#!/usr/bin/env /Library/Frameworks/Mono.framework/Commands/csharp

using System.Diagnostics;
using System.IO;

var args = Environment.GetCommandLineArgs ();
// first arg is "/Library/Frameworks/Mono.framework/Versions/4.8.0/lib/mono/4.5/csharp.exe"
// second arg the script itself
// then comes the ones we care about: the date and the number of weeks

if (args.Length < 5) {
	Console.WriteLine ("Usage: ./xcode-diff.csharp /path/to/base/xcode.app /path/to/new/xcode.app output-subdirectory");
	Environment.Exit (1);
}

// old Xcode did not have a symlink to the latest SDK and could have multiple SDK for simulator
var old_xcode = args [2];
if (!Directory.Exists (old_xcode)) {
	Console.WriteLine ("Cannot find {0}", old_xcode);
	Environment.Exit (1);
}

var new_xcode = args [3];
if (new_xcode.IndexOf (".platform", StringComparison.Ordinal) < 0) {
	Console.WriteLine ("Directory precision mismatch, either provide Xcode paths (for iOS) or specific Frameworks directories for both Xcode targets");
	Environment.Exit (1);
}

var output_dir = args [4];

var unsupportedFrameworks = args.Skip (5).ToHashSet ();

// unique name: {xcode}/{beta}/{platform}/{framework}-{platform}-{xcode}-{beta}.md
var split = output_dir.Split (new char [] { '/' }, StringSplitOptions.RemoveEmptyEntries);
var l = split.Length;
var fileSuffix = $"-{split [l - 1]}-{split [l - 3]}-{split [l - 2]}.md"; 

if (!Directory.Exists (new_xcode)) {
	Console.WriteLine ("Cannot find {0}", new_xcode);
	Environment.Exit (1);
}

var collect = new Func<string,SortedList<string,string>> ((directory) => {
	var list = new SortedList<string,string> ();
	foreach (var fx in Directory.EnumerateDirectories (directory, "*.framework", SearchOption.AllDirectories)) {
		var headers = Path.Combine (fx, "Headers");
		if (!Directory.Exists (headers))
			continue;
		var name = Path.GetFileName (fx);
		var nameOnly = Path.GetFileNameWithoutExtension (name);
		if (unsupportedFrameworks.Contains (nameOnly))
			continue;
		// of course macOS use symlinks to duplicate :(
		if (list.ContainsKey (name))
			continue;
		list.Add (name, headers);
	}
	return list;
});

var differ = new Action<string,string,string> ((fx_name, old_headers, new_headers) => {
	var diff = $"#{fx_name}\n\n";
	diff += "``` diff\n";
	var info = new ProcessStartInfo ("diff", $"-ruN {old_headers} {new_headers}");
	info.RedirectStandardOutput = true;
	info.UseShellExecute = false;
	var p = Process.Start (info);
	var output = p.StandardOutput.ReadToEnd ();
	diff += output;
	p.WaitForExit ();
	if (p.ExitCode == 0 || string.IsNullOrEmpty (output))
		return;
	diff += "\n```";
	var fx_short_name = fx_name.Remove (fx_name.IndexOf ('.'));
	var file = new FileInfo (Path.Combine (output_dir, $"{fx_short_name}{fileSuffix}"));
	file.Directory.Create ();
	File.WriteAllText (file.FullName, diff);
});

var old_fx = collect (old_xcode);
var new_fx = collect (new_xcode);

foreach (var fx in old_fx) {
	if (new_fx.TryGetValue (fx.Key, out var directory)) {
		// diff old and new
		differ (fx.Key, fx.Value, directory);
		new_fx.Remove (fx.Key);
	} else {
		// fx was removed
		var dummy = fx.Value.Replace (old_xcode, new_xcode);
		differ (fx.Key, fx.Value, dummy);
	}
}
// diff remaining new frameworks
foreach (var fx in new_fx) {
	var dummy = fx.Value.Replace (new_xcode, old_xcode);
	differ (fx.Key, dummy, fx.Value);
}

Environment.Exit (0);