package responses

import (
	"bytes"
	"encoding/json"
	"net/http"
	"strings"
	"testing"

	"gitea.rutua.cn/kate522/CrossRelay/internal/chatcmpl"
)

// captureWriter records everything the converter writes.
type captureWriter struct {
	header  http.Header
	body    bytes.Buffer
	status  int
	flushes int
}

func newCaptureWriter() *captureWriter {
	return &captureWriter{header: http.Header{}}
}

func (c *captureWriter) Header() http.Header         { return c.header }
func (c *captureWriter) Write(b []byte) (int, error) { return c.body.Write(b) }
func (c *captureWriter) WriteHeader(status int)      { c.status = status }
func (c *captureWriter) Flush()                      { c.flushes++ }

type sseEvent struct {
	name string
	data map[string]any
}

func parseSSE(t *testing.T, data string) []sseEvent {
	t.Helper()
	var events []sseEvent
	for _, block := range strings.Split(strings.TrimSpace(data), "\n\n") {
		if block == "" {
			continue
		}
		var name string
		var payload string
		for _, line := range strings.Split(block, "\n") {
			switch {
			case strings.HasPrefix(line, "event: "):
				name = strings.TrimPrefix(line, "event: ")
			case strings.HasPrefix(line, "data: "):
				payload = strings.TrimPrefix(line, "data: ")
			}
		}
		var parsed map[string]any
		if err := json.Unmarshal([]byte(payload), &parsed); err != nil {
			t.Fatalf("event %s payload is not JSON: %v (%s)", name, err, payload)
		}
		events = append(events, sseEvent{name: name, data: parsed})
	}
	return events
}

func eventNames(events []sseEvent) []string {
	names := make([]string, len(events))
	for i, e := range events {
		names[i] = e.name
	}
	return names
}

func textChunk(text string) *chatcmpl.StreamChunk {
	return &chatcmpl.StreamChunk{Choices: []chatcmpl.ChunkChoice{{Delta: chatcmpl.Delta{Content: &text}}}}
}

func finishChunk(reason string, usage *chatcmpl.Usage) *chatcmpl.StreamChunk {
	return &chatcmpl.StreamChunk{
		Choices: []chatcmpl.ChunkChoice{{FinishReason: &reason}},
		Usage:   usage,
	}
}

func runConverter(t *testing.T, chunks []*chatcmpl.StreamChunk) []sseEvent {
	t.Helper()
	w := newCaptureWriter()
	conv := NewStreamConverter(w, "gpt-5-codex", 42)
	if err := conv.WriteStart(); err != nil {
		t.Fatalf("WriteStart: %v", err)
	}
	for _, c := range chunks {
		if err := conv.OnChunk(c); err != nil {
			t.Fatalf("OnChunk: %v", err)
		}
	}
	if err := conv.Finish(); err != nil {
		t.Fatalf("Finish: %v", err)
	}
	if w.status != http.StatusOK {
		t.Errorf("status = %d", w.status)
	}
	if ct := w.header.Get("Content-Type"); ct != "text/event-stream; charset=utf-8" {
		t.Errorf("content type = %q", ct)
	}
	return parseSSE(t, w.body.String())
}

func TestStreamTextOnly(t *testing.T) {
	events := runConverter(t, []*chatcmpl.StreamChunk{
		textChunk("Hello"),
		textChunk(", world"),
		finishChunk("stop", &chatcmpl.Usage{PromptTokens: 10, CompletionTokens: 3}),
	})
	wantNames := []string{
		"response.created",
		"response.in_progress",
		"response.output_item.added",
		"response.content_part.added",
		"response.output_text.delta",
		"response.output_text.delta",
		"response.output_text.done",
		"response.content_part.done",
		"response.output_item.done",
		"response.completed",
	}
	if got := eventNames(events); !equalStrings(got, wantNames) {
		t.Fatalf("events = %v, want %v", got, wantNames)
	}
	for i, e := range events {
		if seq, ok := e.data["sequence_number"].(float64); !ok || int(seq) != i+1 {
			t.Errorf("event %d (%s) sequence_number = %v, want %d", i, e.name, e.data["sequence_number"], i+1)
		}
	}
	created := events[0].data["response"].(map[string]any)
	if created["status"] != "in_progress" {
		t.Errorf("created status = %v", created["status"])
	}
	if created["model"] != "gpt-5-codex" {
		t.Errorf("created model = %v", created["model"])
	}
	added := events[2].data["item"].(map[string]any)
	if added["type"] != "message" || added["role"] != "assistant" {
		t.Errorf("added item = %v", added)
	}
	if events[4].data["delta"] != "Hello" || events[5].data["delta"] != ", world" {
		t.Errorf("deltas = %v, %v", events[4].data["delta"], events[5].data["delta"])
	}
	completed := events[9].data["response"].(map[string]any)
	if completed["status"] != "completed" {
		t.Errorf("completed status = %v", completed["status"])
	}
	if completed["output_text"] != "Hello, world" {
		t.Errorf("completed output_text = %v", completed["output_text"])
	}
	usage := completed["usage"].(map[string]any)
	if usage["input_tokens"].(float64) != 10 || usage["output_tokens"].(float64) != 3 {
		t.Errorf("completed usage = %v", usage)
	}
	output := completed["output"].([]any)
	if len(output) != 1 {
		t.Fatalf("completed output = %v", output)
	}
	msg := output[0].(map[string]any)
	content := msg["content"].([]any)
	part := content[0].(map[string]any)
	if part["type"] != "output_text" || part["text"] != "Hello, world" {
		t.Errorf("completed message content = %v", part)
	}
}

