package chatd

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"regexp"
	"slices"
	"strings"
	"time"
	"unicode"

	"charm.land/fantasy"
	"charm.land/fantasy/object"
	fantasyanthropic "charm.land/fantasy/providers/anthropic"
	fantasyazure "charm.land/fantasy/providers/azure"
	fantasybedrock "charm.land/fantasy/providers/bedrock"
	fantasygoogle "charm.land/fantasy/providers/google"
	fantasyopenai "charm.land/fantasy/providers/openai"
	fantasyopenrouter "charm.land/fantasy/providers/openrouter"
	fantasyvercel "charm.land/fantasy/providers/vercel"
	"github.com/google/uuid"
	"golang.org/x/xerrors"

	"cdr.dev/slog/v3"
	"github.com/coder/coder/v2/coderd/database"
	"github.com/coder/coder/v2/coderd/util/ptr"
	"github.com/coder/coder/v2/coderd/x/chatd/chatdebug"
	"github.com/coder/coder/v2/coderd/x/chatd/chatprompt"
	"github.com/coder/coder/v2/coderd/x/chatd/chatprovider"
	"github.com/coder/coder/v2/coderd/x/chatd/chatretry"
	"github.com/coder/coder/v2/codersdk"
)

const titleGenerationPrompt = "Write a short title for the user's message. " +
	"Populate the title field with the result. " +
	"Return only the title text in 2-8 words. " +
	"Do not answer the user or describe the title-writing task. " +
	"Preserve specific identifiers such as PR numbers, repo names, file paths, function names, and error messages. " +
	"If the message is short or vague, stay close to the user's wording instead of inventing context. " +
	"Write the title in the same language as the user's message. " +
	"Sentence case. No quotes, emoji, markdown, or trailing punctuation.\n\n" +
	"Examples:\n" +
	"Message: how do I set up SSO with Okta?\n" +
	"Title: Set up SSO with Okta\n\n" +
	"Message: getting `pq: duplicate key value violates unique constraint` when running migrations in coderd\n" +
	"Title: Fix pq duplicate key violation in coderd migrations\n\n" +
	"Message: review PR #123 in acme/webapp and flag risky changes\n" +
	"Title: Review risky changes in acme/webapp PR #123\n\n" +
	"Message: corrige el error de compilación en main.go\n" +
	"Title: Corregir error de compilación en main.go\n\n" +
	"Message: help\n" +
	"Title: Help request"

// quickgenTemperature keeps title and status-label output stable
// across repeated runs over the same input. Fantasy providers drop
// this with a call warning for models that reject it (OpenAI
// reasoning models, Anthropic thinking models), but only for model
// names they recognize. generateQuickgenObject handles models that
// reject the parameter at the API instead.
const quickgenTemperature = 0.0

// generateQuickgenObject generates a structured object with provider
// retries and the pinned quickgen temperature. Model aliases served
// through gateways such as AI Bridge are not recognized by fantasy's
// per-model parameter stripping and can reject temperature with a
// bad-request error, so the call is retried without temperature when
// the model rejects it.
func generateQuickgenObject[T any](
	ctx context.Context,
	model fantasy.LanguageModel,
	call fantasy.ObjectCall,
) (*fantasy.ObjectResult[T], error) {
	call.Temperature = ptr.Ref(quickgenTemperature)
	var result *fantasy.ObjectResult[T]
	err := chatretry.Retry(ctx, func(retryCtx context.Context) error {
		var genErr error
		result, genErr = object.Generate[T](retryCtx, model, call)
		if call.Temperature != nil && isTemperatureRejectedError(genErr) {
			// The model rejects the temperature parameter. Drop it
			// for this and any later retry attempts.
			call.Temperature = nil
			result, genErr = object.Generate[T](retryCtx, model, call)
		}
		return genErr
	}, nil)
	return result, err
}

// isTemperatureRejectedError reports whether a provider rejected the
// request because the model does not accept the temperature parameter,
// for example Anthropic's "`temperature` is deprecated for this model."
// or OpenAI's "Unsupported parameter: 'temperature' is not supported
// with this model.". Quickgen only sends a valid temperature value, so
// any bad-request response mentioning temperature means the model
// rejects the parameter itself.
func isTemperatureRejectedError(err error) bool {
	var providerErr *fantasy.ProviderError
	if !errors.As(err, &providerErr) {
		return false
	}
	if providerErr.StatusCode != http.StatusBadRequest {
		return false
	}
	text := strings.ToLower(providerErr.Error() + " " + string(providerErr.ResponseBody))
	return strings.Contains(text, "temperature")
}

const (
	// maxConversationContextRunes caps the conversation sample in manual
	// title prompts to avoid exceeding model context windows.
	maxConversationContextRunes = 6000
	// maxLatestUserMessageRunes caps the latest user message excerpt.
	maxLatestUserMessageRunes = 1000
	// recentTurnWindow is the number of most recent turns included
	// alongside the first user turn in manual title context.
	recentTurnWindow = 3
)

// preferredTitleModels are lightweight models used for title
// generation, one per provider type. Each entry uses the
// cheapest/fastest small model for that provider as identified
// by the charmbracelet/catwalk model catalog. Providers that
// aren't configured (no API key) are silently skipped.
var preferredTitleModels = []struct {
	provider string
	model    string
}{
	{fantasyanthropic.Name, "claude-haiku-4-5"},
	{fantasyopenai.Name, "gpt-4o-mini"},
	{fantasygoogle.Name, "gemini-2.5-flash"},
	{fantasyazure.Name, "gpt-4o-mini"},
	{fantasybedrock.Name, "global.anthropic.claude-haiku-4-5-20251001-v1:0"},
	{fantasyopenrouter.Name, "anthropic/claude-3.5-haiku"},
	{fantasyvercel.Name, "anthropic/claude-haiku-4.5"},
}

