package workflow

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

// ---------- helpers ----------

// anthropicJSONResponse returns a valid non-streaming Anthropic Messages API response body.
func anthropicJSONResponse(id, model, text, stopReason string, inputTok, outputTok int) string {
	return fmt.Sprintf(`{
		"id": %q,
		"type": "message",
		"role": "assistant",
		"model": %q,
		"content": [{"type":"text","text":%q}],
		"stop_reason": %q,
		"usage": {"input_tokens": %d, "output_tokens": %d}
	}`, id, model, text, stopReason, inputTok, outputTok)
}

// anthropicSSEStream builds an Anthropic-format SSE stream from the given text chunks.
func anthropicSSEStream(id, model string, chunks []string, stopReason string, inputTok, outputTok int) string {
	var sb strings.Builder

	// message_start
	sb.WriteString(fmt.Sprintf("event: message_start\ndata: {\"type\":\"message_start\",\"message\":{\"id\":%q,\"type\":\"message\",\"role\":\"assistant\",\"model\":%q,\"content\":[],\"stop_reason\":null,\"usage\":{\"input_tokens\":%d,\"output_tokens\":0}}}\n\n", id, model, inputTok))

	// content_block_start
	sb.WriteString("event: content_block_start\ndata: {\"type\":\"content_block_start\",\"index\":0,\"content_block\":{\"type\":\"text\",\"text\":\"\"}}\n\n")

	// content_block_delta for each chunk
	for _, chunk := range chunks {
		escaped, _ := json.Marshal(chunk) // properly escape the string
		sb.WriteString(fmt.Sprintf("event: content_block_delta\ndata: {\"type\":\"content_block_delta\",\"index\":0,\"delta\":{\"type\":\"text_delta\",\"text\":%s}}\n\n", string(escaped)))
	}

	// content_block_stop
	sb.WriteString("event: content_block_stop\ndata: {\"type\":\"content_block_stop\",\"index\":0}\n\n")

	// message_delta
	sb.WriteString(fmt.Sprintf("event: message_delta\ndata: {\"type\":\"message_delta\",\"delta\":{\"stop_reason\":%q},\"usage\":{\"output_tokens\":%d}}\n\n", stopReason, outputTok))

	// message_stop
	sb.WriteString("event: message_stop\ndata: {\"type\":\"message_stop\"}\n\n")

	return sb.String()
}

// ---------- non-streaming tests ----------

func TestAnthropicAdapter_NonStreaming_Basic(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// Verify request headers
		if r.Header.Get("x-api-key") != "test-key" {
			t.Errorf("expected x-api-key 'test-key', got %q", r.Header.Get("x-api-key"))
		}
		if r.Header.Get("anthropic-version") != "2023-06-01" {
			t.Errorf("expected anthropic-version '2023-06-01', got %q", r.Header.Get("anthropic-version"))
		}
		if r.Header.Get("Content-Type") != "application/json" {
			t.Errorf("expected Content-Type 'application/json', got %q", r.Header.Get("Content-Type"))
		}

		// Verify request body
		var req anthropicReq
		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
			t.Fatalf("failed to decode request: %v", err)
		}
		if req.Model != "claude-test" {
			t.Errorf("expected model 'claude-test', got %q", req.Model)
		}
		if req.Stream {
			t.Error("expected stream=false for non-streaming call")
		}

		w.Header().Set("Content-Type", "application/json")
		fmt.Fprint(w, anthropicJSONResponse("msg_123", "claude-test", "Hello world", "end_turn", 10, 5))
	}))
	defer server.Close()

	adapter := NewAnthropicAdapter(AnthropicConfig{
		APIKey:  "test-key",
		Model:   "claude-test",
		BaseURL: server.URL,
	})

	result, err := adapter.Call(context.Background(), map[string]interface{}{
		"messages": []interface{}{
			map[string]interface{}{"role": "user", "content": "hi"},
		},
	}, nil)
	if err != nil {
		t.Fatalf("Call() error: %v", err)
	}

