package llm

import (
	"context"
	"encoding/json"
	"errors"
	"net/http"
	"net/http/httptest"
	"strings"
	"testing"
	"time"

	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
)

func TestOpenAICompatibleClientGenerateSuccess(t *testing.T) {
	type observedRequest struct {
		Authorization string
		Body          map[string]any
	}
	obs := &observedRequest{}

	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		obs.Authorization = r.Header.Get("Authorization")
		if r.URL.Path != "/v1/chat/completions" {
			t.Fatalf("unexpected path: %s", r.URL.Path)
		}
		if ct := r.Header.Get("Content-Type"); ct != "application/json" {
			t.Fatalf("unexpected content type: %s", ct)
		}

		defer r.Body.Close()
		if err := json.NewDecoder(r.Body).Decode(&obs.Body); err != nil {
			t.Fatalf("failed to decode request body: %v", err)
		}

		w.Header().Set("Content-Type", "application/json")
		_, _ = w.Write([]byte(`{
  "choices": [{"message": {"role": "assistant", "content": "hello from model"}}],
  "usage": {"prompt_tokens": 11, "completion_tokens": 22, "total_tokens": 33}
}`))
	}))
	defer ts.Close()

	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
		BaseURL: ts.URL + "/v1",
		APIKey:  "secret-key",
		Timeout: 2 * time.Second,
	})
	if err != nil {
		t.Fatalf("unexpected constructor error: %v", err)
	}

	resp, err := client.Generate(context.Background(), domain.GenerateRequest{
		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{
			{Role: "system", Content: "You are helpful."},
			{Role: "user", Content: "Say hello"},
		}},
		Target: domain.ModelTarget{
			Model:       "gpt-test",
			Temperature: 0.4,
			MaxTokens:   123,
			TopP:        0.7,
		},
	})
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}

	if resp.Content != "hello from model" {
		t.Fatalf("unexpected content: %q", resp.Content)
	}
	if resp.Usage.PromptTokens != 11 || resp.Usage.CompletionTokens != 22 || resp.Usage.TotalTokens != 33 {
		t.Fatalf("unexpected usage: %+v", resp.Usage)
	}

	if obs.Authorization != "Bearer secret-key" {
		t.Fatalf("unexpected Authorization header: %q", obs.Authorization)
	}
	if got, ok := obs.Body["model"].(string); !ok || got != "gpt-test" {
		t.Fatalf("unexpected model payload: %#v", obs.Body["model"])
	}

	msgs, ok := obs.Body["messages"].([]any)
	if !ok || len(msgs) != 2 {
		t.Fatalf("unexpected messages payload: %#v", obs.Body["messages"])
	}
	msg0 := msgs[0].(map[string]any)
	if msg0["role"] != "system" || msg0["content"] != "You are helpful." {
		t.Fatalf("unexpected first message: %#v", msg0)
	}
	msg1 := msgs[1].(map[string]any)
	if msg1["role"] != "user" || msg1["content"] != "Say hello" {
		t.Fatalf("unexpected second message: %#v", msg1)
	}
}

func TestOpenAICompatibleClientNoAuthorizationHeaderWhenNoAPIKey(t *testing.T) {
	hadAuth := false
	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		hadAuth = r.Header.Get("Authorization") != ""
		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"ok"}}]}`))
	}))
	defer ts.Close()

	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: ts.URL + "/v1"})
	if err != nil {
		t.Fatal(err)
	}

	_, err = client.Generate(context.Background(), domain.GenerateRequest{
		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
		Target: domain.ModelTarget{Model: "model"},
	})
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}
	if hadAuth {
		t.Fatal("did not expect Authorization header")
	}
}

func TestOpenAICompatibleClientModelFallbackFromConfig(t *testing.T) {
	gotModel := ""
	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		var body map[string]any
		_ = json.NewDecoder(r.Body).Decode(&body)
		if m, ok := body["model"].(string); ok {
			gotModel = m
		}
		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"ok"}}]}`))
	}))
	defer ts.Close()

	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: ts.URL + "/v1", Model: "default-model"})
	if err != nil {
		t.Fatal(err)
	}

