package agent

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"strconv"
	"strings"
	"sync/atomic"
	"testing"
	"time"

	"reasonix/internal/event"
	"reasonix/internal/provider"
	"reasonix/internal/runtimepolicy"
	"reasonix/internal/tool"
	"reasonix/internal/workspacelease"
)

func TestParallelTasksToolIsReadOnly(t *testing.T) {
	p := &ParallelTasksTool{}
	if !p.ReadOnly() {
		t.Fatal("parallel_tasks must be read-only because spawned sub-agents receive only read-only tools")
	}
	if !p.PlanModeSafe() {
		t.Fatal("parallel_tasks must explicitly allow the planning phase")
	}
}

func TestParallelTasksSchemaKeepsDependencyOrderingHidden(t *testing.T) {
	schema := string((&ParallelTasksTool{}).Schema())
	if strings.Contains(schema, "depends_on") {
		t.Fatal("parallel_tasks schema should not expose depends_on by default; changing tool schema hurts prompt-cache stability")
	}
}

func TestParallelTasksValidatesAllTasksBeforeRuntimeLookup(t *testing.T) {
	tool := &ParallelTasksTool{}
	_, err := tool.Execute(context.Background(), json.RawMessage(`{
		"tasks": [
			{"prompt": "inspect the parser"},
			{"prompt": "   "}
		]
	}`))
	if err == nil {
		t.Fatal("Execute returned nil error for an empty later task")
	}
	if !strings.Contains(err.Error(), "task 2: prompt is required") {
		t.Fatalf("Execute error = %v, want task validation before runtime lookup", err)
	}
	if strings.Contains(err.Error(), "background jobs are not available") {
		t.Fatalf("Execute looked up background jobs before validating all tasks: %v", err)
	}
}

func TestParallelTasksRejectsHiddenDependencyFieldBeforeRuntimeLookup(t *testing.T) {
	tool := &ParallelTasksTool{}
	_, err := tool.Execute(context.Background(), json.RawMessage(`{
		"tasks": [
			{"prompt": "first", "depends_on": [1]},
			{"prompt": "second"}
		]
	}`))
	if err == nil {
		t.Fatal("Execute returned nil error for a hidden dependency field")
	}
	if !strings.Contains(err.Error(), "depends_on") {
		t.Fatalf("Execute error = %v, want hidden dependency field rejection", err)
	}
	if strings.Contains(err.Error(), "background jobs are not available") {
		t.Fatalf("Execute looked up background jobs before rejecting hidden dependencies: %v", err)
	}
}

func TestParallelTasksRejectsUnboundedBatchBeforeRuntimeLookup(t *testing.T) {
	tasks := make([]parallelTaskItem, parallelTasksMaxTasks+1)
	for i := range tasks {
		tasks[i].Prompt = "inspect"
	}
	args, err := json.Marshal(map[string]any{"tasks": tasks})
	if err != nil {
		t.Fatalf("Marshal: %v", err)
	}

	_, err = (&ParallelTasksTool{}).Execute(context.Background(), args)
	if err == nil {
		t.Fatal("Execute returned nil error for an oversized batch")
	}
	if !strings.Contains(err.Error(), "at most 64 tasks") {
		t.Fatalf("Execute error = %v, want bounded-task rejection", err)
	}
	if strings.Contains(err.Error(), "not configured") {
		t.Fatalf("Execute looked up runtime before enforcing the batch cap: %v", err)
	}
}

func TestParallelTasksForegroundCompletesAndClosesWorkers(t *testing.T) {
	task := newTestTaskTool(t, parallelStaticProvider{}, tool.NewRegistry(), "sys", "", "", nil)
	parallel := NewParallelTasksTool(task, tool.NewRegistry())
	ctx := withCallContext(context.Background(), "parallel-call", event.Discard, nil, false)