	if result["content"] != "Hello world" {
		t.Errorf("content: got %q, want 'Hello world'", result["content"])
	}
	if result["model"] != "claude-test" {
		t.Errorf("model: got %q, want 'claude-test'", result["model"])
	}
	if result["finish_reason"] != "end_turn" {
		t.Errorf("finish_reason: got %q, want 'end_turn'", result["finish_reason"])
	}
	if result["response_id"] != "msg_123" {
		t.Errorf("response_id: got %q, want 'msg_123'", result["response_id"])
	}
	usage, ok := result["usage"].(map[string]interface{})
	if !ok {
		t.Fatal("missing usage")
	}
	if usage["prompt_tokens"] != 10 {
		t.Errorf("prompt_tokens: got %v, want 10", usage["prompt_tokens"])
	}
	if usage["completion_tokens"] != 5 {
		t.Errorf("completion_tokens: got %v, want 5", usage["completion_tokens"])
	}
	if usage["total_tokens"] != 15 {
		t.Errorf("total_tokens: got %v, want 15", usage["total_tokens"])
	}
}

func TestAnthropicAdapter_NonStreaming_SystemPrompt(t *testing.T) {
	var captured anthropicReq

	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		json.NewDecoder(r.Body).Decode(&captured)
		w.Header().Set("Content-Type", "application/json")
		fmt.Fprint(w, anthropicJSONResponse("msg_1", "claude-test", "ok", "end_turn", 5, 2))
	}))
	defer server.Close()

	adapter := NewAnthropicAdapter(AnthropicConfig{APIKey: "k", BaseURL: server.URL})

	_, err := adapter.Call(context.Background(), map[string]interface{}{
		"messages": []interface{}{
			map[string]interface{}{"role": "system", "content": "Be concise"},
			map[string]interface{}{"role": "user", "content": "hi"},
		},
	}, nil)
	if err != nil {
		t.Fatalf("Call() error: %v", err)
	}

	if captured.System != "Be concise" {
		t.Errorf("system: got %q, want 'Be concise'", captured.System)
	}
	if len(captured.Messages) != 1 {
		t.Fatalf("expected 1 message (user only), got %d", len(captured.Messages))
	}
	if captured.Messages[0].Role != "user" {
		t.Errorf("expected role 'user', got %q", captured.Messages[0].Role)
	}
}

func TestAnthropicAdapter_NonStreaming_PromptParam(t *testing.T) {
	var captured anthropicReq

	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		json.NewDecoder(r.Body).Decode(&captured)
		w.Header().Set("Content-Type", "application/json")
		fmt.Fprint(w, anthropicJSONResponse("msg_1", "claude-test", "ok", "end_turn", 5, 2))
	}))
	defer server.Close()

	adapter := NewAnthropicAdapter(AnthropicConfig{APIKey: "k", BaseURL: server.URL})

	_, err := adapter.Call(context.Background(), map[string]interface{}{
		"prompt": "hello there",
	}, nil)
	if err != nil {
		t.Fatalf("Call() error: %v", err)
	}

	if len(captured.Messages) != 1 || captured.Messages[0].Content != "hello there" {
		t.Errorf("expected single user message 'hello there', got %+v", captured.Messages)
	}
}

func TestAnthropicAdapter_NonStreaming_ModelOverride(t *testing.T) {
	var captured anthropicReq

	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		json.NewDecoder(r.Body).Decode(&captured)
		w.Header().Set("Content-Type", "application/json")
		fmt.Fprint(w, anthropicJSONResponse("msg_1", "claude-3-haiku", "ok", "end_turn", 5, 2))
	}))
	defer server.Close()

	adapter := NewAnthropicAdapter(AnthropicConfig{
		APIKey:  "k",
		Model:   "claude-default",
		BaseURL: server.URL,
	})

	_, err := adapter.Call(context.Background(), map[string]interface{}{
		"model":  "claude-3-haiku",
		"prompt": "hi",
	}, nil)
	if err != nil {
		t.Fatalf("Call() error: %v", err)
	}

	if captured.Model != "claude-3-haiku" {
		t.Errorf("expected model override 'claude-3-haiku', got %q", captured.Model)
	}
}

func TestAnthropicAdapter_NonStreaming_APIError(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusUnauthorized)
		fmt.Fprint(w, `{"error":{"type":"authentication_error","message":"invalid x-api-key"}}`)
	}))
	defer server.Close()

	adapter := NewAnthropicAdapter(AnthropicConfig{APIKey: "bad", BaseURL: server.URL})

