package openai

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"strings"
	"sync"
)

const defaultArtifactFrontierCapacity = 1024

type artifactFrontierPhase string

const (
	artifactPhasePinned         artifactFrontierPhase = "pinned"
	artifactPhasePreparePending artifactFrontierPhase = "prepare_pending"
	artifactPhasePairReady      artifactFrontierPhase = "pair_ready"
	artifactPhasePairPending    artifactFrontierPhase = "pair_pending"
	artifactPhaseLocalEligible  artifactFrontierPhase = "local_eligible"
)

type artifactDispositionKind string

const (
	artifactDispositionResumeSelector artifactDispositionKind = "resume_selector"
	artifactDispositionLocalEligible  artifactDispositionKind = "local_eligible"
)

type artifactDisposition struct {
	Kind            artifactDispositionKind
	SelectorStageID string
	PrimaryError    *hotPathEndpointError
}

// presetIngressResult carries a control decision that the public handler must
// consume before it can construct or submit another provider-pool request.
// It deliberately keeps the artifact disposition out of caller-controlled
// metadata, which is only a transport for trusted logical request IDs.
type presetIngressResult struct {
	Artifact artifactDisposition
	Light    hotPathLightDisposition
	Cleanup  *hotPathCleanupTurn
	Terminal *hotPathTerminalIntent
}

func (r presetIngressResult) localStageEligible() bool {
	return r.Artifact.Kind == artifactDispositionLocalEligible
}

func (r presetIngressResult) lightStageContinuation() bool {
	return r.Light.RequestID != "" && r.Light.Terminal == nil
}

func (r presetIngressResult) cleanupIssued() bool {
	return r.Cleanup != nil
}

func (r presetIngressResult) terminalReady() bool {
	return r.Terminal != nil
}

type artifactFrontierRecord struct {
	requestID       string
	ownerEdgeID     string
	principalRef    string
	protocol        string
	selectorStageID string
	lineage         logicalRequestLineage
	binding         *workspaceBinding
	phase           artifactFrontierPhase
	pending         map[string]*workspaceEncodedPayload
	pendingHash     string
	consumedHashes  map[string]struct{}
	consumedIDs     map[string]struct{}
}

// artifactFrontierStore owns the request-local workspace binding and the sole
// prepare/pair receipt frontier. Its fixed capacity prevents abandoned caller
// continuations from growing Edge-local state without bound.
type artifactFrontierStore struct {
	mu       sync.Mutex
	capacity int
	records  map[string]*artifactFrontierRecord
}

func newArtifactFrontierStore(capacity int) *artifactFrontierStore {
	if capacity <= 0 {
		capacity = defaultArtifactFrontierCapacity
	}
	return &artifactFrontierStore{capacity: capacity, records: make(map[string]*artifactFrontierRecord)}
}

func (s *artifactFrontierStore) pin(
	requestID, ownerEdgeID, principalRef, protocol, selectorStageID string,
	lineage logicalRequestLineage,
	binding *workspaceBinding,
) error {
	if s == nil || binding == nil {
		return fmt.Errorf("artifact frontier binding is unavailable")
	}
	if !validLogicalRequestID(requestID) || !validLogicalRequestID(selectorStageID) {
		return fmt.Errorf("artifact frontier identity is invalid")
	}
	if strings.TrimSpace(ownerEdgeID) == "" || strings.TrimSpace(principalRef) == "" {
		return fmt.Errorf("artifact frontier owner and principal are required")
	}
	if !artifactProtocolMatchesLineage(protocol, lineage) {
		return fmt.Errorf("artifact frontier protocol does not match request lineage")
	}

	s.mu.Lock()
	defer s.mu.Unlock()
	if _, exists := s.records[requestID]; exists {
		return fmt.Errorf("artifact frontier already exists")
	}
	if len(s.records) >= s.capacity {
		return fmt.Errorf("artifact frontier capacity reached")
	}
	s.records[requestID] = &artifactFrontierRecord{
		requestID: requestID, ownerEdgeID: ownerEdgeID, principalRef: principalRef,
		protocol: protocol, selectorStageID: selectorStageID, lineage: lineage,
		binding: binding, phase: artifactPhasePinned,
		consumedHashes: make(map[string]struct{}), consumedIDs: make(map[string]struct{}),
	}
	return nil
}