func TestStreamToolCall(t *testing.T) {
	events := runConverter(t, []*chatcmpl.StreamChunk{
		{Choices: []chatcmpl.ChunkChoice{{Delta: chatcmpl.Delta{ToolCalls: []chatcmpl.ToolCall{{
			Index: 0, ID: "call_1", Type: "function",
			Function: chatcmpl.ToolCallFunction{Name: "read_file"},
		}}}}}},
		{Choices: []chatcmpl.ChunkChoice{{Delta: chatcmpl.Delta{ToolCalls: []chatcmpl.ToolCall{{
			Index: 0, Function: chatcmpl.ToolCallFunction{Arguments: `{"path":`},
		}}}}}},
		{Choices: []chatcmpl.ChunkChoice{{Delta: chatcmpl.Delta{ToolCalls: []chatcmpl.ToolCall{{
			Index: 0, Function: chatcmpl.ToolCallFunction{Arguments: `"a.txt"}`},
		}}}}}},
		finishChunk("tool_calls", &chatcmpl.Usage{PromptTokens: 7, CompletionTokens: 5}),
	})
	wantNames := []string{
		"response.created",
		"response.in_progress",
		"response.output_item.added",
		"response.function_call_arguments.delta",
		"response.function_call_arguments.delta",
		"response.function_call_arguments.done",
		"response.output_item.done",
		"response.completed",
	}
	if got := eventNames(events); !equalStrings(got, wantNames) {
		t.Fatalf("events = %v, want %v", got, wantNames)
	}
	added := events[2].data["item"].(map[string]any)
	if added["type"] != "function_call" || added["call_id"] != "call_1" || added["name"] != "read_file" {
		t.Errorf("added item = %v", added)
	}
	if events[3].data["delta"] != `{"path":` || events[4].data["delta"] != `"a.txt"}` {
		t.Errorf("argument deltas = %v, %v", events[3].data["delta"], events[4].data["delta"])
	}
	if events[5].data["arguments"] != `{"path":"a.txt"}` {
		t.Errorf("arguments done = %v", events[5].data["arguments"])
	}
	for _, e := range events[2:7] {
		if e.data["output_index"].(float64) != 0 {
			t.Errorf("%s output_index = %v, want 0", e.name, e.data["output_index"])
		}
	}
	completed := events[7].data["response"].(map[string]any)
	output := completed["output"].([]any)
	call := output[0].(map[string]any)
	if call["call_id"] != "call_1" || call["arguments"] != `{"path":"a.txt"}` {
		t.Errorf("completed function_call = %v", call)
	}
}