	_, err := adapter.Call(context.Background(), map[string]interface{}{
		"prompt": "hi",
	}, nil)
	if err == nil {
		t.Fatal("expected error for 401 response")
	}
	llmErr, ok := err.(*LLMError)
	if !ok {
		t.Fatalf("expected *LLMError, got %T: %v", err, err)
	}
	if llmErr.StatusCode != 401 {
		t.Errorf("status code: got %d, want 401", llmErr.StatusCode)
	}
	if llmErr.Retryable {
		t.Error("expected 401 to be non-retryable")
	}
}

func TestAnthropicAdapter_NonStreaming_RateLimitRetryable(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusTooManyRequests)
		fmt.Fprint(w, `{"error":{"type":"rate_limit_error","message":"too many requests"}}`)
	}))
	defer server.Close()

	adapter := NewAnthropicAdapter(AnthropicConfig{APIKey: "k", BaseURL: server.URL})

	_, err := adapter.Call(context.Background(), map[string]interface{}{
		"prompt": "hi",
	}, nil)
	if err == nil {
		t.Fatal("expected error for 429 response")
	}
	llmErr, ok := err.(*LLMError)
	if !ok {
		t.Fatalf("expected *LLMError, got %T", err)
	}
	if !llmErr.Retryable {
		t.Error("expected 429 to be retryable")
	}
}

func TestAnthropicAdapter_NonStreaming_MissingMessages(t *testing.T) {
	adapter := NewAnthropicAdapter(AnthropicConfig{APIKey: "k"})

	_, err := adapter.Call(context.Background(), map[string]interface{}{}, nil)
	if err == nil {
		t.Fatal("expected error for missing messages/prompt")
	}
	if !strings.Contains(err.Error(), "must include 'messages' or 'prompt'") {
		t.Errorf("unexpected error: %v", err)
	}
}

// ---------- streaming tests ----------

func TestAnthropicAdapter_Streaming_Basic(t *testing.T) {
	chunks := []string{"He", "llo", " wo", "rld", "!"}

	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// Verify stream=true in request
		var req anthropicReq
		json.NewDecoder(r.Body).Decode(&req)
		if !req.Stream {
			t.Error("expected stream=true in request body")
		}
		if r.Header.Get("Accept") != "text/event-stream" {
			t.Errorf("expected Accept 'text/event-stream', got %q", r.Header.Get("Accept"))
		}

		w.Header().Set("Content-Type", "text/event-stream")
		w.WriteHeader(http.StatusOK)
		fmt.Fprint(w, anthropicSSEStream("msg_s1", "claude-test", chunks, "end_turn", 12, 8))
	}))
	defer server.Close()

	adapter := NewAnthropicAdapter(AnthropicConfig{
		APIKey:  "test-key",
		Model:   "claude-test",
		BaseURL: server.URL,
	})

	streamCh := make(chan string, 100)
	result, err := adapter.Call(context.Background(), map[string]interface{}{
		"stream": true,
		"messages": []interface{}{
			map[string]interface{}{"role": "user", "content": "say hello world"},
		},
	}, streamCh)
	if err != nil {
		t.Fatalf("Call() error: %v", err)
	}

	// Collect streamed chunks
	close(streamCh)
	var received []string
	for c := range streamCh {
		received = append(received, c)
	}

	if len(received) != len(chunks) {
		t.Errorf("expected %d stream chunks, got %d", len(chunks), len(received))
	}
	for i, want := range chunks {
		if i < len(received) && received[i] != want {
			t.Errorf("chunk[%d]: got %q, want %q", i, received[i], want)
		}
	}