func artifactProtocolMatchesLineage(protocol string, lineage logicalRequestLineage) bool {
	switch protocol {
	case "openai":
		return lineage.Endpoint == logicalRequestEndpointChat
	case "anthropic":
		return lineage.Endpoint == logicalRequestEndpointAnthropic
	default:
		return false
	}
}

func (s *artifactFrontierStore) remove(requestID, ownerEdgeID string) {
	if s == nil || requestID == "" {
		return
	}
	s.mu.Lock()
	defer s.mu.Unlock()
	if record := s.records[requestID]; record != nil && record.ownerEdgeID == ownerEdgeID {
		delete(s.records, requestID)
	}
}

func (s *artifactFrontierStore) has(requestID, ownerEdgeID string) bool {
	if s == nil || requestID == "" {
		return false
	}
	s.mu.Lock()
	defer s.mu.Unlock()
	record := s.records[requestID]
	return record != nil && record.ownerEdgeID == ownerEdgeID
}

// pairRequired reports whether the retained selector may only author the
// exact Plan/Review pair. The store owns the phase and keeps this observation
// lock-safe so a handler cannot infer it from untrusted request metadata.
func (s *artifactFrontierStore) pairRequired(requestID, ownerEdgeID string) bool {
	if s == nil || requestID == "" {
		return false
	}
	s.mu.Lock()
	defer s.mu.Unlock()
	record := s.records[requestID]
	return record != nil && record.ownerEdgeID == ownerEdgeID && record.phase == artifactPhasePairReady
}

func (s *artifactFrontierStore) issue(
	turn *hotPathTurn,
	output normalizedStageOutput,
	coordinator *logicalRequestCoordinator,
) (normalizedStageOutput, error) {
	if s == nil || coordinator == nil || turn == nil {
		return normalizedStageOutput{}, fmt.Errorf("artifact frontier is unavailable")
	}

	s.mu.Lock()
	defer s.mu.Unlock()
	record := s.records[turn.RequestID]
	if record == nil {
		return normalizedStageOutput{}, fmt.Errorf("artifact frontier is not pinned")
	}
	if record.ownerEdgeID != turn.OwnerEdgeID || record.principalRef != turn.PrincipalRef {
		return normalizedStageOutput{}, fmt.Errorf("artifact frontier owner or principal mismatch")
	}
	if record.protocol != turn.Protocol || record.selectorStageID != turn.StageID {
		return normalizedStageOutput{}, fmt.Errorf("artifact frontier selector stage mismatch")
	}

	wantPrepare := false
	switch record.phase {
	case artifactPhasePinned:
		wantPrepare = !record.binding.createsParents()
	case artifactPhasePairReady:
		wantPrepare = false
	default:
		return normalizedStageOutput{}, fmt.Errorf("artifact frontier already has a pending or consumed turn")
	}

	mapped, payloads, err := mapArtifactOutput(record, output, wantPrepare, coordinator)
	if err != nil {
		return normalizedStageOutput{}, err
	}
	if turn.Protocol == "anthropic" {
		mapped.TerminalReason = "tool_use"
	}
	if turn.OuterTurn != nil {
		ctx := context.Background()
		if turn.Request != nil {
			ctx = turn.Request.Context()
		}
		if !output.ProgressivelyReleased {
			if err := runHotPathCollectedStage(ctx, turn.OuterTurn, turn.StageID, mapped); err != nil {
				return normalizedStageOutput{}, fmt.Errorf("collect artifact outer turn: %w", err)
			}
		}
		visible := hotPathCompatibilityOutput(turn.OuterTurn, mapped, turn.Protocol)
		if len(visible.ToolCalls) == 0 && turn.OuterTurn.outputBudget().Exhausted {
			turn.OuterTurn.commitLengthTerminal()
			return hotPathCompatibilityOutput(turn.OuterTurn, mapped, turn.Protocol), nil
		}
		if err := turn.OuterTurn.projectToolIdentities(mapped.ToolCalls); err != nil {
			return normalizedStageOutput{}, err
		}
		mapped = hotPathCompatibilityOutput(turn.OuterTurn, mapped, turn.Protocol)
	}
	issuedHash, err := directIssuedCallHash(turn.Protocol, mapped)
	if err != nil {
		return normalizedStageOutput{}, fmt.Errorf("fingerprint artifact calls: %w", err)
	}
	expected := make([]logicalRequestExpectedTool, 0, len(mapped.ToolCalls))
	for _, call := range mapped.ToolCalls {
		expected = append(expected, logicalRequestExpectedTool{
			PublicCallID: call.ID, ProviderCallID: call.ProviderCallID,
		})
	}
	if _, err := coordinator.awaitToolResults(
		turn.RequestID, turn.OwnerEdgeID, turn.StageID, expected, issuedHash,
	); err != nil {
		return normalizedStageOutput{}, fmt.Errorf("await artifact results: %w", err)
	}

