package help

import (
	"io"
	"net/http"
	"strings"
	"testing"
	"unicode/utf8"

	"github.com/bwmarrin/discordgo"
)

// Discord refuses an embed that is over its limits, and then /help would send
// nothing. This catches it when a command is added to the text.
func TestHelpFitsDiscordsLimits(t *testing.T) {
	list := embeds(&discordgo.MessageEmbedAuthor{Name: "Velox Bot"})
	if len(list) == 0 {
		t.Fatal("no help")
	}
	seen := 0
	for n, e := range list {
		total := utf8.RuneCountInString(e.Title) + utf8.RuneCountInString(e.Description)
		if len(e.Fields) > 25 {
			t.Errorf("embed %d has %d fields, at most 25", n, len(e.Fields))
		}
		for _, f := range e.Fields {
			seen++
			if l := utf8.RuneCountInString(f.Value); l == 0 || l > maxFieldChars {
				t.Errorf("field %q has %d characters, must be 1 to %d", f.Name, l, maxFieldChars)
			}
			if l := utf8.RuneCountInString(f.Name); l == 0 || l > 256 {
				t.Errorf("field name %q has %d characters, at most 256", f.Name, l)
			}
			total += fieldSize(f)
		}
		if total > 6000 {
			t.Errorf("embed %d has %d characters, Discord allows 6000", n, total)
		}
	}
	if seen != len(fields()) {
		t.Errorf("%d fields shown of %d", seen, len(fields()))
	}
}

// fakeDiscord answers the calls /help makes and records what the member was
// shown. dm decides whether the direct message works.
type fakeDiscord struct {
	dm        bool
	edited    []byte
	callbacks int
	sent      int
}

func (f *fakeDiscord) RoundTrip(r *http.Request) (*http.Response, error) {
	reply := func(code int, body string) (*http.Response, error) {
		return &http.Response{StatusCode: code, Body: io.NopCloser(strings.NewReader(body)), Header: http.Header{"Content-Type": {"application/json"}}, Request: r}, nil
	}
	switch {
	case strings.HasSuffix(r.URL.Path, "/callback"):
		f.callbacks++
		return reply(204, "")
	case strings.HasSuffix(r.URL.Path, "/users/@me/channels"):
		if !f.dm {
			return reply(403, `{"message":"Cannot send messages to this user","code":50007}`)
		}
		return reply(200, `{"id":"900","type":1}`)
	case strings.Contains(r.URL.Path, "/channels/900/messages"):
		f.sent++
		return reply(200, `{"id":"1"}`)
	case strings.Contains(r.URL.Path, "/messages/@original"):
		f.edited, _ = io.ReadAll(r.Body)
		return reply(200, `{"id":"2"}`)
	}
	return reply(404, `{"message":"unexpected `+r.URL.Path+`"}`)
}

func run(t *testing.T, f *fakeDiscord, guild string) {
	t.Helper()
	s, err := discordgo.New("Bot x")
	if err != nil {
		t.Fatal(err)
	}
	s.Client = &http.Client{Transport: f}
	s.MaxRestRetries = 0
	i := &discordgo.InteractionCreate{Interaction: &discordgo.Interaction{
		ID: "1", Token: "tok", AppID: "100", GuildID: guild,
		Member: &discordgo.Member{User: &discordgo.User{ID: "42"}},
	}}
	HelpHandler(s, i)
}

func TestHelpGoesToDMs(t *testing.T) {
	f := &fakeDiscord{dm: true}
	run(t, f, "5")
	if f.sent == 0 || !strings.Contains(string(f.edited), "Check your DMs") || strings.Contains(string(f.edited), `"embeds"`) {
		t.Errorf("sent=%d edited=%s", f.sent, f.edited)
	}
}

func TestHelpFallsBackToTheChannelWhenDMsAreOff(t *testing.T) {
	f := &fakeDiscord{dm: false}
	run(t, f, "5")
	got := string(f.edited)
	if f.sent != 0 || !strings.Contains(got, "couldn't DM you") || !strings.Contains(got, `"embeds"`) || !strings.Contains(got, "Velox Bot Help") {
		t.Errorf("the help should be shown in the reply: sent=%d edited=%s", f.sent, got)
	}
}

func TestHelpInADMIsShownDirectly(t *testing.T) {
	f := &fakeDiscord{dm: true}
	run(t, f, "")
	if f.callbacks != 1 || f.sent != 0 || f.edited != nil {
		t.Errorf("one direct answer, no DM: %+v", f)
	}
}

// The help is meant to be wide and short: inline fields, so Discord puts
// three side by side, and it should fit in one message.
func TestHelpIsCompactAndInline(t *testing.T) {
	if n := len(embeds(&discordgo.MessageEmbedAuthor{Name: "Velox Bot"})); n != 1 {
		t.Errorf("the help should fit in one message, it takes %d", n)
	}
	inline := 0
	for _, f := range fields() {
		if f.Inline {
			inline++
		}
	}
	if inline < len(fields())-2 {
		t.Errorf("only %d of %d fields are inline", inline, len(fields()))
	}
}