the private chat.
func telegramOwnerMessage(text string) *TelegramMessage {
	return &TelegramMessage{
		Chat: TelegramChat{
			ID:   telegramTestOwner,
			Type: "private",
		},
		From: &TelegramUser{
			ID: telegramTestOwner,
		},
		Text: text,
	}
}