	done := make(chan error, 1)
	go func() {
		out, err := parallel.Execute(ctx, json.RawMessage(`{
			"tasks": [
				{"prompt": "first"},
				{"prompt": "second"}
			]
		}`))
		if err != nil {
			done <- err
			return
		}
		if !strings.Contains(out, "Completed 2 parallel tasks") {
			done <- stringsError("missing aggregate output: " + out)
			return
		}
		done <- nil
	}()

	select {
	case err := <-done:
		if err != nil {
			t.Fatal(err)
		}
	case <-time.After(2 * time.Second):
		t.Fatal("parallel_tasks foreground execution did not return; workers likely waited on spawnCh forever")
	}
}

func TestParallelTasksLongResultsStayIndependentlyRetrievable(t *testing.T) {
	workspace := t.TempDir()
	store := NewSubagentStore(t.TempDir())
	task := NewTaskTool(parallelLongResultProvider{}, nil, tool.NewRegistry(), 20, 0, 0, 0, 0, 0, 0, 0.0, "", "sys", nil, 0, "", "", nil).
		WithTranscripts(store, workspace, "base-model", "base-effort")
	parallel := NewParallelTasksTool(task, tool.NewRegistry())
	ctx := WithParentSession(withCallContext(context.Background(), "parallel-call", event.Discard, nil, false), "parent-session")

	out, err := parallel.Execute(ctx, json.RawMessage(`{"tasks":[{"prompt":"first report"},{"prompt":"second report"}]}`))
	if err != nil {
		t.Fatalf("Execute: %v", err)
	}
	if len(out) > subagentAggregateBudgetBytes {
		t.Fatalf("aggregate bytes = %d, want <= %d", len(out), subagentAggregateBudgetBytes)
	}
	if _, notice := truncateToolOutput(out); notice != "" {
		t.Fatalf("bounded aggregate still hit the generic truncator: %s", notice)
	}
	if strings.Count(out, "Subagent reference: sa_") != 2 {
		t.Fatalf("aggregate did not preserve every child ref:\n%s", out)
	}
	if !strings.Contains(out, "preview truncated; read the full result") {
		t.Fatalf("aggregate did not explain lossless retrieval:\n%s", out)
	}

	refs := subagentRefsFromText(out)
	if len(refs) != 2 {
		t.Fatalf("refs = %v, want 2", refs)
	}
	reader := NewSubagentResultTool(task)
	for i, ref := range refs {
		page, readErr := reader.Execute(ctx, json.RawMessage(fmt.Sprintf(`{"ref":%q,"limit_bytes":24576}`, ref)))
		if readErr != nil {
			t.Fatalf("read result %d: %v", i+1, readErr)
		}
		wantBegin, wantEnd := "FIRST-BEGIN", "FIRST-END"
		if i == 1 {
			wantBegin, wantEnd = "SECOND-BEGIN", "SECOND-END"
		}
		if !strings.Contains(page, wantBegin) || !strings.Contains(page, wantEnd) || !strings.Contains(page, "End of subagent result") {
			t.Fatalf("read result %d was not complete: head=%q tail=%q", i+1, page[:minInt(120, len(page))], page[max(0, len(page)-120):])
		}
	}

	otherCtx := WithParentSession(context.Background(), "other-session")
	if _, err := reader.Execute(otherCtx, json.RawMessage(fmt.Sprintf(`{"ref":%q}`, refs[0]))); err == nil {
		t.Fatal("reader accepted a result from an unrelated parent session")
	}
}

func TestParallelTasksInjectsWorkspaceContextIntoChildren(t *testing.T) {
	workspace := t.TempDir()
	task := NewTaskTool(promptRoutingProvider{}, nil, tool.NewRegistry(), 20, 0, 0, 0, 0, 0, 0, 0.0, "", "sys", nil, 0, "", "", nil).
		WithTranscripts(NewSubagentStore(t.TempDir()), workspace, "base-model", "base-effort")
	parallel := NewParallelTasksTool(task, tool.NewRegistry())
	ctx := withCallContext(context.Background(), "parallel-call", event.Discard, nil, false)

