package agent

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"strings"
	"testing"

	"gitea.stevedudenhoeffer.com/steve/majordomo/llm"
	"gitea.stevedudenhoeffer.com/steve/majordomo/provider/fake"
)

func newModel(t *testing.T, fp *fake.Provider) llm.Model {
	t.Helper()
	m, err := fp.Model("test-model")
	if err != nil {
		t.Fatalf("Model: %v", err)
	}
	return m
}

// toolCallReply scripts an assistant response requesting one tool call.
func toolCallReply(id, name, args string) fake.Step {
	return fake.ReplyWith(llm.Response{
		ToolCalls:    []llm.ToolCall{{ID: id, Name: name, Arguments: json.RawMessage(args)}},
		FinishReason: llm.FinishToolCalls,
		Usage:        llm.Usage{InputTokens: 10, OutputTokens: 5},
	})
}

func adderToolbox(t *testing.T) *llm.Toolbox {
	t.Helper()
	return llm.NewToolbox("math", llm.Tool{
		Name:        "add",
		Description: "Add two integers",
		Parameters:  json.RawMessage(`{"type":"object","properties":{"a":{"type":"integer"},"b":{"type":"integer"}},"required":["a","b"]}`),
		Handler: func(_ context.Context, args json.RawMessage) (any, error) {
			var p struct{ A, B int }
			if err := json.Unmarshal(args, &p); err != nil {
				return nil, err
			}
			return map[string]int{"sum": p.A + p.B}, nil
		},
	})
}

func TestRunWithoutTools(t *testing.T) {
	fp := fake.New("fp")
	fp.Enqueue("test-model", fake.Reply("direct answer"))

	a := New(newModel(t, fp), "You are terse.")
	res, err := a.Run(context.Background(), "question?")
	if err != nil {
		t.Fatalf("Run: %v", err)
	}
	if res.Output != "direct answer" {
		t.Errorf("output = %q", res.Output)
	}
	if len(res.Steps) != 1 {
		t.Errorf("steps = %d", len(res.Steps))
	}
	// The system prompt reached the model.
	calls := fp.Calls()
	if calls[0].Request.System != "You are terse." {
		t.Errorf("system = %q", calls[0].Request.System)
	}
}

func TestRunToolLoop(t *testing.T) {
	fp := fake.New("fp")
	fp.Enqueue("test-model",
		toolCallReply("c1", "add", `{"a":2,"b":3}`),
		fake.Reply("the sum is 5"),
	)

	a := New(newModel(t, fp), "do math", WithToolbox(adderToolbox(t)))
	res, err := a.Run(context.Background(), "2+3?")
	if err != nil {
		t.Fatalf("Run: %v", err)
	}
	if res.Output != "the sum is 5" {
		t.Errorf("output = %q", res.Output)
	}
	if len(res.Steps) != 2 {
		t.Fatalf("steps = %d, want 2", len(res.Steps))
	}
	if res.Usage.InputTokens != 11 || res.Usage.OutputTokens != 6 {
		t.Errorf("usage = %+v (must sum both steps)", res.Usage)
	}

	// The tool executed and its result went back to the model.
	step1 := res.Steps[0]
	if len(step1.Results) != 1 || step1.Results[0].IsError {
		t.Fatalf("step 1 results = %+v", step1.Results)
	}
	if !strings.Contains(step1.Results[0].Content, `"sum":5`) {
		t.Errorf("tool result = %q", step1.Results[0].Content)
	}

	// Second model call must carry the tool transcript: user, assistant
	// (with the call), tool results.
	second := fp.Calls()[1].Request
	if len(second.Messages) != 3 {
		t.Fatalf("second request messages = %d, want 3", len(second.Messages))
	}
	if second.Messages[1].Role != llm.RoleAssistant || len(second.Messages[1].ToolCalls) != 1 {
		t.Errorf("assistant turn = %+v", second.Messages[1])
	}
	toolMsg := second.Messages[2]
	if toolMsg.Role != llm.RoleTool || toolMsg.ToolResults[0].ID != "c1" {
		t.Errorf("tool turn = %+v", toolMsg)
	}