	record.pending = payloads
	record.pendingHash = issuedHash
	if wantPrepare {
		record.phase = artifactPhasePreparePending
	} else {
		record.phase = artifactPhasePairPending
	}
	return mapped, nil
}

func mapArtifactOutput(
	record *artifactFrontierRecord,
	output normalizedStageOutput,
	wantPrepare bool,
	coordinator *logicalRequestCoordinator,
) (normalizedStageOutput, map[string]*workspaceEncodedPayload, error) {
	issued := newReservedPaths(record.requestID)
	calls := append([]normalizedToolCall(nil), output.ToolCalls...)
	if wantPrepare {
		if len(calls) != 1 {
			return normalizedStageOutput{}, nil, fmt.Errorf("artifact prepare turn must contain exactly one call")
		}
		mapped, payload, err := mapArtifactCall(record.binding, calls[0], opKindPrepare, issued.JobDir, coordinator)
		if err != nil {
			return normalizedStageOutput{}, nil, err
		}
		return artifactResponseOutput(output, []normalizedToolCall{mapped}), map[string]*workspaceEncodedPayload{mapped.ID: payload}, nil
	}

	if len(calls) != 2 {
		return normalizedStageOutput{}, nil, fmt.Errorf("artifact pair turn must contain exactly two calls")
	}
	byPath := make(map[string]normalizedToolCall, len(calls))
	for _, call := range calls {
		paths := reservedPathsFromToolCall(call)
		if len(paths) != 1 {
			return normalizedStageOutput{}, nil, fmt.Errorf("artifact pair call has an ambiguous reserved path")
		}
		clean := cleanRelativePath(paths[0])
		if _, duplicate := byPath[clean]; duplicate {
			return normalizedStageOutput{}, nil, fmt.Errorf("artifact pair contains a duplicate path")
		}
		byPath[clean] = call
	}

	orderedPaths := []string{issued.PlanPath, issued.ReviewPath}
	mappedCalls := make([]normalizedToolCall, 0, 2)
	payloads := make(map[string]*workspaceEncodedPayload, 2)
	for _, requiredPath := range orderedPaths {
		call, ok := byPath[cleanRelativePath(requiredPath)]
		if !ok {
			return normalizedStageOutput{}, nil, fmt.Errorf("artifact pair is missing reserved path %q", requiredPath)
		}
		mapped, payload, err := mapArtifactCall(record.binding, call, opKindWrite, requiredPath, coordinator)
		if err != nil {
			return normalizedStageOutput{}, nil, err
		}
		mappedCalls = append(mappedCalls, mapped)
		payloads[mapped.ID] = payload
	}
	return artifactResponseOutput(output, mappedCalls), payloads, nil
}