	out, err := parallel.Execute(ctx, json.RawMessage(`{"tasks":[{"prompt":"inspect one"},{"prompt":"inspect two"}]}`))
	if err != nil {
		t.Fatalf("Execute: %v", err)
	}
	if !strings.Contains(out, "Current workspace: "+strconv.Quote(workspace)) ||
		!strings.Contains(out, `prefer "." or relative paths`) ||
		!strings.Contains(out, "inspect one") ||
		!strings.Contains(out, "inspect two") {
		t.Fatalf("parallel output = %q, want child workspace context and prompt", out)
	}
}

// TestParallelTasksDeliveryClassifiesPristinePrompt pins the trusted
// classifier channel on the parallel_tasks path: delivery intent must be
// judged from the child's pristine prompt, not the workspace-wrapped text.
// The wrapper is long enough that the IsTask length fallback classifies it as
// a task; without ClassifierTaskText a plain conversational child ("Who are
// you?") would be required to produce work receipts it has no reason to earn
// and would exhaust final-answer readiness instead of answering.
func TestParallelTasksDeliveryClassifiesPristinePrompt(t *testing.T) {
	workspace := t.TempDir()
	task := NewTaskTool(promptRoutingProvider{}, nil, tool.NewRegistry(), 20, 0, 0, 0, 0, 0, 0, 0.0, "", "sys", nil, 0, "", "", nil).
		WithTranscripts(NewSubagentStore(t.TempDir()), workspace, "base-model", "base-effort")
	parallel := NewParallelTasksTool(task, tool.NewRegistry())
	ctx := withCallContext(context.Background(), "parallel-call", event.Discard, nil, false)

	out, err := parallel.Execute(ctx, json.RawMessage(`{"tasks":[{"prompt":"Who are you?"},{"prompt":"Nice to meet you"}]}`))
	if err != nil {
		t.Fatalf("Execute: %v", err)
	}
	if strings.Contains(out, "readiness") {
		t.Fatalf("delivery readiness leaked into a conversational parallel child: %q", out)
	}
	// The echo provider replays the child's full user turn; both children must
	// have answered (their prompts echo back with the trailing " ok").
	if !strings.Contains(out, "Who are you?") || !strings.Contains(out, "Nice to meet you") || strings.Count(out, " ok") < 2 {
		t.Fatalf("parallel output = %q, want both children's answers", out)
	}
}

// TestParallelTasksInheritLanguagePreferencesFromContext pins parallel children
// to the same transient language injection the task tool applies: both the
// response- and reasoning-language blocks must reach each child's user turn.
func TestParallelTasksInheritLanguagePreferencesFromContext(t *testing.T) {
	task := newTestTaskTool(t, promptRoutingProvider{}, tool.NewRegistry(), "sys", "", "", nil)
	parallel := NewParallelTasksTool(task, tool.NewRegistry())
	ctx := withCallContext(context.Background(), "parallel-call", event.Discard, nil, false)
	ctx = WithResponseLanguagePreference(ctx, "zh")
	ctx = WithReasoningLanguagePreference(ctx, "zh")

	out, err := parallel.Execute(ctx, json.RawMessage(`{"tasks":[{"prompt":"inspect one"},{"prompt":"inspect two"}]}`))
	if err != nil {
		t.Fatalf("Execute: %v", err)
	}
	if !strings.Contains(out, "<response-language>") || !strings.Contains(out, "<reasoning-language>") {
		t.Fatalf("parallel output = %q, want response/reasoning language blocks injected into child prompts", out)
	}
}

func TestParallelTasksDoesNotExposeWriterToolsToChildren(t *testing.T) {
	var writerCalls int32
	parentReg := tool.NewRegistry()
	parentReg.Add(fakeTool{name: "write_file", readOnly: false, calls: &writerCalls})
	task := newTestTaskTool(t, writerCallingProvider{}, parentReg, "sys", "", "", nil)
	parallel := NewParallelTasksTool(task, parentReg)
	ctx := withCallContext(context.Background(), "parallel-call", event.Discard, nil, false)