// Debug attribution uses configured identities for title calls and the
// resolved identity for status-label calls.
type shortTextCandidate struct {
	provider string
	model    string
	resolved resolvedModelCall
}

func selectPreferredConfiguredShortTextModelConfig(
	configs []database.GetEnabledChatModelConfigsByOrganizationRow,
) (database.ChatModelConfig, bool) {
	for _, preferred := range preferredTitleModels {
		for _, config := range configs {
			if chatprovider.NormalizeProvider(config.Provider) != preferred.provider {
				continue
			}
			if !strings.EqualFold(strings.TrimSpace(config.ChatModelConfig.Model), preferred.model) {
				continue
			}
			return config.ChatModelConfig, true
		}
	}
	return database.ChatModelConfig{}, false
}

func normalizeShortTextOutput(text string) string {
	text = strings.TrimSpace(text)
	if text == "" {
		return ""
	}

	text = strings.Trim(text, "\"'`")
	return strings.Join(strings.Fields(text), " ")
}

type generatedTitle struct {
	Title string `json:"title" description:"Short descriptive chat title"`
}

type generatedTurnStatusLabel struct {
	Label string `json:"label" description:"Compact 2-5 word current chat status label"`
}

// GenerateChatTitleAsync fires a best-effort, automatic title-generation
// pass for a freshly created chat. It is intended to be called from the
// chat-creation endpoint right after the chat and its initial user
// message are persisted.
//
// The work runs in a tracked goroutine with a context detached from the
// request but bound to the server: it neither blocks the HTTP response
// nor is canceled when the request completes, and Close cancels it
// instead of blocking on the title timeout while a provider is
// unreachable. It resolves the chat's model and provider keys, then
// delegates to maybeGenerateChatTitle, which only acts on the first user
// turn (see titleInput) and is otherwise a no-op. Errors are logged and
// swallowed.
func (p *Server) GenerateChatTitleAsync(ctx context.Context, chat database.Chat) {
	logger := p.logger.With(
		slog.F("chat_id", chat.ID),
		slog.F("owner_id", chat.OwnerID),
	)
	// Snapshot the messages synchronously so the first-turn eligibility
	// check (titleInput) is evaluated against creation-time state. Loading
	// inside the goroutine would race the chat worker's first assistant
	// reply and could skip title generation.
	messages, err := p.db.GetChatMessagesForPromptByChatID(ctx, chat.ID)
	if err != nil {
		logger.Debug(ctx, "failed to load messages for automatic title generation",
			slog.Error(err),
		)
		return
	}
	pasteText, err := titlePasteText(ctx, p.db, messages)
	if err != nil {
		logger.Debug(ctx, "failed to load pasted-text attachments for automatic title generation",
			slog.Error(err),
		)
		return
	}
	if _, ok := titleInput(chat, messages, pasteText); !ok {
		return
	}
	// Detach from request; bind to server so Close cancels it.
	titleCtx, stopTitleCtx := p.inflightContext(ctx)
	if err := p.goInflight(func() {
		defer stopTitleCtx()
		apiKeyID, err := p.ensureSyntheticAPIKeyID(titleCtx, chat.OwnerID)
		if err != nil {
			logger.Debug(titleCtx, "failed to ensure synthetic API key for automatic title generation", slog.Error(err))
			return
		}
		modelOpts := modelBuildOptions{ActiveAPIKeyID: apiKeyID}
		turnCtx := titleCtx
		fallback, err := p.resolveModelCall(turnCtx, modelCallSpec{
			purpose:      "title",
			chat:         chat,
			buildOptions: modelOpts,
		})
		if err != nil {
			logger.Debug(titleCtx, "failed to resolve model for automatic title generation",
				slog.Error(err),
			)
			return
		}
		p.maybeGenerateChatTitle(
			turnCtx,
			chat,
			messages,
			pasteText,
			fallback,
			modelOpts,
			&generatedChatTitle{},
			logger,
			p.existingDebugService(),
		)
	}); err != nil {
		stopTitleCtx()
		logger.Error(context.WithoutCancel(ctx), "failed to schedule automatic chat title generation",
			slog.F("chat_id", chat.ID),
			slog.F("owner_id", chat.OwnerID),
			slog.Error(err),
		)
	}
}

// maybeGenerateChatTitle generates an AI title for the chat when
// appropriate (first user message, no assistant reply yet, and the
// current title is either empty or still the fallback truncation).
// It uses the configured title generation model override when set.
// Otherwise, it tries cheap, fast models first and falls back to the
// user's chat model. It is a best-effort operation that logs and
// swallows errors.
func (p *Server) maybeGenerateChatTitle(
	ctx context.Context,
	chat database.Chat,
	messages []database.ChatMessage,
	pasteText map[uuid.UUID]string,
	fallback resolvedModelCall,
	modelOpts modelBuildOptions,
	generatedTitle *generatedChatTitle,
	logger slog.Logger,
	debugSvc *chatdebug.Service,
) {
	input, ok := titleInput(chat, messages, pasteText)
	if !ok {
		return
	}
	debugEnabled := debugSvc != nil && debugSvc.IsEnabled(ctx, chat.ID, chat.OwnerID)

	titleCtx, cancel := context.WithTimeout(ctx, 30*time.Second)
	defer cancel()