func mapArtifactCall(
	binding *workspaceBinding,
	providerCall normalizedToolCall,
	operation workspaceOperationKind,
	requiredPath string,
	coordinator *logicalRequestCoordinator,
) (normalizedToolCall, *workspaceEncodedPayload, error) {
	providerID := strings.TrimSpace(providerCall.ProviderCallID)
	if providerID == "" {
		providerID = strings.TrimSpace(providerCall.ID)
	}
	if !validLogicalRequestID(providerID) {
		return normalizedToolCall{}, nil, fmt.Errorf("artifact provider tool id is invalid")
	}
	publicID, err := coordinator.newCallID()
	if err != nil {
		return normalizedToolCall{}, nil, fmt.Errorf("allocate artifact public tool id: %w", err)
	}
	providerCall.ID = publicID
	providerCall.ProviderCallID = providerID
	payload, err := encodeWorkspaceCall(binding, operation, providerCall)
	if err != nil {
		return normalizedToolCall{}, nil, fmt.Errorf("encode artifact %s call: %w", operation, err)
	}
	if payload.safePath != cleanRelativePath(requiredPath) {
		return normalizedToolCall{}, nil, fmt.Errorf("artifact call targets %q, want %q", payload.safePath, requiredPath)
	}
	rawArgs, err := json.Marshal(payload.structuredArgs)
	if err != nil {
		return normalizedToolCall{}, nil, fmt.Errorf("encode artifact arguments: %w", err)
	}
	mapped := normalizedToolCall{
		ID: publicID, ProviderCallID: providerID, Name: payload.toolName,
		Arguments: cloneAnyMap(payload.structuredArgs), RawArgs: string(rawArgs), Path: payload.safePath,
	}
	return mapped, payload, nil
}

func artifactResponseOutput(source normalizedStageOutput, calls []normalizedToolCall) normalizedStageOutput {
	return normalizedStageOutput{
		ResponseID: source.ResponseID, Created: source.Created, Content: source.Content,
		Reasoning: source.Reasoning, ReasoningSignature: source.ReasoningSignature, ToolCalls: calls,
		TerminalReason: "tool_calls", Usage: cloneRawJSON(source.Usage), OpenAIUsage: source.OpenAIUsage,
	}
}

func (s *Server) runArtifactPairTurn(turn *hotPathTurn, output normalizedStageOutput, gate hotPathSelectorGate) error {
	if turn == nil {
		return fmt.Errorf("artifact turn is unavailable")
	}
	if strings.TrimSpace(turn.PrincipalRef) == "" {
		turn.PrincipalRef = strings.TrimSpace(turn.Dispatch.PrincipalRef)
		if turn.PrincipalRef == "" {
			turn.PrincipalRef = "anonymous"
		}
	}
	mapped, err := s.artifactFrontiers.issue(turn, output, s.requestCoordinator)
	if err != nil {
		s.terminalPresetRequest(turn.RequestID, turn.OwnerEdgeID)
		return s.writeDirectError(turn, 400, "invalid_request_error", fmt.Sprintf("artifact turn rejected: %v", err))
	}
	if turn.OuterTurn != nil && len(mapped.ToolCalls) == 0 && turn.OuterTurn.outputBudget().Exhausted {
		s.terminalPresetRequest(turn.RequestID, turn.OwnerEdgeID)
		return s.writeDirectResponse(turn, mapped)
	}
	if s.lightFlows.has(turn.RequestID, turn.OwnerEdgeID) {
		if err := s.lightFlows.commitSelector(turn.RequestID, turn.OwnerEdgeID, output, gate); err != nil {
			s.terminalPresetRequest(turn.RequestID, turn.OwnerEdgeID)
			return s.writeDirectError(turn, 400, "invalid_request_error", fmt.Sprintf("light selector commit rejected: %v", err))
		}
	}
	if turn.OuterTurn != nil {
		turn.OuterTurn.commitTerminalSuccess(mapped.TerminalReason)
		mapped = hotPathCompatibilityOutput(turn.OuterTurn, mapped, turn.Protocol)
	}
	if err := s.writeDirectResponse(turn, mapped); err != nil {
		s.terminalPresetRequest(turn.RequestID, turn.OwnerEdgeID)
		return err
	}
	return nil
}

func (s *Server) applyArtifactDisposition(
	snap logicalRequestSnapshot,
	disposition artifactDisposition,
	metadata map[string]string,
) error {
	if metadata == nil {
		return fmt.Errorf("artifact continuation metadata is unavailable")
	}
	callID, err := s.requestCoordinator.newCallID()
	if err != nil {
		return err
	}
	metadata["iop_logical_request_id"] = snap.ID
	metadata["iop_call_id"] = callID
	metadata["iop_stage_id"] = disposition.SelectorStageID
	return nil
}