	// Verify assembled result
	if result["content"] != "Hello world!" {
		t.Errorf("content: got %q, want 'Hello world!'", result["content"])
	}
	if result["model"] != "claude-test" {
		t.Errorf("model: got %q, want 'claude-test'", result["model"])
	}
	if result["finish_reason"] != "end_turn" {
		t.Errorf("finish_reason: got %q, want 'end_turn'", result["finish_reason"])
	}
	if result["response_id"] != "msg_s1" {
		t.Errorf("response_id: got %q, want 'msg_s1'", result["response_id"])
	}
	usage := result["usage"].(map[string]interface{})
	if usage["prompt_tokens"] != 12 {
		t.Errorf("prompt_tokens: got %v, want 12", usage["prompt_tokens"])
	}
	if usage["completion_tokens"] != 8 {
		t.Errorf("completion_tokens: got %v, want 8", usage["completion_tokens"])
	}
	if usage["total_tokens"] != 20 {
		t.Errorf("total_tokens: got %v, want 20", usage["total_tokens"])
	}
}

func TestAnthropicAdapter_Streaming_FallsBackWhenNoChannel(t *testing.T) {
	// When stream=true but channel is nil, should fall back to non-streaming
	var captured anthropicReq

	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		json.NewDecoder(r.Body).Decode(&captured)
		w.Header().Set("Content-Type", "application/json")
		fmt.Fprint(w, anthropicJSONResponse("msg_1", "claude-test", "ok", "end_turn", 5, 2))
	}))
	defer server.Close()

	adapter := NewAnthropicAdapter(AnthropicConfig{APIKey: "k", BaseURL: server.URL})

	result, err := adapter.Call(context.Background(), map[string]interface{}{
		"stream": true,
		"prompt": "hi",
	}, nil) // nil channel
	if err != nil {
		t.Fatalf("Call() error: %v", err)
	}
	if captured.Stream {
		t.Error("expected stream=false when channel is nil")
	}
	if result["content"] != "ok" {
		t.Errorf("content: got %v, want 'ok'", result["content"])
	}
}

func TestAnthropicAdapter_Streaming_HTTPError(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusInternalServerError)
		fmt.Fprint(w, `{"error":{"type":"api_error","message":"internal server error"}}`)
	}))
	defer server.Close()

	adapter := NewAnthropicAdapter(AnthropicConfig{APIKey: "k", BaseURL: server.URL})

	streamCh := make(chan string, 100)
	_, err := adapter.Call(context.Background(), map[string]interface{}{
		"stream": true,
		"prompt": "hi",
	}, streamCh)
	if err == nil {
		t.Fatal("expected error for 500 response")
	}
	llmErr, ok := err.(*LLMError)
	if !ok {
		t.Fatalf("expected *LLMError, got %T: %v", err, err)
	}
	if !llmErr.Retryable {
		t.Error("expected 500 to be retryable")
	}
}

func TestAnthropicAdapter_Streaming_ErrorEvent(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "text/event-stream")
		w.WriteHeader(http.StatusOK)
		// Send a partial stream then error
		fmt.Fprint(w, "event: message_start\ndata: {\"type\":\"message_start\",\"message\":{\"id\":\"msg_1\",\"model\":\"claude-test\",\"content\":[],\"usage\":{\"input_tokens\":5}}}\n\n")
		fmt.Fprint(w, "event: error\ndata: {\"type\":\"error\",\"error\":{\"type\":\"overloaded_error\",\"message\":\"Overloaded\"}}\n\n")
	}))
	defer server.Close()

	adapter := NewAnthropicAdapter(AnthropicConfig{APIKey: "k", BaseURL: server.URL})

	streamCh := make(chan string, 100)
	_, err := adapter.Call(context.Background(), map[string]interface{}{
		"stream": true,
		"prompt": "hi",
	}, streamCh)
	if err == nil {
		t.Fatal("expected error from error SSE event")
	}
	if !strings.Contains(err.Error(), "Overloaded") {
		t.Errorf("expected error to mention 'Overloaded', got: %v", err)
	}
}