	overrideResolved, overrideSet, overrideErr := p.resolveTitleGenerationModelOverride(
		titleCtx,
		chat,
		modelOpts,
	)
	if overrideErr != nil {
		if overrideSet {
			logger.Warn(ctx, "title generation model override unavailable, skipping title generation",
				slog.F("chat_id", chat.ID),
				slog.F("override_context", titleGenerationOverrideContext),
				slog.Error(overrideErr),
			)
			return
		}
		logger.Debug(ctx, "failed to resolve title generation model override",
			slog.F("chat_id", chat.ID),
			slog.F("override_context", titleGenerationOverrideContext),
			slog.Error(overrideErr),
		)
	}

	selected := fallback
	if overrideSet {
		selected = overrideResolved
	}
	candidate := shortTextCandidate{
		provider: string(selected.route.Provider.Type),
		model:    selected.dbConfig.Model,
		resolved: selected,
	}

	var historyTipMessageID int64
	if len(messages) > 0 {
		historyTipMessageID = messages[len(messages)-1].ID
	}

	var triggerMessageID int64
	for _, message := range messages {
		if message.Visibility == database.ChatMessageVisibilityModel {
			continue
		}
		if message.Role == database.ChatMessageRoleUser {
			triggerMessageID = message.ID
			break
		}
	}

	seedSummary := chatdebug.SeedSummary(
		chatdebug.TruncateLabel(input, chatdebug.MaxLabelLength),
	)

	candidateCtx := titleCtx
	finishDebugRun := func(error) {}
	if debugEnabled {
		candidateCtx, finishDebugRun = prepareQuickgenDebugCandidate(
			titleCtx,
			chat,
			debugSvc,
			candidate,
			chatdebug.KindTitleGeneration,
			triggerMessageID,
			historyTipMessageID,
			seedSummary,
			logger,
		)
	}

	title, err := generateTitle(candidateCtx, candidate.resolved.model.LanguageModel(), titleObjectCall(candidate.resolved), input)
	finishDebugRun(err)
	if err != nil {
		if overrideSet {
			logger.Warn(ctx, "title model candidate failed",
				slog.F("chat_id", chat.ID),
				slog.F("override_context", titleGenerationOverrideContext),
				slog.F("provider", candidate.provider),
				slog.F("model", candidate.model),
				slog.Error(err),
			)
		} else {
			logger.Debug(ctx, "title model candidate failed",
				slog.F("chat_id", chat.ID),
				slog.Error(err),
			)
		}
		return
	}
	if title == "" || title == chat.Title {
		return
	}

	_, err = p.db.UpdateChatTitleByID(ctx, database.UpdateChatTitleByIDParams{
		ID:    chat.ID,
		Title: title,
	})
	if err != nil {
		logger.Warn(ctx, "failed to update generated chat title",
			slog.F("chat_id", chat.ID),
			slog.Error(err),
		)
		return
	}
	chat.Title = title
	generatedTitle.Store(title)
	p.publishChatPubsubEvent(chat, codersdk.ChatWatchEventKindTitleChange, nil)
}

const titleMaxOutputTokens = int64(256)

func titleObjectCall(resolved resolvedModelCall) fantasy.ObjectCall {
	return resolved.newObjectCall("propose_title", "Propose a short chat title.", titleMaxOutputTokens)
}

func prepareQuickgenDebugCandidate(
	ctx context.Context,
	chat database.Chat,
	debugSvc *chatdebug.Service,
	candidate shortTextCandidate,
	kind chatdebug.RunKind,
	triggerMessageID int64,
	historyTipMessageID int64,
	seedSummary map[string]any,
	logger slog.Logger,
) (context.Context, func(error)) {
	finishDebugRun := func(error) {}

	// Debug instrumentation must not eat into the quickgen budget
	// (30s titleCtx / summaryCtx on the caller). Detach and bound
	// the insert so a slow DB can't delay title generation or push
	// summaries, matching prepareManualTitleDebugRun,
	// prepareChatTurnDebugRun, and startCompactionDebugRun.
	createRunCtx, createRunCancel := context.WithTimeout(
		context.WithoutCancel(ctx), debugCreateRunTimeout,
	)
	run, err := debugSvc.CreateRun(createRunCtx, chatdebug.CreateRunParams{
		ChatID:              chat.ID,
		TriggerMessageID:    triggerMessageID,
		HistoryTipMessageID: historyTipMessageID,
		Kind:                kind,
		Status:              chatdebug.StatusInProgress,
		Provider:            candidate.provider,
		Model:               candidate.model,
		Summary:             seedSummary,
	})
	createRunCancel()
	if err != nil {
		logger.Warn(ctx, "failed to create short-text debug run",
			slog.F("chat_id", chat.ID),
			slog.F("run_kind", kind),
			slog.F("provider", candidate.provider),
			slog.F("model", candidate.model),
			slog.Error(err),
		)
		return ctx, finishDebugRun
	}

	runContext := chatdebugRunContext(run)
	runCtx := chatdebug.ContextWithRun(ctx, &runContext)
	finishDebugRun = func(runErr error) {
		if finalizeErr := debugSvc.FinalizeRun(ctx, chatdebug.FinalizeRunParams{
			RunID:       run.ID,
			ChatID:      chat.ID,
			Status:      chatdebug.ClassifyError(runErr),
			SeedSummary: seedSummary,
			Timeout:     10 * time.Second,
		}); finalizeErr != nil {
			logger.Warn(ctx, "failed to finalize short-text debug run",
				slog.F("chat_id", chat.ID),
				slog.F("run_kind", kind),
				slog.F("run_id", run.ID),
				slog.Error(finalizeErr),
			)
		}
	}
	return runCtx, finishDebugRun
}

func quickgenPrompt(systemPrompt, userInput string) fantasy.Prompt {
	return fantasy.Prompt{
		{
			Role: fantasy.MessageRoleSystem,
			Content: []fantasy.MessagePart{
				fantasy.TextPart{Text: systemPrompt},
			},
		},
		{
			Role: fantasy.MessageRoleUser,
			Content: []fantasy.MessagePart{
				fantasy.TextPart{Text: userInput},
			},
		},
	}
}