func (s *artifactFrontierStore) consumeChat(
	ownerEdgeID, principalRef string,
	rawBody []byte,
	lineage logicalRequestContinuationLineage,
	coordinator *logicalRequestCoordinator,
	lightFlows *hotPathLightStore,
) (logicalRequestSnapshot, artifactDisposition, bool, error) {
	results, err := decodeChatWorkspaceResults(rawBody)
	if err != nil {
		return logicalRequestSnapshot{}, artifactDisposition{}, true, err
	}
	return s.consume(ownerEdgeID, principalRef, "openai", lineage, results, coordinator, lightFlows)
}

func (s *artifactFrontierStore) consumeAnthropic(
	ownerEdgeID, principalRef string,
	rawBody []byte,
	lineage logicalRequestContinuationLineage,
	coordinator *logicalRequestCoordinator,
	lightFlows *hotPathLightStore,
) (logicalRequestSnapshot, artifactDisposition, bool, error) {
	results, err := decodeAnthropicWorkspaceResults(rawBody)
	if err != nil {
		return logicalRequestSnapshot{}, artifactDisposition{}, true, err
	}
	return s.consume(ownerEdgeID, principalRef, "anthropic", lineage, results, coordinator, lightFlows)
}

func (s *artifactFrontierStore) consume(
	ownerEdgeID, principalRef, protocol string,
	lineage logicalRequestContinuationLineage,
	results []workspaceResult,
	coordinator *logicalRequestCoordinator,
	lightFlows *hotPathLightStore,
) (logicalRequestSnapshot, artifactDisposition, bool, error) {
	if s == nil || coordinator == nil {
		return logicalRequestSnapshot{}, artifactDisposition{}, false, nil
	}
	s.mu.Lock()
	defer s.mu.Unlock()
	record, matched, err := s.matchRecordLocked(ownerEdgeID, principalRef, protocol, lineage)
	if !matched || err != nil {
		return logicalRequestSnapshot{}, artifactDisposition{}, matched, err
	}
	if record.pending == nil || record.pendingHash == "" {
		return logicalRequestSnapshot{}, artifactDisposition{}, true, fmt.Errorf("artifact frontier has no pending calls")
	}
	if len(results) != len(record.pending) {
		return logicalRequestSnapshot{}, artifactDisposition{}, true, fmt.Errorf("artifact result set size mismatch")
	}
	seen := make(map[string]struct{}, len(results))
	var primaryFailure *hotPathEndpointError
	for _, result := range results {
		payload := record.pending[result.callID]
		if payload == nil {
			return logicalRequestSnapshot{}, artifactDisposition{}, true, fmt.Errorf("artifact result id is not in the pending frontier")
		}
		if _, duplicate := seen[result.callID]; duplicate {
			return logicalRequestSnapshot{}, artifactDisposition{}, true, fmt.Errorf("artifact result id is duplicated")
		}
		seen[result.callID] = struct{}{}
		receipt := matchResultReceipt(record.binding, payload, result)
		if !receipt.matched {
			// A valid request lineage, pending call, and immutable issue
			// correlation route an exact receipt-matcher failure to primary
			// cleanup without trusting the result as a success. An invalid issue
			// correlation, or an opaque/malformed result that is not an exact
			// caller report, stays an immediate fail-closed rejection.
			if matchResultCorrelation(record.binding, payload, result) != "" || !workspaceResultIsExact(result) {
				return logicalRequestSnapshot{}, artifactDisposition{}, true,
					fmt.Errorf("artifact receipt rejected: %s", receipt.mismatchReason)
			}
			if primaryFailure == nil {
				primaryFailure = &hotPathEndpointError{
					Status: http.StatusBadRequest, Type: "invalid_request_error",
					Message: "artifact continuation rejected: artifact receipt rejected: " + receipt.mismatchReason,
				}
			}
			continue
		}
	}
	if primaryFailure != nil && (lightFlows == nil || !lightFlows.has(record.requestID, record.ownerEdgeID)) {
		return logicalRequestSnapshot{}, artifactDisposition{}, true, fmt.Errorf("artifact receipt rejected: result contains an explicit error signal")
	}

