package laniakea

import (
	"errors"
	"strings"
	"testing"

	"git.scuroneko.dev/scuroneko/laniakea/tgapi"
	"git.scuroneko.dev/scuroneko/sneklog/v2"
)

type sequenceDraftIDGenerator struct {
	ids []uint64
	pos int
}

func (g *sequenceDraftIDGenerator) Next() uint64 {
	id := g.ids[g.pos]
	g.pos++
	return id
}

func TestDraftFlushRequiresChatID(t *testing.T) {
	draft := NewRandomDraftProvider(&tgapi.API{}).NewDraft(tgapi.ParseNone)
	draft.Message = "hello"

	if err := draft.Flush(); !errors.Is(err, ErrDraftChatIDZero) {
		t.Fatalf("expected ErrDraftChatIDZero, got %v", err)
	}
}

func TestDraftFlushEmptyRemovesDraft(t *testing.T) {
	provider := NewLinearDraftProvider(nil, 0)
	draft := provider.NewDraft(tgapi.ParseNone)

	if err := draft.Flush(); err != nil {
		t.Fatalf("Flush returned error: %v", err)
	}
	if _, ok := provider.GetDraft(draft.ID); ok {
		t.Fatal("empty flushed draft remained in provider")
	}
}

func TestDraftFlushAllRemovesClearedDrafts(t *testing.T) {
	provider := NewLinearDraftProvider(nil, 0)
	draft := provider.NewDraft(tgapi.ParseNone)
	draft.Message = "discarded"
	draft.Clear()

	if err := provider.FlushAll(); err != nil {
		t.Fatalf("FlushAll returned error: %v", err)
	}
	if _, ok := provider.GetDraft(draft.ID); ok {
		t.Fatal("cleared draft remained in provider")
	}
}

func TestMsgContextNewDraftWorksWithoutLimiter(t *testing.T) {
	ctx := &MessageContext{
		API: &tgapi.API{},
		Msg: &tgapi.Message{
			Chat: &tgapi.Chat{ID: 42, Type: tgapi.ChatTypePrivate},
		},
		Logger:        sneklog.NewLogger(),
		draftProvider: NewRandomDraftProvider(&tgapi.API{}),
	}

	draft := ctx.NewDraft()
	if draft == nil {
		t.Fatal("expected draft")
		return
	}
	if draft.chatID != 42 {
		t.Fatalf("unexpected chat id: %d", draft.chatID)
	}
}

func TestDraftProviderSkipsZeroAndCollidingIDs(t *testing.T) {
	provider := &DraftProvider{
		api:       &tgapi.API{},
		drafts:    make(map[uint64]*Draft),
		generator: &sequenceDraftIDGenerator{ids: []uint64{0, 7, 7, 8}},
	}

	first := provider.NewDraft(tgapi.ParseNone)
	second := provider.NewDraft(tgapi.ParseNone)
	if first.ID != 7 || second.ID != 8 {
		t.Fatalf("unexpected draft IDs: first=%d second=%d", first.ID, second.ID)
	}
	if got := len(provider.drafts); got != 2 {
		t.Fatalf("collision overwrote a draft: got %d drafts", got)
	}
}

func TestDraftReturnsErrorWhenAPIIsNil(t *testing.T) {
	draft := NewLinearDraftProvider(nil, 0).NewDraft(tgapi.ParseNone).SetChat(42, 0)
	if err := draft.Push("hello"); !errors.Is(err, ErrAPIIsNil) {
		t.Fatalf("expected ErrAPIIsNil from Push, got %v", err)
	}
	draft.Message = "hello"
	if err := draft.Flush(); !errors.Is(err, ErrAPIIsNil) {
		t.Fatalf("expected ErrAPIIsNil from Flush, got %v", err)
	}
}

func TestDraftFlushRejectsLongMessage(t *testing.T) {
	draft := NewRandomDraftProvider(&tgapi.API{}).NewDraft(tgapi.ParseNone).SetChat(42, 0)
	draft.Message = strings.Repeat("a", maxMessageTextLen+1)

	if err := draft.Flush(); !errors.Is(err, ErrMessageTooLong) {
		t.Fatalf("expected ErrMessageTooLong, got %v", err)
	}
}

func TestDraftPushRejectsLongMessage(t *testing.T) {
	draft := NewRandomDraftProvider(&tgapi.API{}).NewDraft(tgapi.ParseNone).SetChat(42, 0)

	if err := draft.Push(strings.Repeat("a", maxMessageTextLen+1)); !errors.Is(err, ErrMessageTooLong) {
		t.Fatalf("expected ErrMessageTooLong, got %v", err)
	}
}

// TestDraftPushLeavesMessageUnchangedOnValidationFailure covers the validation
// order fix: when the candidate Message (current + new text) overflows the
// Telegram limit, the existing Message must remain intact so callers can
// recover and retry with a shorter payload instead of finding the draft in
// a half-mutated state.
func TestDraftPushLeavesMessageUnchangedOnValidationFailure(t *testing.T) {
	draft := NewRandomDraftProvider(&tgapi.API{}).NewDraft(tgapi.ParseNone).SetChat(42, 0)
	draft.Message = "hello"

	if err := draft.Push(strings.Repeat("a", maxMessageTextLen+1)); !errors.Is(err, ErrMessageTooLong) {
		t.Fatalf("expected ErrMessageTooLong, got %v", err)
	}
	if draft.Message != "hello" {
		t.Fatalf("expected draft Message to stay %q, got %q", "hello", draft.Message)
	}
}