	out, err := parallel.Execute(ctx, json.RawMessage(`{
		"tasks": [
			{"prompt": "try writer one"},
			{"prompt": "try writer two"}
		]
	}`))
	if err != nil {
		t.Fatalf("Execute returned error: %v\n%s", err, out)
	}
	if got := atomic.LoadInt32(&writerCalls); got != 0 {
		t.Fatalf("writer tool was exposed to read-only sub-agents and called %d times", got)
	}
	if !strings.Contains(out, "Completed 2 parallel tasks") {
		t.Fatalf("missing aggregate output: %s", out)
	}
}

func TestParallelTasksBlocksWriterResolvedThroughReadOnlyProxy(t *testing.T) {
	var writerCalls int32
	parentReg := tool.NewRegistry()
	target := parallelResolvedWriterTarget{calls: &writerCalls}
	parentReg.Add(readOnlyBoundaryProxy{resolved: tool.ResolvedCall{
		ProxyAction: "call",
		TargetName:  target.Name(),
		Target:      target,
		ReadOnly:    false,
		Args:        json.RawMessage(`{}`),
	}})
	task := newTestTaskTool(t, proxyWriterCallingProvider{}, parentReg, "sys", "", "", nil)
	parallel := NewParallelTasksTool(task, parentReg)
	ctx := withCallContext(context.Background(), "parallel-call", event.Discard, nil, false)

	out, err := parallel.Execute(ctx, json.RawMessage(`{
		"tasks": [
			{"prompt": "resolve writer one"},
			{"prompt": "resolve writer two"}
		]
	}`))
	if err != nil {
		t.Fatalf("Execute returned error: %v\n%s", err, out)
	}
	if got := atomic.LoadInt32(&writerCalls); got != 0 {
		t.Fatalf("use_capability resolved writer executed %d times, want 0", got)
	}
	if !strings.Contains(out, "Completed 2 parallel tasks") {
		t.Fatalf("missing aggregate output: %s", out)
	}
}

func TestParallelTasksCancelReturnsPartialAggregate(t *testing.T) {
	task := newTestTaskTool(t, promptRoutingProvider{}, tool.NewRegistry(), "sys", "", "", nil)
	parallel := NewParallelTasksTool(task, tool.NewRegistry())

	ctx, cancel := context.WithCancel(withCallContext(context.Background(), "parallel-call", event.Discard, nil, false))
	defer cancel()
	done := make(chan struct {
		out string
		err error
	}, 1)
	go func() {
		out, err := parallel.Execute(ctx, json.RawMessage(`{
			"tasks": [
				{"prompt": "done child"},
				{"prompt": "stuck child"}
			]
		}`))
		done <- struct {
			out string
			err error
		}{out: out, err: err}
	}()

	time.Sleep(100 * time.Millisecond)
	cancel()

	select {
	case got := <-done:
		if !errors.Is(got.err, context.Canceled) {
			t.Fatalf("Execute error = %v, want context cancellation", got.err)
		}
		if strings.Contains(got.out, "Completed 2 parallel tasks") {
			t.Fatalf("cancelled aggregate reported full completion:\n%s", got.out)
		}
		if !strings.Contains(got.out, "done child") || !strings.Contains(got.out, "ok") {
			t.Fatalf("cancelled aggregate lost completed child output:\n%s", got.out)
		}
		if !strings.Contains(strings.ToLower(got.out), "cancelled") {
			t.Fatalf("cancelled aggregate did not mark unfinished child:\n%s", got.out)
		}
	case <-time.After(500 * time.Millisecond):
		t.Fatal("parallel_tasks did not return promptly after cancellation")
	}
}