	// The tools were offered on every step.
	for i, c := range fp.Calls() {
		if len(c.Request.Tools) != 1 || c.Request.Tools[0].Name != "add" {
			t.Errorf("call %d tools = %+v", i, c.Request.Tools)
		}
	}

	// Result.Messages is the full transcript.
	if len(res.Messages) != 4 {
		t.Errorf("transcript = %d messages, want 4", len(res.Messages))
	}
}

func TestRunUnknownToolContinues(t *testing.T) {
	fp := fake.New("fp")
	fp.Enqueue("test-model",
		toolCallReply("c1", "nonexistent", `{}`),
		fake.Reply("recovered"),
	)

	a := New(newModel(t, fp), "", WithToolbox(adderToolbox(t)))
	res, err := a.Run(context.Background(), "go")
	if err != nil {
		t.Fatalf("Run: %v", err)
	}
	if res.Output != "recovered" {
		t.Errorf("output = %q", res.Output)
	}
	r := res.Steps[0].Results[0]
	if !r.IsError || !strings.Contains(r.Content, "nonexistent") {
		t.Errorf("unknown-tool result = %+v", r)
	}
}

func TestRunPanickingToolContinues(t *testing.T) {
	fp := fake.New("fp")
	fp.Enqueue("test-model",
		toolCallReply("c1", "bomb", `{}`),
		fake.Reply("survived"),
	)
	bomb := llm.NewToolbox("danger", llm.Tool{
		Name:    "bomb",
		Handler: func(context.Context, json.RawMessage) (any, error) { panic("boom") },
	})

	a := New(newModel(t, fp), "", WithToolbox(bomb))
	res, err := a.Run(context.Background(), "go")
	if err != nil {
		t.Fatalf("Run: %v", err)
	}
	if res.Output != "survived" {
		t.Errorf("output = %q", res.Output)
	}
	r := res.Steps[0].Results[0]
	if !r.IsError || !strings.Contains(r.Content, "boom") {
		t.Errorf("panic result = %+v", r)
	}
}

func TestRunMaxSteps(t *testing.T) {
	fp := fake.New("fp", fake.WithDefault(func(string, llm.Request) fake.Step {
		return toolCallReply("c", "add", `{"a":1,"b":1}`)
	}))

	a := New(newModel(t, fp), "", WithToolbox(adderToolbox(t)), WithMaxSteps(3))
	res, err := a.Run(context.Background(), "loop forever")
	if !errors.Is(err, ErrMaxSteps) {
		t.Fatalf("err = %v, want ErrMaxSteps", err)
	}
	if res == nil || len(res.Steps) != 3 {
		t.Fatalf("result = %+v, want 3 recorded steps", res)
	}
	if len(res.Messages) == 0 {
		t.Error("transcript must be preserved on ErrMaxSteps")
	}
}

func TestDuplicateToolNamesFailLoudly(t *testing.T) {
	fp := fake.New("fp")
	box1 := llm.NewToolbox("a", llm.Tool{Name: "dup"})
	box2 := llm.NewToolbox("b", llm.Tool{Name: "dup"})

	a := New(newModel(t, fp), "", WithToolbox(box1), WithToolbox(box2))
	_, err := a.Run(context.Background(), "go")
	if err == nil || !strings.Contains(err.Error(), `duplicate tool "dup"`) {
		t.Errorf("err = %v, want duplicate-tool error", err)
	}
}

func TestRunWithHistory(t *testing.T) {
	fp := fake.New("fp")
	fp.Enqueue("test-model", fake.Reply("continued"))

	history := []llm.Message{
		llm.UserText("first question"),
		llm.AssistantText("first answer"),
	}
	a := New(newModel(t, fp), "")
	res, err := a.Run(context.Background(), "follow-up", WithHistory(history))
	if err != nil {
		t.Fatalf("Run: %v", err)
	}
	got := fp.Calls()[0].Request.Messages
	if len(got) != 3 || got[0].Text() != "first question" || got[2].Text() != "follow-up" {
		t.Errorf("messages = %+v", got)
	}
	if len(res.Messages) != 4 {
		t.Errorf("transcript = %d, want history+input+answer", len(res.Messages))
	}
}

