using System;
using System.IO;
using System.Linq;
using iText.Kernel.Pdf;
using UtilitatPdf;

internal static class Program
{
    private static string root;
    private static int passed;

    private static void Main()
    {
        root = Path.Combine(Path.GetTempPath(), "utilitatpdf-tests-" + Guid.NewGuid().ToString("N"));
        Directory.CreateDirectory(root);
        try
        {
            Run("single input is copied unchanged", () =>
            {
                string input = Pdf("single.pdf", 101);
                string output = At("single-out.pdf");
                Merge(output, input);
                Equal(File.ReadAllBytes(input), File.ReadAllBytes(output));
            });
            Run("multiple inputs preserve page order", () =>
            {
                string a = Pdf("a.pdf", 101, 102);
                string b = Pdf("b.pdf", 201);
                string c = Pdf("c.pdf", 301, 302);
                byte[] original = File.ReadAllBytes(a);
                Merge(At("merged.pdf"), a, b, c);
                using (var result = new PdfDocument(new PdfReader(At("merged.pdf"))))
                {
                    int[] widths = { 101, 102, 201, 301, 302 };
                    Check(result.GetNumberOfPages() == widths.Length);
                    for (int i = 0; i < widths.Length; i++)
                        Check(result.GetPage(i + 1).GetPageSize().GetWidth() == widths[i]);
                }
                Equal(original, File.ReadAllBytes(a));
            });
            Run("same input and output is rejected", () =>
            {
                string a = Pdf("same.pdf", 100);
                byte[] original = File.ReadAllBytes(a);
                Fails(() => Merge(a, a));
                Equal(original, File.ReadAllBytes(a));
            });
            Run("normalized source path is protected", () =>
            {
                string a = Pdf("normalized.pdf", 100);
                byte[] original = File.ReadAllBytes(a);
                Fails(() => Merge(At("./normalized.pdf"), a, At("b.pdf")));
                Equal(original, File.ReadAllBytes(a));
            });
            Run("existing output survives corrupt later input", () =>
            {
                string output = Pdf("existing.pdf", 999);
                byte[] original = File.ReadAllBytes(output);
                File.WriteAllText(At("broken.pdf"), "not a PDF");
                Fails(() => Merge(output, At("a.pdf"), At("broken.pdf")));
                Equal(original, File.ReadAllBytes(output));
                using (File.Open(At("a.pdf"), FileMode.Open, FileAccess.ReadWrite, FileShare.None)) { }
            });
            Run("failed merge creates no final output", () =>
            {
                string output = At("failed.pdf");
                Fails(() => Merge(output, At("a.pdf"), At("broken.pdf")));
                Check(!File.Exists(output));
            });
            Run("missing source preserves existing output", () =>
            {
                byte[] original = File.ReadAllBytes(At("existing.pdf"));
                Fails(() => Merge(At("existing.pdf"), At("missing.pdf")));
                Equal(original, File.ReadAllBytes(At("existing.pdf")));
            });
            Run("successful merge replaces existing output", () =>
            {
                Merge(At("existing.pdf"), At("a.pdf"), At("b.pdf"));
                using (var result = new PdfDocument(new PdfReader(At("existing.pdf"))))
                    Check(result.GetNumberOfPages() == 3);
            });
            Run("single input replaces existing output", () =>
            {
                Merge(At("existing.pdf"), At("a.pdf"));
                Equal(File.ReadAllBytes(At("a.pdf")), File.ReadAllBytes(At("existing.pdf")));
            });
            Run("overwrite disabled preserves destination", () =>
            {
                byte[] original = File.ReadAllBytes(At("existing.pdf"));
                var merge = new PdfMergeFiles(At("existing.pdf"), false);
                merge.AddFile(At("b.pdf"));
                Fails(merge.Generate);
                Equal(original, File.ReadAllBytes(At("existing.pdf")));
            });
            Run("empty input list preserves destination", () =>
            {
                byte[] original = File.ReadAllBytes(At("existing.pdf"));
                Fails(new PdfMergeFiles(At("existing.pdf")).Generate);
                Equal(original, File.ReadAllBytes(At("existing.pdf")));
            });
            Run("publish failure preserves destination directory", () =>
            {
                string output = At("directory.pdf");
                Directory.CreateDirectory(output);
                File.WriteAllText(Path.Combine(output, "keep.txt"), "keep");
                Fails(() => Merge(output, At("a.pdf")));
                Check(File.ReadAllText(Path.Combine(output, "keep.txt")) == "keep");
            });
            Console.WriteLine($"{passed} regression cases passed.");
        }
        finally { Directory.Delete(root, true); }
    }

    private static string At(string name) => Path.Combine(root, name);
    private static string Pdf(string name, params int[] widths)
    {
        string path = At(name);
        using (var pdf = new PdfDocument(new PdfWriter(path)))
            foreach (int width in widths)
                pdf.AddNewPage(new iText.Kernel.Geom.PageSize(width, 400));
        return path;
    }
    private static void Merge(string output, params string[] inputs)
    {
        var merger = new PdfMergeFiles(output);
        foreach (string input in inputs) merger.AddFile(input);
        merger.Generate();
    }
    private static void Check(bool condition)
    {
        if (!condition) throw new Exception("Assertion failed.");
    }
    private static void Equal(byte[] expected, byte[] actual) => Check(expected.SequenceEqual(actual));
    private static void Fails(Action action)
    {
        try { action(); }
        catch (Exception) { return; }
        throw new Exception("Expected the operation to fail.");
    }
    private static void Run(string name, Action action)
    {
        action();
        Check(Directory.GetFiles(root, ".utilitatpdf-*.tmp").Length == 0);
        Console.WriteLine("PASS " + name);
        passed++;
    }
}