package llm

import (
	"context"
	"errors"
	"io"
	"net/http"
	"strings"
	"testing"
)

func TestOpenAICompatibleClientStructuredNonSuccessResponse(t *testing.T) {
	body := `{"error":{"message":"  provider\nmessage\u200b","type":"invalid\ttype","code":1.5e+4}}`
	responseBody := &countingReadCloser{reader: strings.NewReader(body)}
	client := newNonSuccessResponseClient(t, http.StatusBadRequest, int64(len(body)), responseBody)

	response, err := client.Generate(context.Background(), ordinaryGenerateRequest())
	if response != nil {
		t.Fatalf("response = %#v, want nil", response)
	}
	if !errors.Is(err, ErrUnexpectedStatus) {
		t.Fatalf("errors.Is(%v, ErrUnexpectedStatus) = false", err)
	}
	var providerHTTPError *ProviderHTTPError
	if !errors.As(err, &providerHTTPError) {
		t.Fatalf("error = %T, want *ProviderHTTPError", err)
	}
	if providerHTTPError.StatusCode() != http.StatusBadRequest || providerHTTPError.ProviderCode() != "1.5e+4" || providerHTTPError.ProviderType() != "invalid type" || providerHTTPError.ProviderMessage() != "provider message" {
		t.Fatalf("provider error = %#v", providerHTTPError)
	}
	if !responseBody.closed {
		t.Fatal("non-success response body was not closed")
	}
}

func TestOpenAICompatibleClientNonSuccessBodyOwnership(t *testing.T) {
	const marker = "provider-body-marker"
	normalBody := `{"error":{"message":"` + marker + `"}}`
	overLimitBody := normalBody + strings.Repeat(" ", int(maxProviderErrorResponseBytes)+1-len(normalBody))
	tests := []struct {
		name          string
		contentLength int64
		reader        io.Reader
		wantRead      int64
		wantMessage   string
	}{
		{
			name:          "normal",
			contentLength: int64(len(normalBody)),
			reader:        strings.NewReader(normalBody),
			wantRead:      int64(len(normalBody)),
			wantMessage:   marker,
		},
		{
			name:          "declared oversize",
			contentLength: maxProviderErrorResponseBytes + 1,
			reader:        strings.NewReader(normalBody),
			wantRead:      0,
		},
		{
			name:          "streamed oversize",
			contentLength: -1,
			reader: &guardedReader{
				reader:    strings.NewReader(overLimitBody),
				remaining: maxProviderErrorResponseBytes + 1,
			},
			wantRead: maxProviderErrorResponseBytes + 1,
		},
		{
			name:          "underreported oversize",
			contentLength: maxProviderErrorResponseBytes,
			reader: &guardedReader{
				reader:    strings.NewReader(overLimitBody),
				remaining: maxProviderErrorResponseBytes + 1,
			},
			wantRead: maxProviderErrorResponseBytes + 1,
		},
		{
			name:          "malformed",
			contentLength: 1,
			reader:        strings.NewReader("{"),
			wantRead:      1,
		},
		{
			name:          "read failure",
			contentLength: -1,
			reader:        failingReader{err: errors.New("response read failed")},
			wantRead:      0,
		},
	}

	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			body := &countingReadCloser{reader: tc.reader}
			client := newNonSuccessResponseClient(t, http.StatusBadGateway, tc.contentLength, body)

			response, err := client.Generate(context.Background(), ordinaryGenerateRequest())
			if response != nil {
				t.Fatalf("response = %#v, want nil", response)
			}
			var providerHTTPError *ProviderHTTPError
			if !errors.As(err, &providerHTTPError) {
				t.Fatalf("error = %T, want *ProviderHTTPError", err)
			}
			if !body.closed {
				t.Fatal("response body was not closed")
			}
			if body.bytesRead != tc.wantRead {
				t.Fatalf("body bytes read = %d, want %d", body.bytesRead, tc.wantRead)
			}
			if body.bytesRead > maxProviderErrorResponseBytes+1 {
				t.Fatalf("body bytes read = %d, exceeds overflow probe", body.bytesRead)
			}
			if guarded, ok := tc.reader.(*guardedReader); ok && guarded.violated {
				t.Fatal("body reader was asked to read beyond the overflow probe")
			}
			if got := providerHTTPError.ProviderMessage(); got != tc.wantMessage {
				t.Fatalf("provider message = %q, want %q", got, tc.wantMessage)
			}
			if tc.wantMessage == "" && (providerHTTPError.ProviderCode() != "" || providerHTTPError.ProviderType() != "" || strings.Contains(providerHTTPError.Error(), marker)) {
				t.Fatalf("discarded details were retained: %#v", providerHTTPError)
			}
		})
	}
}

func newNonSuccessResponseClient(t *testing.T, statusCode int, contentLength int64, body io.ReadCloser) *OpenAICompatibleClient {
	t.Helper()

	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
		BaseURL: "https://provider.example/v1",
		Model:   "m",
		HTTPClient: &http.Client{Transport: roundTripFunc(func(*http.Request) (*http.Response, error) {
			return &http.Response{
				StatusCode:    statusCode,
				ContentLength: contentLength,
				Body:          body,
			}, nil
		})},
	})
	if err != nil {
		t.Fatalf("construct client: %v", err)
	}
	return client
}