type parallelStaticProvider struct{}

func (parallelStaticProvider) Name() string { return "parallel-static" }

func (parallelStaticProvider) Stream(context.Context, provider.Request) (<-chan provider.Chunk, error) {
	ch := make(chan provider.Chunk, 2)
	ch <- provider.Chunk{Type: provider.ChunkText, Text: "ok"}
	ch <- provider.Chunk{Type: provider.ChunkDone}
	close(ch)
	return ch, nil
}

type parallelLongResultProvider struct{}

func (parallelLongResultProvider) Name() string { return "parallel-long-result" }

func (parallelLongResultProvider) Stream(_ context.Context, req provider.Request) (<-chan provider.Chunk, error) {
	begin, end, fill := "FIRST-BEGIN", "FIRST-END", "a"
	if strings.Contains(lastUser(req), "second report") {
		begin, end, fill = "SECOND-BEGIN", "SECOND-END", "b"
	}
	ch := make(chan provider.Chunk, 2)
	ch <- provider.Chunk{Type: provider.ChunkText, Text: begin + "\n" + strings.Repeat(fill, 20*1024) + "\n" + end}
	ch <- provider.Chunk{Type: provider.ChunkDone}
	close(ch)
	return ch, nil
}

func subagentRefsFromText(text string) []string {
	var refs []string
	for line := range strings.SplitSeq(text, "\n") {
		if after, ok := strings.CutPrefix(line, "Subagent reference: "); ok {
			refs = append(refs, strings.TrimSpace(after))
		}
	}
	return refs
}

type promptRoutingProvider struct{}

func (promptRoutingProvider) Name() string { return "prompt-routing" }

func (promptRoutingProvider) Stream(_ context.Context, req provider.Request) (<-chan provider.Chunk, error) {
	if strings.Contains(lastUser(req), "stuck") {
		return make(chan provider.Chunk), nil
	}
	ch := make(chan provider.Chunk, 2)
	ch <- provider.Chunk{Type: provider.ChunkText, Text: lastUser(req) + " ok"}
	ch <- provider.Chunk{Type: provider.ChunkDone}
	close(ch)
	return ch, nil
}

type writerCallingProvider struct{}

func (writerCallingProvider) Name() string { return "writer-calling" }

func (writerCallingProvider) Stream(_ context.Context, req provider.Request) (<-chan provider.Chunk, error) {
	ch := make(chan provider.Chunk, 2)
	if !hasToolResult(req, "write_file") {
		ch <- toolCallChunk("write-1", "write_file", `{"path":"x","content":"y"}`)
		ch <- provider.Chunk{Type: provider.ChunkDone}
		close(ch)
		return ch, nil
	}
	ch <- provider.Chunk{Type: provider.ChunkText, Text: "writer unavailable"}
	ch <- provider.Chunk{Type: provider.ChunkDone}
	close(ch)
	return ch, nil
}

type proxyWriterCallingProvider struct{}

func (proxyWriterCallingProvider) Name() string { return "proxy-writer-calling" }

func (proxyWriterCallingProvider) Stream(_ context.Context, req provider.Request) (<-chan provider.Chunk, error) {
	ch := make(chan provider.Chunk, 2)
	if !hasToolResult(req, "use_capability") {
		ch <- toolCallChunk("proxy-write-1", "use_capability", `{"action":"call","capability_id":"mcp-tool:test/write","arguments":{}}`)
		ch <- provider.Chunk{Type: provider.ChunkDone}
		close(ch)
		return ch, nil
	}
	ch <- provider.Chunk{Type: provider.ChunkText, Text: "writer blocked"}
	ch <- provider.Chunk{Type: provider.ChunkDone}
	close(ch)
	return ch, nil
}

type parallelResolvedWriterTarget struct {
	calls *int32
}

func (parallelResolvedWriterTarget) Name() string        { return "mcp__test__write" }
func (parallelResolvedWriterTarget) Description() string { return "" }
func (parallelResolvedWriterTarget) Schema() json.RawMessage {
	return json.RawMessage(`{"type":"object"}`)
}
func (parallelResolvedWriterTarget) ReadOnly() bool { return false }
func (t parallelResolvedWriterTarget) Execute(context.Context, json.RawMessage) (string, error) {
	atomic.AddInt32(t.calls, 1)
	return "writer executed", nil
}

