using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using SharepointToolbox.Core.Models;
using SharepointToolbox.Services.Export;

namespace SharepointToolbox.Tests.Services.Export;

/// <summary>
/// Unit tests for UserAccessCsvExportService (Phase 7 Plan 08).
/// Verifies: summary section, column count, RFC 4180 escaping, per-user content.
/// </summary>
public class UserAccessCsvExportServiceTests
{
    // ── Helper factory ────────────────────────────────────────────────────────

    private static UserAccessEntry MakeEntry(
        string userDisplay = "Alice Smith",
        string userLogin = "alice@contoso.com",
        string siteUrl = "https://contoso.sharepoint.com",
        string siteTitle = "Contoso",
        string objectType = "List",
        string objectTitle = "Docs",
        string objectUrl = "https://contoso.sharepoint.com/Docs",
        string permLevel = "Read",
        AccessType accessType = AccessType.Direct,
        string grantedThrough = "Direct Permissions",
        bool isHighPrivilege = false,
        bool isExternal = false) =>
        new(userDisplay, userLogin, siteUrl, siteTitle, objectType, objectTitle, objectUrl,
            permLevel, accessType, grantedThrough, isHighPrivilege, isExternal);

    private static readonly UserAccessEntry DefaultEntry = MakeEntry();

    // ── Test 1: BuildCsv includes summary section ─────────────────────────────

    [Fact]
    public void BuildCsv_includes_summary_section()
    {
        var svc = new UserAccessCsvExportService();
        var csv = svc.BuildCsv("Alice Smith", "alice@contoso.com", new[] { DefaultEntry });

        Assert.Contains("User Access Audit Report", csv);
        Assert.Contains("Alice Smith", csv);
        Assert.Contains("alice@contoso.com", csv);
        Assert.Contains("Total Accesses", csv);
        Assert.Contains("Sites", csv);
    }

    // ── Test 2: BuildCsv includes data header line ────────────────────────────

    [Fact]
    public void BuildCsv_includes_data_header()
    {
        var svc = new UserAccessCsvExportService();
        var csv = svc.BuildCsv("Alice Smith", "alice@contoso.com", new[] { DefaultEntry });

        Assert.Contains("Site", csv);
        Assert.Contains("Object Type", csv);
        Assert.Contains("Object", csv);
        Assert.Contains("Permission Level", csv);
        Assert.Contains("Access Type", csv);
        Assert.Contains("Granted Through", csv);
    }

    // ── Test 3: BuildCsv escapes double quotes (RFC 4180) ─────────────────────

    [Fact]
    public void BuildCsv_escapes_quotes()
    {
        var entryWithQuotes = MakeEntry(objectTitle: "Document \"Template\" Library");
        var svc = new UserAccessCsvExportService();
        var csv = svc.BuildCsv("Alice", "alice@contoso.com", new[] { entryWithQuotes });

        // RFC 4180: double quotes inside a quoted field are doubled
        Assert.Contains("\"\"Template\"\"", csv);
    }

    // ── Test 4: BuildCsv data rows have correct column count ──────────────────

    [Fact]
    public void BuildCsv_correct_column_count()
    {
        var svc = new UserAccessCsvExportService();
        var csv = svc.BuildCsv("Alice", "alice@contoso.com", new[] { DefaultEntry });

        // Find the header row and count its quoted comma-separated fields
        // Header is: "Site","Object Type","Object","URL","Permission Level","Access Type","Granted Through"
        // That is 7 fields.
        var lines = csv.Split('\n', StringSplitOptions.RemoveEmptyEntries);

        // Find a data row (after the blank line separating summary from data)
        // Data rows contain the entry content (not the header line itself)
        // We want to count fields in the header row:
        var headerLine = lines.FirstOrDefault(l => l.Contains("\"Site\",\"Object Type\""));
        Assert.NotNull(headerLine);

        // Count comma-separated quoted fields: split by "," boundary
        var fields = CountCsvFields(headerLine!);
        Assert.Equal(7, fields);
    }

    // ── Test 5: WriteSingleFileAsync includes entries for all users ───────────

    [Fact]
    public async Task WriteSingleFileAsync_includes_all_users()
    {
        var alice = MakeEntry(userDisplay: "Alice", userLogin: "alice@contoso.com");
        var bob   = MakeEntry(userDisplay: "Bob",   userLogin: "bob@contoso.com");

        var svc = new UserAccessCsvExportService();
        var tmpFile = Path.GetTempFileName();
        try
        {
            await svc.WriteSingleFileAsync(new[] { alice, bob }, tmpFile, CancellationToken.None);
            var content = await File.ReadAllTextAsync(tmpFile);

            Assert.Contains("alice@contoso.com", content);
            Assert.Contains("bob@contoso.com", content);
            Assert.Contains("Users Audited", content);
        }
        finally
        {
            File.Delete(tmpFile);
        }
    }

    // ── Private helpers ───────────────────────────────────────────────────────

    /// <summary>
    /// Counts the number of comma-separated fields in a CSV line by stripping
    /// surrounding quotes from each field.
    /// </summary>
    private static int CountCsvFields(string line)
    {
        // Simple RFC 4180 field counter — works for well-formed quoted fields
        int count = 1;
        bool inQuotes = false;
        for (int i = 0; i < line.Length; i++)
        {
            char c = line[i];
            if (c == '"')
            {
                if (inQuotes && i + 1 < line.Length && line[i + 1] == '"')
                    i++; // skip escaped quote
                else
                    inQuotes = !inQuotes;
            }
            else if (c == ',' && !inQuotes)
            {
                count++;
            }
        }
        return count;
    }
}