	snap, err := coordinator.consumeContinuationByLineage(ownerEdgeID, principalRef, lineage)
	if err != nil {
		return logicalRequestSnapshot{}, artifactDisposition{}, true, err
	}
	for id := range record.pending {
		record.consumedIDs[id] = struct{}{}
	}
	record.consumedHashes[record.pendingHash] = struct{}{}
	record.pending = nil
	record.pendingHash = ""
	record.lineage = lineage.Committed
	if primaryFailure != nil {
		return snap, artifactDisposition{
			Kind: artifactDispositionLocalEligible, SelectorStageID: record.selectorStageID,
			PrimaryError: primaryFailure,
		}, true, nil
	}

	switch record.phase {
	case artifactPhasePreparePending:
		snap, err = coordinator.activateStage(record.requestID, record.ownerEdgeID, record.selectorStageID)
		if err != nil {
			return logicalRequestSnapshot{}, artifactDisposition{}, true, fmt.Errorf("resume artifact selector stage: %w", err)
		}
		record.phase = artifactPhasePairReady
		return snap, artifactDisposition{Kind: artifactDispositionResumeSelector, SelectorStageID: record.selectorStageID}, true, nil
	case artifactPhasePairPending:
		record.phase = artifactPhaseLocalEligible
		return snap, artifactDisposition{Kind: artifactDispositionLocalEligible, SelectorStageID: record.selectorStageID}, true, nil
	default:
		return logicalRequestSnapshot{}, artifactDisposition{}, true, fmt.Errorf("artifact frontier phase cannot consume results")
	}
}

func (s *artifactFrontierStore) matchRecordLocked(
	ownerEdgeID, principalRef, protocol string,
	lineage logicalRequestContinuationLineage,
) (*artifactFrontierRecord, bool, error) {
	var candidates []*artifactFrontierRecord
	for _, record := range s.records {
		pendingRelated := record.pending != nil && (record.pendingHash == lineage.IssuedCallHash || artifactIDsIntersect(record, lineage.ResultIDs) || record.lineage == lineage.Prefix)
		_, consumedHash := record.consumedHashes[lineage.IssuedCallHash]
		if pendingRelated || consumedHash || artifactConsumedIDsIntersect(record, lineage.ResultIDs) {
			candidates = append(candidates, record)
		}
	}
	if len(candidates) == 0 {
		return nil, false, nil
	}
	for _, record := range candidates {
		if _, replay := record.consumedHashes[lineage.IssuedCallHash]; replay {
			return nil, true, fmt.Errorf("artifact frontier replay rejected")
		}
	}
	for _, record := range candidates {
		if record.pendingHash != lineage.IssuedCallHash {
			continue
		}
		if record.ownerEdgeID != ownerEdgeID {
			return nil, true, errLogicalRequestOwnerMismatch
		}
		if record.principalRef != principalRef {
			return nil, true, errLogicalRequestPrincipal
		}
		if record.protocol != protocol || record.lineage != lineage.Prefix {
			return nil, true, errLogicalRequestLineage
		}
		return record, true, nil
	}
	for _, record := range candidates {
		if record.ownerEdgeID == ownerEdgeID && record.principalRef == principalRef && record.protocol == protocol && record.lineage == lineage.Prefix {
			return record, true, nil
		}
	}
	return nil, true, errLogicalRequestLineage
}

func artifactIDsIntersect(record *artifactFrontierRecord, ids []string) bool {
	for _, id := range ids {
		if record.pending[id] != nil {
			return true
		}
	}
	return false
}

func artifactConsumedIDsIntersect(record *artifactFrontierRecord, ids []string) bool {
	for _, id := range ids {
		if _, consumed := record.consumedIDs[id]; consumed {
			return true
		}
	}
	return false
}