// generateTitle calls the model with a title-generation system prompt
// and returns the normalized result. It retries transient LLM errors
// (rate limits, overloaded, etc.) with exponential backoff.
func generateTitle(
	ctx context.Context,
	model fantasy.LanguageModel,
	call fantasy.ObjectCall,
	input string,
) (string, error) {
	title, err := generateStructuredTitle(ctx, model, call, titleGenerationPrompt, input)
	if err != nil {
		return "", err
	}
	return title, nil
}

func generateStructuredTitle(
	ctx context.Context,
	model fantasy.LanguageModel,
	call fantasy.ObjectCall,
	systemPrompt string,
	userInput string,
) (string, error) {
	title, _, err := generateStructuredTitleWithUsage(
		ctx,
		model,
		call,
		systemPrompt,
		userInput,
	)
	if err != nil {
		return "", err
	}
	return title, nil
}

func generateStructuredTitleWithUsage(
	ctx context.Context,
	model fantasy.LanguageModel,
	call fantasy.ObjectCall,
	systemPrompt string,
	userInput string,
) (string, fantasy.Usage, error) {
	userInput = strings.TrimSpace(userInput)
	if userInput == "" {
		return "", fantasy.Usage{}, xerrors.New("title input was empty")
	}

	call.Prompt = quickgenPrompt(systemPrompt, userInput)
	result, err := generateQuickgenObject[generatedTitle](ctx, model, call)
	if err != nil {
		var usage fantasy.Usage
		var noObjErr *fantasy.NoObjectGeneratedError
		if errors.As(err, &noObjErr) {
			usage = noObjErr.Usage
		}
		return "", usage, xerrors.Errorf("generate structured title: %w", err)
	}

	title := normalizeTitleOutput(result.Object.Title)
	if err := validateGeneratedTitle(title); err != nil {
		return "", result.Usage, err
	}
	return title, result.Usage, nil
}

func validateGeneratedTitle(title string) error {
	if title == "" {
		return xerrors.New("generated title was empty")
	}
	if len(strings.Fields(title)) > 8 {
		return xerrors.New("generated title exceeded 8 words")
	}
	return nil
}

// titleInput returns the first user message title text and whether
// title generation should proceed. It returns false when the chat
// already has assistant/tool replies, has more than one visible user
// message, or the current title doesn't look like a candidate for
// replacement. pasteText carries resolved pasted-text attachment
// content (see titlePasteText) so paste-only messages stay eligible.
func titleInput(
	chat database.Chat,
	messages []database.ChatMessage,
	pasteText map[uuid.UUID]string,
) (string, bool) {
	userCount := 0
	firstUserText := ""

	for _, message := range messages {
		if message.Visibility == database.ChatMessageVisibilityModel {
			continue
		}

		switch message.Role {
		case database.ChatMessageRoleAssistant, database.ChatMessageRoleTool:
			return "", false
		case database.ChatMessageRoleUser:
			userCount++
			if firstUserText == "" {
				parsed, err := chatprompt.ParseContent(message)
				if err != nil {
					return "", false
				}
				firstUserText = chatprompt.TitleText(parsed, pasteText)
			}
		}
	}

	if userCount != 1 || firstUserText == "" {
		return "", false
	}

	currentTitle := strings.TrimSpace(chat.Title)
	if currentTitle == "" {
		return firstUserText, true
	}

	if currentTitle != chatprompt.FallbackTitle(firstUserText) {
		return "", false
	}

	return firstUserText, true
}

// titlePasteText resolves synthetic pasted-text attachment content
// for visible user messages whose text and file-reference parts yield
// no title input, fetching only bounded prefixes for
// chatprompt.TitleText. It returns nil without touching the database
// when every user message already has text.
func titlePasteText(
	ctx context.Context,
	store database.Store,
	messages []database.ChatMessage,
) (map[uuid.UUID]string, error) {
	var ids []uuid.UUID
	for _, message := range messages {
		if message.Visibility == database.ChatMessageVisibilityModel {
			continue
		}
		if message.Role != database.ChatMessageRoleUser {
			continue
		}
		parsed, err := chatprompt.ParseContent(message)
		if err != nil {
			continue
		}
		if chatprompt.TitleText(parsed, nil) != "" {
			continue
		}
		ids = append(ids, chatprompt.SyntheticPasteFileIDs(parsed)...)
	}
	if len(ids) == 0 {
		return nil, nil //nolint:nilnil // Nil map cleanly signals no paste content to resolve.
	}

	rows, err := store.GetChatFileDataPrefixesByIDs(ctx, database.GetChatFileDataPrefixesByIDsParams{
		IDs:         ids,
		PrefixBytes: chatprompt.TitlePasteBytePrefix,
	})
	if err != nil {
		return nil, xerrors.Errorf("get pasted-text chat file prefixes: %w", err)
	}
	pasteText := make(map[uuid.UUID]string, len(rows))
	for _, row := range rows {
		pasteText[row.ID] = chatprompt.TitlePasteText(row.DataPrefix)
	}
	return pasteText, nil
}

func normalizeTitleOutput(title string) string {
	title = normalizeShortTextOutput(title)
	if title == "" {
		return ""
	}
	return truncateRunes(title, 80)
}