func TestStreamParallelToolCalls(t *testing.T) {
	events := runConverter(t, []*chatcmpl.StreamChunk{
		{Choices: []chatcmpl.ChunkChoice{{Delta: chatcmpl.Delta{ToolCalls: []chatcmpl.ToolCall{{
			Index: 0, ID: "call_a", Type: "function",
			Function: chatcmpl.ToolCallFunction{Name: "tool_a"},
		}}}}}},
		{Choices: []chatcmpl.ChunkChoice{{Delta: chatcmpl.Delta{ToolCalls: []chatcmpl.ToolCall{{
			Index: 1, ID: "call_b", Type: "function",
			Function: chatcmpl.ToolCallFunction{Name: "tool_b", Arguments: `{}`},
		}}}}}},
		{Choices: []chatcmpl.ChunkChoice{{Delta: chatcmpl.Delta{ToolCalls: []chatcmpl.ToolCall{{
			Index: 0, Function: chatcmpl.ToolCallFunction{Arguments: `{"x":1}`},
		}}}}}},
		finishChunk("tool_calls", nil),
	})
	names := map[float64]string{}
	args := map[float64]string{}
	for _, e := range events {
		if e.name == "response.output_item.added" {
			idx := e.data["output_index"].(float64)
			names[idx] = e.data["item"].(map[string]any)["name"].(string)
		}
		if e.name == "response.function_call_arguments.delta" {
			idx := e.data["output_index"].(float64)
			args[idx] += e.data["delta"].(string)
		}
	}
	if len(names) != 2 {
		t.Fatalf("output_item.added count = %d, want 2 (%v)", len(names), names)
	}
	if names[0] != "tool_a" || names[1] != "tool_b" {
		t.Errorf("tool names by output index = %v", names)
	}
	if args[0] != `{"x":1}` || args[1] != `{}` {
		t.Errorf("interleaved args = %v", args)
	}
}

func TestStreamSynthesizesCallID(t *testing.T) {
	events := runConverter(t, []*chatcmpl.StreamChunk{
		{Choices: []chatcmpl.ChunkChoice{{Delta: chatcmpl.Delta{ToolCalls: []chatcmpl.ToolCall{{
			Index: 0, Type: "function",
			Function: chatcmpl.ToolCallFunction{Name: "shell"},
		}}}}}},
		finishChunk("tool_calls", nil),
	})
	added := events[2].data["item"].(map[string]any)
	callID, _ := added["call_id"].(string)
	if !strings.HasPrefix(callID, "call_") {
		t.Errorf("synthesized call_id = %q, want a call_ prefix", callID)
	}
}

func TestStreamLengthFinishIsIncomplete(t *testing.T) {
	events := runConverter(t, []*chatcmpl.StreamChunk{
		textChunk("cut"),
		finishChunk("length", nil),
	})
	completed := events[len(events)-1]
	if completed.name != "response.completed" {
		t.Fatalf("last event = %s", completed.name)
	}
	resp := completed.data["response"].(map[string]any)
	if resp["status"] != "incomplete" {
		t.Errorf("status = %v, want incomplete", resp["status"])
	}
	details, ok := resp["incomplete_details"].(map[string]any)
	if !ok || details["reason"] != "max_output_tokens" {
		t.Errorf("incomplete_details = %v", resp["incomplete_details"])
	}
}

func TestStreamEstimatedUsageWithoutUpstreamUsage(t *testing.T) {
	events := runConverter(t, []*chatcmpl.StreamChunk{
		textChunk("some text"),
		finishChunk("stop", nil),
	})
	completed := events[len(events)-1].data["response"].(map[string]any)
	usage := completed["usage"].(map[string]any)
	if usage["input_tokens"].(float64) != 42 {
		t.Errorf("input tokens = %v, want the 42 estimate", usage["input_tokens"])
	}
	if usage["output_tokens"].(float64) <= 0 {
		t.Errorf("output tokens = %v, want a positive estimate", usage["output_tokens"])
	}
}

func TestStreamEmptyUpstream(t *testing.T) {
	events := runConverter(t, nil)
	want := []string{"response.created", "response.in_progress", "response.completed"}
	if got := eventNames(events); !equalStrings(got, want) {
		t.Fatalf("events = %v, want %v", got, want)
	}
}

func TestStreamWriteError(t *testing.T) {
	w := newCaptureWriter()
	conv := NewStreamConverter(w, "gpt-5-codex", 1)
	if err := conv.WriteStart(); err != nil {
		t.Fatalf("WriteStart: %v", err)
	}
	conv.WriteError("api_error", "upstream exploded")
	events := parseSSE(t, w.body.String())
	last := events[len(events)-1]
	if last.name != "response.failed" {
		t.Fatalf("last event = %s, want response.failed", last.name)
	}
	resp := last.data["response"].(map[string]any)
	if resp["status"] != "failed" {
		t.Errorf("status = %v", resp["status"])
	}
	errObj := resp["error"].(map[string]any)
	if errObj["code"] != "api_error" || errObj["message"] != "upstream exploded" {
		t.Errorf("error = %v", errObj)
	}
}

func equalStrings(a, b []string) bool {
	if len(a) != len(b) {
		return false
	}
	for i := range a {
		if a[i] != b[i] {
			return false
		}
	}
	return true
}