func decodeChatWorkspaceResults(rawBody []byte) ([]workspaceResult, error) {
	var envelope struct {
		Messages []struct {
			Role       string          `json:"role"`
			ToolCallID string          `json:"tool_call_id"`
			Content    json.RawMessage `json:"content"`
		} `json:"messages"`
	}
	if err := json.Unmarshal(rawBody, &envelope); err != nil {
		return nil, fmt.Errorf("decode Chat artifact results: %w", err)
	}
	var reversed []workspaceResult
	for i := len(envelope.Messages) - 1; i >= 0; i-- {
		message := envelope.Messages[i]
		if message.Role != "tool" {
			break
		}
		body, err := workspaceResultBody(message.Content)
		if err != nil {
			return nil, fmt.Errorf("decode Chat tool result %q: %w", message.ToolCallID, err)
		}
		reversed = append(reversed, workspaceResult{callID: message.ToolCallID, status: "success", body: body})
	}
	results := make([]workspaceResult, len(reversed))
	for i := range reversed {
		results[len(reversed)-1-i] = reversed[i]
	}
	if len(results) == 0 {
		return nil, fmt.Errorf("Chat artifact continuation has no tool results")
	}
	return results, nil
}

func decodeAnthropicWorkspaceResults(rawBody []byte) ([]workspaceResult, error) {
	var envelope struct {
		Messages []struct {
			Role    string          `json:"role"`
			Content json.RawMessage `json:"content"`
		} `json:"messages"`
	}
	if err := json.Unmarshal(rawBody, &envelope); err != nil {
		return nil, fmt.Errorf("decode Messages artifact results: %w", err)
	}
	if len(envelope.Messages) == 0 || envelope.Messages[len(envelope.Messages)-1].Role != "user" {
		return nil, fmt.Errorf("Messages artifact continuation has no trailing user results")
	}
	var blocks []struct {
		Type      string          `json:"type"`
		ToolUseID string          `json:"tool_use_id"`
		Content   json.RawMessage `json:"content"`
		IsError   bool            `json:"is_error,omitempty"`
	}
	if err := json.Unmarshal(envelope.Messages[len(envelope.Messages)-1].Content, &blocks); err != nil {
		return nil, fmt.Errorf("decode Messages artifact result blocks: %w", err)
	}
	results := make([]workspaceResult, 0, len(blocks))
	for _, block := range blocks {
		if block.Type != "tool_result" {
			return nil, fmt.Errorf("Messages artifact result contains non-tool_result block")
		}
		body, err := workspaceResultBody(block.Content)
		if err != nil {
			return nil, fmt.Errorf("decode Messages tool result %q: %w", block.ToolUseID, err)
		}
		status := "success"
		if block.IsError {
			status = "error"
		}
		results = append(results, workspaceResult{callID: block.ToolUseID, status: status, body: body})
	}
	if len(results) == 0 {
		return nil, fmt.Errorf("Messages artifact continuation has no tool results")
	}
	return results, nil
}

func workspaceResultBody(raw json.RawMessage) (json.RawMessage, error) {
	trimmed := strings.TrimSpace(string(raw))
	if trimmed == "" || trimmed == "null" {
		return nil, nil
	}
	var text string
	if err := json.Unmarshal(raw, &text); err == nil {
		return json.RawMessage(strings.TrimSpace(text)), nil
	}
	var value any
	if err := json.Unmarshal(raw, &value); err != nil {
		return nil, err
	}
	return append(json.RawMessage(nil), raw...), nil
}

func decodeArtifactTools(protocol string, rawBody []byte) (any, error) {
	switch protocol {
	case "openai":
		var envelope struct {
			Tools []any `json:"tools"`
		}
		decoder := json.NewDecoder(strings.NewReader(string(rawBody)))
		decoder.UseNumber()
		if err := decoder.Decode(&envelope); err != nil {
			return nil, fmt.Errorf("decode Chat workspace tools: %w", err)
		}
		return envelope.Tools, nil
	case "anthropic":
		var envelope struct {
			Tools []anthropicTool `json:"tools"`
		}
		if err := json.Unmarshal(rawBody, &envelope); err != nil {
			return nil, fmt.Errorf("decode Messages workspace tools: %w", err)
		}
		return envelope.Tools, nil
	default:
		return nil, fmt.Errorf("unsupported artifact protocol %q", protocol)
	}
}