package arxiva

import (
	"bytes"
	"encoding/json"
	"errors"
	"io"
	"net/http"
	"os"
	"testing"
)

// Mock HTTP client that implements the http.RoundTripper interface
type mockTransport struct {
	response *http.Response
	err      error
}

func (m *mockTransport) RoundTrip(req *http.Request) (*http.Response, error) {
	return m.response, m.err
}

func TestFetchPapers(t *testing.T) {
	tests := []struct {
		name         string
		mockResponse string
		mockError    error
		expectError  bool
	}{
		{
			name: "successful fetch",
			mockResponse: `<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">
  <entry>
    <title>Test Paper</title>
    <summary>Test summary</summary>
    <id>http://arxiv.org/abs/1234.56789</id>
  </entry>
</feed>`,
			expectError: false,
		},
		{
			name:        "api error",
			mockError:   errors.New("API unavailable"),
			expectError: true,
		},
		{
			name:         "invalid json",
			mockResponse: "invalid json",
			expectError:  true,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			// Setup mock HTTP client
			var client *http.Client
			var response *http.Response
			if tt.mockError == nil {
				response = &http.Response{
					StatusCode: http.StatusOK,
					Body:       io.NopCloser(bytes.NewBufferString(tt.mockResponse)),
				}
			}
			client = &http.Client{
				Transport: &mockTransport{
					response: response,
					err:      tt.mockError,
				},
			}

			// Replace default client with mock
			originalClient := httpClient
			httpClient = client
			defer func() { httpClient = originalClient }()

			// Test function
			papers, err := FetchPapers("20240101", "20240125", "test", 1)
			if err != nil {
				t.Logf("FetchPapers error: %v", err)
			}
			if (err != nil) != tt.expectError {
				t.Errorf("FetchPapers() error = %v, expectError %v", err, tt.expectError)
				return
			}

			if !tt.expectError && len(papers) == 0 {
				t.Error("Expected papers but got none")
			}
		})
	}
}

func TestSaveToFile(t *testing.T) {
	tests := []struct {
		name        string
		papers      []Paper
		expectError bool
	}{
		{
			name: "successful save",
			papers: []Paper{
				{
					Title:    "Test Paper",
					Abstract: "Test abstract",
					ArxivID:  "1234.56789",
				},
			},
			expectError: false,
		},
		{
			name:        "empty papers",
			papers:      []Paper{},
			expectError: true,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			// Create temp file
			tmpFile, err := os.CreateTemp("", "test-*.json")
			if err != nil {
				t.Fatal(err)
			}
			defer os.Remove(tmpFile.Name())

			// Test function
			filename := "20240101-20240125-test.json"
			err = SaveToFile(tt.papers, "20240101", "20240125", "test")
			if err != nil && !tt.expectError {
				t.Errorf("SaveToFile() unexpected error: %v", err)
				return
			}
			if err == nil && tt.expectError {
				t.Errorf("SaveToFile() expected error but got none")
				return
			}
			if tt.expectError {
				return
			}

			// Clean up test file
			defer os.Remove(filename)
			if (err != nil) != tt.expectError {
				t.Errorf("SaveToFile() error = %v, expectError %v", err, tt.expectError)
				return
			}

			// Verify file contents if successful
			if !tt.expectError {
				var savedPapers []Paper
				fileData, err := os.ReadFile(filename)
				if err != nil {
					t.Errorf("Failed to read saved file: %v", err)
					return
				}

				if err := json.Unmarshal(fileData, &savedPapers); err != nil {
					t.Errorf("Failed to unmarshal saved file: %v", err)
					return
				}

				if len(savedPapers) != len(tt.papers) {
					t.Errorf("Expected %d papers, got %d", len(tt.papers), len(savedPapers))
				}
			} else if tt.name == "empty papers" {
				if _, err := os.Stat(filename); !os.IsNotExist(err) {
					t.Errorf("File should not exist for empty papers case")
				}
			}
		})
	}
}