func hasToolResult(req provider.Request, name string) bool {
	for _, m := range req.Messages {
		if m.Role == provider.RoleTool && m.Name == name {
			return true
		}
	}
	return false
}

type stringsError string

func (e stringsError) Error() string { return string(e) }

// TestChildMaxStepsSharedDefault pins the single step-budget rule shared by
// task, read_only_task, and parallel_tasks children: explicit request wins,
// a finite parent yields half its budget (min 5), an unbounded parent yields
// an unbounded child. parallel_tasks used to hardcode 20 instead.
func TestChildMaxStepsSharedDefault(t *testing.T) {
	cases := []struct {
		name      string
		parent    int
		requested int
		want      int
	}{
		{"explicit request wins", 30, 7, 7},
		{"finite parent halves", 30, 0, 15},
		{"half is floored at 5", 8, 0, 5},
		{"unbounded parent stays unbounded", 0, 0, 0},
	}
	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			task := &TaskTool{maxSteps: tc.parent}
			if got := task.childMaxSteps(tc.requested); got != tc.want {
				t.Fatalf("childMaxSteps(parent=%d, requested=%d) = %d, want %d", tc.parent, tc.requested, got, tc.want)
			}
		})
	}
}

func TestTaskToolPropagatesInheritedExecutionToSubagents(t *testing.T) {
	parent := runtimepolicy.InheritedExecutionContext{
		Constraints:  runtimepolicy.Constraints{ForbidMutation: true},
		PlanReadOnly: true,
		GoalScopeID:  "goal-1",
	}
	task := &TaskTool{}
	opts := task.subagentOptions(runtimepolicy.WithInherited(context.Background(), parent), 0, nil, 0, 1, "", nil)
	if opts.InheritedExecution == nil {
		t.Fatal("sub-agent options did not inherit parent execution context")
	}
	if !opts.InheritedExecution.PlanReadOnly || !opts.InheritedExecution.Constraints.ForbidMutation {
		t.Fatalf("inherited execution = %+v", opts.InheritedExecution)
	}
	if opts.InheritedExecution.GoalScopeID != "goal-1" {
		t.Fatalf("inherited goal scope = %q", opts.InheritedExecution.GoalScopeID)
	}
}

func TestTaskToolSharesWorkspaceLeaseWithSubagents(t *testing.T) {
	owner, err := workspacelease.New(t.TempDir(), t.TempDir(), nil)
	if err != nil {
		t.Fatalf("New workspace lease: %v", err)
	}
	task := (&TaskTool{}).WithWorkspaceLease(owner)
	opts := task.subagentOptions(context.Background(), 0, nil, 0, 1, "", nil)
	if opts.WorkspaceLease != owner {
		t.Fatal("sub-agent options did not share the parent's workspace lease owner")
	}
}

func TestTaskToolPropagatesWorkspaceRootToSubagents(t *testing.T) {
	root := t.TempDir()
	task := &TaskTool{workspaceRoot: root}
	opts := task.subagentOptions(context.Background(), 0, nil, 0, 1, "", nil)
	if opts.WriteWorkspaceRoot != root {
		t.Fatalf("sub-agent workspace root = %q, want %q", opts.WriteWorkspaceRoot, root)
	}
}

func TestSubagentRecoveryTaskIDIsStableAndIsolated(t *testing.T) {
	ctx := WithToolCallContext(context.Background(), "call-17", event.Discard, nil, false)
	if got := subagentRecoveryTaskID(ctx, ""); got != "subagent:call-17" {
		t.Fatalf("call-scoped recovery task id = %q", got)
	}
	if got := subagentRecoveryTaskID(ctx, "ref-abc"); got != "subagent:ref-abc" {
		t.Fatalf("transcript-scoped recovery task id = %q", got)
	}
}