// contentBlocksToText concatenates the text parts of SDK chat
// message parts into a single space-separated string.
func contentBlocksToText(parts []codersdk.ChatMessagePart) string {
	texts := make([]string, 0, len(parts))
	for _, part := range parts {
		if part.Type != codersdk.ChatMessagePartTypeText {
			continue
		}
		text := strings.TrimSpace(part.Text)
		if text == "" {
			continue
		}
		texts = append(texts, text)
	}
	return strings.Join(texts, " ")
}

func truncateRunes(value string, maxLen int) string {
	if maxLen <= 0 {
		return ""
	}
	runes := []rune(value)
	if len(runes) <= maxLen {
		return value
	}
	return string(runes[:maxLen])
}

// Manual title regeneration is user-initiated and can use richer
// conversation context than the automatic first-message title path
// above. These helpers keep the manual prompt-building logic private
// while reusing the shared title-generation utilities in this file.
type manualTitleTurn struct {
	role string
	text string
}

// extractManualTitleTurns flattens visible user and assistant
// messages into title turns. pasteText carries resolved pasted-text
// attachment content (see titlePasteText) so paste-only user messages
// still produce turns.
func extractManualTitleTurns(
	messages []database.ChatMessage,
	pasteText map[uuid.UUID]string,
) []manualTitleTurn {
	turns := make([]manualTitleTurn, 0, len(messages))
	for _, message := range messages {
		if message.Visibility == database.ChatMessageVisibilityModel {
			continue
		}

		role := ""
		switch message.Role {
		case database.ChatMessageRoleUser:
			role = string(database.ChatMessageRoleUser)
		case database.ChatMessageRoleAssistant:
			role = string(database.ChatMessageRoleAssistant)
		default:
			continue
		}

		parts, err := chatprompt.ParseContent(message)
		if err != nil {
			continue
		}

		text := chatprompt.TitleText(parts, pasteText)
		if text == "" {
			continue
		}

		turns = append(turns, manualTitleTurn{
			role: role,
			text: text,
		})
	}

	return turns
}

func selectManualTitleTurnIndexes(turns []manualTitleTurn) []int {
	firstUserIndex := slices.IndexFunc(turns, func(turn manualTitleTurn) bool {
		return turn.role == string(database.ChatMessageRoleUser)
	})
	if firstUserIndex == -1 {
		return nil
	}

	windowStart := max(0, len(turns)-recentTurnWindow)
	selected := make([]int, 0, recentTurnWindow+1)
	if firstUserIndex < windowStart {
		selected = append(selected, firstUserIndex)
	}
	for i := windowStart; i < len(turns); i++ {
		selected = append(selected, i)
	}

	return selected
}

func buildManualTitleContext(
	turns []manualTitleTurn,
	selected []int,
) (conversationBlock string, latestUserMsg string) {
	userCount := 0
	for _, turn := range turns {
		if turn.role != string(database.ChatMessageRoleUser) {
			continue
		}
		userCount++
		latestUserMsg = turn.text
	}

	latestUserMsg = truncateRunes(latestUserMsg, maxLatestUserMessageRunes)
	if userCount <= 1 || len(selected) == 0 {
		return "", latestUserMsg
	}

	lines := make([]string, 0, len(selected)+1)
	for i, idx := range selected {
		if i == 1 {
			if gap := idx - selected[i-1] - 1; gap > 0 {
				lines = append(lines, fmt.Sprintf("[... %d earlier turns omitted ...]", gap))
			}
		}
		lines = append(lines, fmt.Sprintf("[%s]: %s", turns[idx].role, turns[idx].text))
	}

	conversationBlock = strings.Join(lines, "\n")
	conversationBlock = truncateRunes(conversationBlock, maxConversationContextRunes)
	return conversationBlock, latestUserMsg
}

func renderManualTitlePrompt(
	conversationBlock string,
	firstUserText string,
	latestUserMsg string,
) string {
	var prompt strings.Builder
	write := func(value string) {
		_, _ = prompt.WriteString(value)
	}

	write("Write a short title for this AI coding conversation.\n")
	write("Populate the title field with the result.\n\n")
	write("Primary user objective:\n<primary_objective>\n")
	write(firstUserText)
	write("\n</primary_objective>")

	if conversationBlock != "" {
		write("\n\nConversation sample:\n<conversation_sample>\n")
		write(conversationBlock)
		write("\n</conversation_sample>")
	}

	if strings.TrimSpace(latestUserMsg) != strings.TrimSpace(truncateRunes(firstUserText, maxLatestUserMessageRunes)) {
		write("\n\nThe user's most recent message:\n<latest_message>\n")
		write(latestUserMsg)
		write("\n</latest_message>\n")
		write("Note: Weight the overall conversation arc more heavily than just the latest message.")
	}

	write("\n\nRequirements:\n")
	write("- Return only the title text in 2-8 words.\n")
	write("- Populate the title field only.\n")
	write("- Do not answer the user or describe the title-writing task.\n")
	write("- Preserve specific identifiers (PR numbers, repo names, file paths, function names, error messages).\n")
	write("- If the conversation is short or vague, stay close to the user's wording.\n")
	write("- Write the title in the same language as the user's messages.\n")
	write("- Sentence case. No quotes, emoji, markdown, or trailing punctuation.\n")
	return prompt.String()
}

func generateManualTitle(
	ctx context.Context,
	messages []database.ChatMessage,
	pasteText map[uuid.UUID]string,
	fallbackModel fantasy.LanguageModel,
	call fantasy.ObjectCall,
) (string, error) {
	turns := extractManualTitleTurns(messages, pasteText)
	selected := selectManualTitleTurnIndexes(turns)

	firstUserIndex := slices.IndexFunc(turns, func(turn manualTitleTurn) bool {
		return turn.role == string(database.ChatMessageRoleUser)
	})
	if firstUserIndex == -1 {
		return "", nil
	}
	firstUserText := truncateRunes(turns[firstUserIndex].text, maxLatestUserMessageRunes)