	_, err = client.Generate(context.Background(), domain.GenerateRequest{
		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
		Target: domain.ModelTarget{},
	})
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}
	if gotModel != "default-model" {
		t.Fatalf("expected default model, got %q", gotModel)
	}
}

func TestOpenAICompatibleClientEndpointOverride(t *testing.T) {
	defaultHit := false
	overrideHit := false

	defaultServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		defaultHit = true
		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"default"}}]}`))
	}))
	defer defaultServer.Close()

	overrideServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		overrideHit = true
		if r.URL.Path != "/v1/chat/completions" {
			t.Fatalf("unexpected path: %s", r.URL.Path)
		}
		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"override"}}]}`))
	}))
	defer overrideServer.Close()

	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: defaultServer.URL + "/v1", Model: "m"})
	if err != nil {
		t.Fatal(err)
	}

	resp, err := client.Generate(context.Background(), domain.GenerateRequest{
		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
		Target: domain.ModelTarget{Endpoint: overrideServer.URL + "/v1"},
	})
	if err != nil {
		t.Fatalf("expected no error, got %v", err)
	}
	if resp.Content != "override" {
		t.Fatalf("expected override response, got %q", resp.Content)
	}
	if defaultHit {
		t.Fatal("default endpoint should not have been called")
	}
	if !overrideHit {
		t.Fatal("override endpoint should have been called")
	}
}

func TestOpenAICompatibleClientNon2xxError(t *testing.T) {
	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusBadRequest)
		_, _ = w.Write([]byte(`{"error":"bad request payload"}`))
	}))
	defer ts.Close()

	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: ts.URL + "/v1", Model: "m"})
	if err != nil {
		t.Fatal(err)
	}

	_, err = client.Generate(context.Background(), domain.GenerateRequest{
		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
	})
	if err == nil {
		t.Fatal("expected non-2xx error")
	}
	if !errors.Is(err, ErrUnexpectedStatus) {
		t.Fatalf("expected ErrUnexpectedStatus, got %v", err)
	}
	if !strings.Contains(err.Error(), "400") || !strings.Contains(err.Error(), "bad request payload") {
		t.Fatalf("expected status/body details, got %v", err)
	}
}

func TestOpenAICompatibleClientMalformedResponseInvalidJSON(t *testing.T) {
	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		_, _ = w.Write([]byte(`{not valid json`))
	}))
	defer ts.Close()

	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: ts.URL + "/v1", Model: "m"})
	if err != nil {
		t.Fatal(err)
	}

	_, err = client.Generate(context.Background(), domain.GenerateRequest{
		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
	})
	if err == nil {
		t.Fatal("expected malformed response error")
	}
	if !errors.Is(err, ErrMalformedResponse) {
		t.Fatalf("expected ErrMalformedResponse, got %v", err)
	}
}

func TestOpenAICompatibleClientMalformedResponseMissingChoices(t *testing.T) {
	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		_, _ = w.Write([]byte(`{"choices": []}`))
	}))
	defer ts.Close()

	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: ts.URL + "/v1", Model: "m"})
	if err != nil {
		t.Fatal(err)
	}

	_, err = client.Generate(context.Background(), domain.GenerateRequest{
		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
	})
	if err == nil {
		t.Fatal("expected malformed response error")
	}
	if !errors.Is(err, ErrMalformedResponse) {
		t.Fatalf("expected ErrMalformedResponse, got %v", err)
	}
}

func TestOpenAICompatibleClientTimeout(t *testing.T) {
	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		time.Sleep(250 * time.Millisecond)
		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"ok"}}]}`))
	}))
	defer ts.Close()

	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
		BaseURL: ts.URL + "/v1",
		Model:   "m",
		Timeout: 50 * time.Millisecond,
	})
	if err != nil {
		t.Fatal(err)
	}

	_, err = client.Generate(context.Background(), domain.GenerateRequest{
		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
	})
	if err == nil {
		t.Fatal("expected timeout error")
	}
	if !errors.Is(err, ErrRequestFailed) {
		t.Fatalf("expected ErrRequestFailed, got %v", err)
	}
}