func TestAnthropicAdapter_Streaming_ContextCancellation(t *testing.T) {
	// Simulate a slow stream and cancel the context
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "text/event-stream")
		w.WriteHeader(http.StatusOK)
		// Write message_start and one chunk
		fmt.Fprint(w, "event: message_start\ndata: {\"type\":\"message_start\",\"message\":{\"id\":\"msg_1\",\"model\":\"claude-test\",\"content\":[],\"usage\":{\"input_tokens\":5}}}\n\n")
		fmt.Fprint(w, "event: content_block_start\ndata: {\"type\":\"content_block_start\",\"index\":0,\"content_block\":{\"type\":\"text\",\"text\":\"\"}}\n\n")
		fmt.Fprint(w, "event: content_block_delta\ndata: {\"type\":\"content_block_delta\",\"index\":0,\"delta\":{\"type\":\"text_delta\",\"text\":\"He\"}}\n\n")
		// Flush to ensure the client receives data
		if f, ok := w.(http.Flusher); ok {
			f.Flush()
		}
		// Block indefinitely (simulating slow stream) — context cancel will close connection
		<-r.Context().Done()
	}))
	defer server.Close()

	adapter := NewAnthropicAdapter(AnthropicConfig{APIKey: "k", BaseURL: server.URL})

	ctx, cancel := context.WithCancel(context.Background())

	// Use a zero-buffer channel so the send blocks when context is cancelled
	streamCh := make(chan string)

	// Read one chunk then cancel
	go func() {
		<-streamCh // read "He"
		cancel()
	}()

	_, err := adapter.Call(ctx, map[string]interface{}{
		"stream": true,
		"prompt": "hi",
	}, streamCh)
	if err == nil {
		t.Fatal("expected context cancellation error")
	}
}

// ---------- structured JSON output tests ----------

func TestAnthropicAdapter_StructuredJSON(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		var req anthropicReq
		json.NewDecoder(r.Body).Decode(&req)
		// Verify schema instruction was injected into system prompt
		if !strings.Contains(req.System, "OUTPUT FORMAT REQUIREMENT") {
			t.Error("expected schema instruction in system prompt")
		}
		if !strings.Contains(req.System, `"name"`) {
			t.Error("expected schema properties in system prompt")
		}

		w.Header().Set("Content-Type", "application/json")
		fmt.Fprint(w, anthropicJSONResponse("msg_1", "claude-test", `{"name":"Alice","age":30}`, "end_turn", 10, 5))
	}))
	defer server.Close()

	adapter := NewAnthropicAdapter(AnthropicConfig{APIKey: "k", BaseURL: server.URL})

	result, err := adapter.Call(context.Background(), map[string]interface{}{
		"prompt": "give me a person",
		"output_config": map[string]interface{}{
			"format": map[string]interface{}{
				"type": "json_schema",
				"schema": map[string]interface{}{
					"type": "object",
					"properties": map[string]interface{}{
						"name": map[string]interface{}{"type": "string"},
						"age":  map[string]interface{}{"type": "number"},
					},
				},
			},
		},
	}, nil)
	if err != nil {
		t.Fatalf("Call() error: %v", err)
	}

	// Content should be parsed JSON, not a string
	parsed, ok := result["content"].(map[string]interface{})
	if !ok {
		t.Fatalf("expected content to be parsed map, got %T: %v", result["content"], result["content"])
	}
	if parsed["name"] != "Alice" {
		t.Errorf("name: got %v, want 'Alice'", parsed["name"])
	}
}

func TestAnthropicAdapter_StructuredJSON_WithCodeFences(t *testing.T) {
	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		// LLM wraps in code fences despite instruction
		fmt.Fprint(w, anthropicJSONResponse("msg_1", "claude-test", "```json\n{\"value\":42}\n```", "end_turn", 10, 5))
	}))
	defer server.Close()

	adapter := NewAnthropicAdapter(AnthropicConfig{APIKey: "k", BaseURL: server.URL})

	result, err := adapter.Call(context.Background(), map[string]interface{}{
		"prompt": "give me a number",
		"output_config": map[string]interface{}{
			"format": map[string]interface{}{"type": "json_schema"},
		},
	}, nil)
	if err != nil {
		t.Fatalf("Call() error: %v", err)
	}

	parsed, ok := result["content"].(map[string]interface{})
	if !ok {
		t.Fatalf("expected parsed map, got %T", result["content"])
	}
	if parsed["value"] != float64(42) {
		t.Errorf("value: got %v, want 42", parsed["value"])
	}
}