	conversationBlock, latestUserMsg := buildManualTitleContext(turns, selected)
	systemPrompt := renderManualTitlePrompt(
		conversationBlock,
		firstUserText,
		latestUserMsg,
	)

	titleCtx, cancel := context.WithTimeout(ctx, 30*time.Second)
	defer cancel()

	userInput := strings.TrimSpace(latestUserMsg)
	if userInput == "" {
		userInput = strings.TrimSpace(firstUserText)
	}

	title, _, err := generateStructuredTitleWithUsage(
		titleCtx,
		fallbackModel,
		call,
		systemPrompt,
		userInput,
	)
	if err != nil {
		return "", err
	}

	return title, nil
}

const chatSummaryGenerationPrompt = "You summarize an AI coding chat for a quick-reference popover. " +
	"Populate the summary field with 1 to 3 plain sentences describing what the conversation is about and what was accomplished or attempted. " +
	"Write about the conversation in the third person. " +
	"Preserve specific identifiers such as PR numbers, repo names, file paths, function names, and error messages. " +
	"Do not address the user, give instructions, or continue the task. " +
	"No markdown, lists, headings, code fences, or surrounding quotes."

const (
	// Bound the transcript so the summary call stays cheap and within context;
	// long chats keep head and tail turns (see renderChatSummaryTranscript).
	summaryTranscriptMaxRunes = 16000
	// Cap a single turn so one long message cannot dominate the budget.
	summaryTranscriptPerMessageMaxRunes = 4000
	summaryMaxOutputTokens              = 512
	// Reject pathologically long or verbose summaries, with slack over the
	// 1-3 sentence target.
	summaryMaxRunes     = 1000
	summaryMaxSentences = 6
)

type generatedChatSummary struct {
	Summary string `json:"summary" description:"1-3 sentence summary of the whole chat"`
}

// renderChatSummaryTranscript renders chat history as plain text for summary
// generation. Plain text avoids provider tool-call pairing rules.
func renderChatSummaryTranscript(messages []database.ChatMessage) string {
	lines := make([]string, 0, len(messages))
	for _, message := range messages {
		var role string
		switch message.Role {
		case database.ChatMessageRoleUser:
			role = "user"
		case database.ChatMessageRoleAssistant:
			role = "assistant"
		default:
			continue
		}

		// Keep visible turns plus the compaction summary (model-only but
		// compressed); skip other model-only messages as noise.
		visible := message.Visibility == database.ChatMessageVisibilityBoth ||
			message.Visibility == database.ChatMessageVisibilityUser
		compactionSummary := message.Visibility == database.ChatMessageVisibilityModel &&
			message.Compressed
		if !visible && !compactionSummary {
			continue
		}

		parts, err := chatprompt.ParseContent(message)
		if err != nil {
			continue
		}
		text := strings.TrimSpace(contentBlocksToText(parts))
		if text == "" {
			continue
		}
		text = truncateRunes(text, summaryTranscriptPerMessageMaxRunes)
		lines = append(lines, fmt.Sprintf("[%s]: %s", role, text))
	}
	return boundTranscriptHeadTail(lines, summaryTranscriptMaxRunes)
}

// boundTranscriptHeadTail joins lines; if over maxRunes it keeps a head and
// tail slice with an elision marker between, preserving the chat's start and
// most recent activity.
func boundTranscriptHeadTail(lines []string, maxRunes int) string {
	if len(lines) == 0 {
		return ""
	}
	total := 0
	for _, line := range lines {
		total += len([]rune(line)) + 1
	}
	if total <= maxRunes {
		return strings.Join(lines, "\n")
	}

	half := maxRunes / 2
	headEnd := 0
	headRunes := 0
	for headEnd < len(lines) {
		n := len([]rune(lines[headEnd])) + 1
		if headEnd > 0 && headRunes+n > half {
			break
		}
		headRunes += n
		headEnd++
	}
	tailStart := len(lines)
	tailRunes := 0
	for tailStart > headEnd {
		n := len([]rune(lines[tailStart-1])) + 1
		if tailRunes+n > half {
			break
		}
		tailRunes += n
		tailStart--
	}

	var out strings.Builder
	writeLine := func(line string) {
		if out.Len() > 0 {
			_ = out.WriteByte('\n')
		}
		_, _ = out.WriteString(line)
	}

	for _, line := range lines[:headEnd] {
		writeLine(line)
	}
	if tailStart > headEnd {
		writeLine("[... earlier turns omitted ...]")
	}
	for _, line := range lines[tailStart:] {
		writeLine(line)
	}
	return out.String()
}

func summaryObjectCall(resolved resolvedModelCall) fantasy.ObjectCall {
	return resolved.newObjectCall("chat_summary", "Summarize the whole chat in 1-3 sentences.", summaryMaxOutputTokens)
}

// generateChatSummary generates a 1-3 sentence whole-chat summary from a
// transcript. A blank or invalid result returns an error so callers preserve
// any existing summary rather than clearing it.
func generateChatSummary(
	ctx context.Context,
	model fantasy.LanguageModel,
	call fantasy.ObjectCall,
	transcript string,
) (string, fantasy.Usage, error) {
	transcript = strings.TrimSpace(transcript)
	if transcript == "" {
		return "", fantasy.Usage{}, xerrors.New("chat summary transcript was empty")
	}

	call.Prompt = quickgenPrompt(chatSummaryGenerationPrompt, transcript)
	var result *fantasy.ObjectResult[generatedChatSummary]
	err := chatretry.Retry(ctx, func(retryCtx context.Context) error {
		var genErr error
		result, genErr = object.Generate[generatedChatSummary](retryCtx, model, call)
		return genErr
	}, nil)
	if err != nil {
		var usage fantasy.Usage
		if noObjErr, ok := errors.AsType[*fantasy.NoObjectGeneratedError](err); ok {
			usage = noObjErr.Usage
		}
		return "", usage, xerrors.Errorf("generate chat summary: %w", err)
	}