func TestStepObservers(t *testing.T) {
	fp := fake.New("fp")
	fp.Enqueue("test-model",
		toolCallReply("c1", "add", `{"a":1,"b":2}`),
		fake.Reply("3"),
	)

	var agentSteps, runSteps []int
	a := New(newModel(t, fp), "",
		WithToolbox(adderToolbox(t)),
		WithStepObserver(func(s Step) { agentSteps = append(agentSteps, s.Index) }),
	)
	_, err := a.Run(context.Background(), "1+2?",
		OnStep(func(s Step) { runSteps = append(runSteps, s.Index) }),
	)
	if err != nil {
		t.Fatalf("Run: %v", err)
	}
	if fmt.Sprint(agentSteps) != "[0 1]" || fmt.Sprint(runSteps) != "[0 1]" {
		t.Errorf("agentSteps=%v runSteps=%v", agentSteps, runSteps)
	}
}

func TestObserverPanicIsSwallowed(t *testing.T) {
	fp := fake.New("fp")
	fp.Enqueue("test-model", fake.Reply("fine"))

	a := New(newModel(t, fp), "", WithStepObserver(func(Step) { panic("ui bug") }))
	res, err := a.Run(context.Background(), "go")
	if err != nil || res.Output != "fine" {
		t.Errorf("res=%+v err=%v — observer panic must not kill the run", res, err)
	}
}

func TestSkillComposition(t *testing.T) {
	fp := fake.New("fp")
	fp.Enqueue("test-model", fake.Reply("ok"))

	sk := stubSkill{
		name:         "haiku",
		instructions: "Answer in haiku.",
		tools: llm.NewToolbox("haiku-tools", llm.Tool{
			Name:    "count_syllables",
			Handler: func(context.Context, json.RawMessage) (any, error) { return 5, nil },
		}),
	}
	a := New(newModel(t, fp), "Base prompt.", WithSkill(sk))
	if _, err := a.Run(context.Background(), "hello"); err != nil {
		t.Fatalf("Run: %v", err)
	}

	req := fp.Calls()[0].Request
	if req.System != "Base prompt.\n\nAnswer in haiku." {
		t.Errorf("system = %q", req.System)
	}
	if len(req.Tools) != 1 || req.Tools[0].Name != "count_syllables" {
		t.Errorf("tools = %+v", req.Tools)
	}
}

func TestAddSkillOnDemand(t *testing.T) {
	fp := fake.New("fp")
	fp.Enqueue("test-model", fake.Reply("a"), fake.Reply("b"))

	a := New(newModel(t, fp), "Base.")
	if _, err := a.Run(context.Background(), "one"); err != nil {
		t.Fatalf("Run: %v", err)
	}
	a.AddSkill(stubSkill{name: "later", instructions: "Later skill."})
	if _, err := a.Run(context.Background(), "two"); err != nil {
		t.Fatalf("Run: %v", err)
	}

	calls := fp.Calls()
	if calls[0].Request.System != "Base." {
		t.Errorf("first system = %q", calls[0].Request.System)
	}
	if calls[1].Request.System != "Base.\n\nLater skill." {
		t.Errorf("second system = %q", calls[1].Request.System)
	}
}

func TestRunErrorPreservesTranscript(t *testing.T) {
	fp := fake.New("fp")
	fp.Enqueue("test-model", fake.Fail(errors.New("model down")))

	a := New(newModel(t, fp), "")
	res, err := a.Run(context.Background(), "go")
	if err == nil || !strings.Contains(err.Error(), "model down") {
		t.Fatalf("err = %v", err)
	}
	if res == nil || len(res.Messages) != 1 {
		t.Errorf("result = %+v, want transcript with the input", res)
	}
}

func TestEmptyInputNeedsHistory(t *testing.T) {
	fp := fake.New("fp")
	a := New(newModel(t, fp), "")
	if _, err := a.Run(context.Background(), ""); err == nil {
		t.Error("empty input with no history must error")
	}
}

type stubSkill struct {
	name         string
	instructions string
	tools        *llm.Toolbox
}

func (s stubSkill) Name() string         { return s.name }
func (s stubSkill) Instructions() string { return s.instructions }
func (s stubSkill) Tools() *llm.Toolbox  { return s.tools }