	summary := normalizeShortTextOutput(result.Object.Summary)
	if err := validateGeneratedChatSummary(summary); err != nil {
		return "", result.Usage, err
	}
	return summary, result.Usage, nil
}

func validateGeneratedChatSummary(summary string) error {
	if summary == "" {
		return xerrors.New("generated chat summary was empty")
	}
	if len([]rune(summary)) > summaryMaxRunes {
		return xerrors.Errorf("generated chat summary exceeded %d runes", summaryMaxRunes)
	}
	if countSentenceTerminators(summary) > summaryMaxSentences {
		return xerrors.Errorf("generated chat summary exceeded %d sentences", summaryMaxSentences)
	}
	return nil
}

// countSentenceTerminators counts sentence-ending punctuation, but only when
// followed by whitespace or end-of-text, so periods inside dotted identifiers
// (pkg.cmd.server, file paths) do not inflate the count.
func countSentenceTerminators(text string) int {
	runes := []rune(text)
	count := 0
	for i, r := range runes {
		if r != '.' && r != '!' && r != '?' {
			continue
		}
		if i == len(runes)-1 || unicode.IsSpace(runes[i+1]) {
			count++
		}
	}
	return count
}

// markdownLinkRe matches inline links and images so snippet extraction
// can keep the link text and drop the URL.
var markdownLinkRe = regexp.MustCompile(`!?\[([^\]]*)\]\([^)]*\)`)

func subagentReportSummarySnippet(report string) string {
	paragraph := firstReportParagraph(report)
	if paragraph == "" {
		return ""
	}
	return boundSnippetSentences(
		paragraph,
		subagentReportSummaryMaxSentences,
		subagentReportSummaryMaxRunes,
	)
}

func firstReportParagraph(report string) string {
	var paragraph []string
	inFence := false
	for line := range strings.Lines(report) {
		trimmed := strings.TrimSpace(line)
		if strings.HasPrefix(trimmed, "```") || strings.HasPrefix(trimmed, "~~~") {
			if !inFence && len(paragraph) > 0 {
				break
			}
			inFence = !inFence
			continue
		}
		if inFence {
			continue
		}
		if trimmed == "" || isMarkdownStructureLine(trimmed) {
			if len(paragraph) > 0 {
				break
			}
			continue
		}
		content := stripInlineMarkdown(stripLineMarkers(trimmed))
		if content == "" {
			if len(paragraph) > 0 {
				break
			}
			continue
		}
		paragraph = append(paragraph, content)
	}
	return strings.TrimSpace(strings.Join(paragraph, " "))
}

func isMarkdownStructureLine(trimmed string) bool {
	if strings.HasPrefix(trimmed, "#") || strings.HasPrefix(trimmed, "|") {
		return true
	}
	// Horizontal rules: at least three of the same marker character
	// and nothing else.
	if len(trimmed) >= 3 && strings.Trim(trimmed, "-") == "" {
		return true
	}
	if len(trimmed) >= 3 && strings.Trim(trimmed, "*") == "" {
		return true
	}
	if len(trimmed) >= 3 && strings.Trim(trimmed, "_") == "" {
		return true
	}
	return false
}

func stripLineMarkers(trimmed string) string {
	for {
		next := trimmed
		next = strings.TrimPrefix(next, ">")
		if rest, ok := trimListMarker(next); ok {
			next = rest
		}
		next = strings.TrimSpace(next)
		if next == trimmed {
			return trimmed
		}
		trimmed = next
	}
}

// trimListMarker strips one leading bullet ("- ", "* ", "+ "), ordered
// ("1. ", "1) "), or task-list ("[ ] ", "[x] ") marker.
func trimListMarker(line string) (string, bool) {
	for _, marker := range []string{"- ", "* ", "+ ", "[ ] ", "[x] ", "[X] "} {
		if rest, ok := strings.CutPrefix(line, marker); ok {
			return rest, true
		}
	}
	digits := 0
	for _, r := range line {
		if r < '0' || r > '9' {
			break
		}
		digits++
	}
	if digits > 0 && len(line) > digits+1 &&
		(line[digits] == '.' || line[digits] == ')') && line[digits+1] == ' ' {
		return line[digits+2:], true
	}
	return line, false
}

func stripInlineMarkdown(text string) string {
	text = markdownLinkRe.ReplaceAllString(text, "$1")
	replacer := strings.NewReplacer("**", "", "__", "", "~~", "", "`", "")
	return strings.TrimSpace(replacer.Replace(text))
}

func boundSnippetSentences(text string, maxSentences, maxRunes int) string {
	runes := []rune(text)
	sentences := 0
	lastEnd := 0
	for i, r := range runes {
		if r != '.' && r != '!' && r != '?' {
			continue
		}
		if i != len(runes)-1 && !unicode.IsSpace(runes[i+1]) {
			continue
		}
		if i+1 > maxRunes {
			break
		}
		lastEnd = i + 1
		sentences++
		if sentences >= maxSentences {
			break
		}
	}
	if lastEnd > 0 {
		return strings.TrimSpace(string(runes[:lastEnd]))
	}
	if len(runes) <= maxRunes {
		return text
	}
	return strings.TrimSpace(string(runes[:maxRunes-1])) + "…"
}

const turnStatusLabelPrompt = "You write compact chat status labels for a sidebar or push notification. " +
	"Given a chat title, current chat state, and the agent's latest message, populate the label field with a 2-5 word status label. " +
	"Describe the chat's current state, not the agent. " +
	"Good examples: Finished unit tests, Submitted PR, Still working on API, Waiting for user input. " +
	"Do not start with Agent, I, We, It, The agent, or The chat. " +
	"Avoid phrases like Agent asked, Agent identified, Agent found, or Agent explained. " +
	"Prefer short action or state phrases such as Finished, Submitted, Fixed, Testing, Still working, or Waiting for. " +
	"No quotes, emoji, markdown, or trailing punctuation."

const turnStatusLabelMaxOutputTokens = int64(64)

func turnStatusLabelObjectCall(resolved resolvedModelCall) fantasy.ObjectCall {
	return resolved.newObjectCall("propose_turn_status_label", "Propose a compact chat status label.", turnStatusLabelMaxOutputTokens)
}

// generateTurnStatusLabel returns an empty string if generation fails.
func generateTurnStatusLabel(
	ctx context.Context,
	chat database.Chat,
	status database.ChatStatus,
	assistantText string,
	resolved resolvedModelCall,
	logger slog.Logger,
	debugSvc *chatdebug.Service,
	triggerMessageID int64,
	historyTipMessageID int64,
) string {
	debugEnabled := debugSvc != nil && debugSvc.IsEnabled(ctx, chat.ID, chat.OwnerID)

	labelCtx, cancel := context.WithTimeout(ctx, 30*time.Second)
	defer cancel()

	assistantText = truncateRunes(assistantText, maxConversationContextRunes)
	input := "Current chat state: " + turnStatusLabelStateContext(status) +
		"\nChat title: " + chat.Title +
		"\n\nAgent's latest message:\n" + assistantText

	candidate := shortTextCandidate{
		provider: resolved.resolvedProvider,
		model:    resolved.resolvedModel,
		resolved: resolved,
	}

	statusSeedSummary := chatdebug.SeedSummary("Turn status label")

	candidateCtx := labelCtx
	finishDebugRun := func(error) {}
	if debugEnabled {
		candidateCtx, finishDebugRun = prepareQuickgenDebugCandidate(
			labelCtx,
			chat,
			debugSvc,
			candidate,
			chatdebug.KindQuickgen,
			triggerMessageID,
			historyTipMessageID,
			statusSeedSummary,
			logger,
		)
	}

	generatedLabel, err := generateStructuredTurnStatusLabel(
		candidateCtx,
		candidate.resolved.model.LanguageModel(),
		turnStatusLabelObjectCall(resolved),
		turnStatusLabelPrompt,
		input,
	)
	finishDebugRun(err)
	if err != nil {
		logger.Debug(ctx, "turn status label model candidate failed",
			slog.Error(err),
		)
		return ""
	}
	return generatedLabel
}

func generateStructuredTurnStatusLabel(
	ctx context.Context,
	model fantasy.LanguageModel,
	call fantasy.ObjectCall,
	systemPrompt string,
	userInput string,
) (string, error) {
	userInput = strings.TrimSpace(userInput)
	if userInput == "" {
		return "", xerrors.New("turn status label input was empty")
	}

	call.Prompt = quickgenPrompt(systemPrompt, userInput)
	result, err := generateQuickgenObject[generatedTurnStatusLabel](ctx, model, call)
	if err != nil {
		return "", xerrors.Errorf("generate structured turn status label: %w", err)
	}

	label, ok := normalizeTurnStatusLabel(result.Object.Label)
	if !ok {
		return "", xerrors.New("generated turn status label was invalid")
	}
	return label, nil
}

func turnStatusLabelStateContext(status database.ChatStatus) string {
	switch status {
	case database.ChatStatusWaiting:
		return "The turn finished and the chat is idle."
	case database.ChatStatusRequiresAction:
		return "The chat is waiting for user input or action."
	case database.ChatStatusError:
		return "The chat ended with an error."
	default:
		return "The chat state is unknown."
	}
}

func fallbackTurnStatusLabel(status database.ChatStatus) string {
	switch status {
	case database.ChatStatusWaiting:
		return "Finished latest turn"
	case database.ChatStatusRequiresAction:
		return "Waiting for user input"
	case database.ChatStatusError:
		return "Hit an error"
	default:
		return "Updated chat status"
	}
}

func normalizeTurnStatusLabel(text string) (string, bool) {
	text = strings.TrimSpace(text)
	if text == "" {
		return "", false
	}

	text = strings.Trim(text, "\"'`")
	text = strings.TrimSpace(text)
	if text == "" || strings.ContainsAny(text, "\r\n") {
		return "", false
	}
	text = strings.TrimRight(text, ".!?")
	text = strings.Join(strings.Fields(text), " ")
	if text == "" || hasSentenceBoundary(text) {
		return "", false
	}

	words := strings.Fields(text)
	if len(words) < 2 || len(words) > 5 {
		return "", false
	}

	lower := strings.ToLower(text)
	if hasDisallowedTurnStatusLabelSubject(lower) {
		return "", false
	}

	disallowedPhrases := []string{
		"agent asked",
		"agent identified",
		"agent found",
		"agent explained",
	}
	for _, phrase := range disallowedPhrases {
		if strings.Contains(lower, phrase) {
			return "", false
		}
	}

	return text, true
}

func hasDisallowedTurnStatusLabelSubject(text string) bool {
	subject := leadingLetters(text)
	switch subject {
	case "agent", "i", "it", "the", "we":
		return true
	default:
		return false
	}
}

func leadingLetters(text string) string {
	for i, r := range text {
		if r < 'a' || r > 'z' {
			return text[:i]
		}
	}
	return text
}

func hasSentenceBoundary(text string) bool {
	for i, r := range text {
		switch r {
		case '.', '!', '?':
			if i+1 < len(text) && text[i+1] == ' ' {
				return true
			}
		}
	}
	return false
}