// AUTOGENERATED COPYRIGHT HEADER START
// Copyright (C) 2023 Michael Fabian 'Xaymar' Dirks <info@xaymar.com>
// AUTOGENERATED COPYRIGHT HEADER END
const CHILD_PROCESS = require("node:child_process");
const PROCESS = require("node:process");
const PATH = require("node:path");
const FS = require("node:fs");
const FSPROMISES = require("node:fs/promises");
const OS = require("os");

const SECTION_START = "AUTOGENERATED COPYRIGHT HEADER START";
const SECTION_END = "AUTOGENERATED COPYRIGHT HEADER END";
const IGNORED = [
	/^\.git$/gi,
	/^cmake\/clang$/gi,
	/^cmake\/version$/gi,
	/^third-party$/gi,
]

let abortAllWork = false;
class RateLimiter {
	constructor(limit = undefined) {
		const OS = require("node:os");
		this._limit = limit;
		if (!this._limit) {
			this._limit = Math.ceil(Math.max(2, OS.cpus().length / 3 * 2));
		}
		this._cur = this._limit;
		this._pend = 0;
		this._locks = [];
	}

	async run(runner) {
		// Use Promises to spin-lock this execution path until there is a free slot.
		this._pend += 1;
		while (true) {
			if (this._cur > 0) {
				this._cur -= 1;
				break;
			} else {
				await Promise.race(this._locks);
			}
		}
		this._pend -= 1;

		let data = {};
		data.pri = new Promise((resolve, reject) => {
			try {
				if (runner.constructor.name == "AsyncFunction") {
					runner().then((res) => {
						resolve(res);
					}, (err) => {
						reject(err);
					})
				} else {
					resolve(runner());
				}
			} catch (ex) {
				reject(ex);
			}
		});
		data.sec = data.pri.finally(() => {
			// Remove this promise from the locks list.
			let idx = this._locks.indexOf(data.pri);
			if (idx >= 0) {
				this._locks.splice(idx, 1);
			}
			let idx2 = this._locks.indexOf(data.sec);
			if (idx2 >= 0) {
				this._locks.splice(idx2, 1);
			}
			this._cur += 1;
			//console.log(`Avail: ${this._cur} / ${this._limit}; Pending: ${this._pend}`)
		});
		this._locks.push(data.sec);
		return await data.sec;
	}
}

let gitRL = new RateLimiter(1);
let workRL = new RateLimiter();

async function isIgnored(path) {
	let rpath = PATH.relative(process.cwd(), path).replaceAll(PATH.sep, PATH.posix.sep);
	for (let ignore of IGNORED) {
		if (ignore instanceof RegExp) {
			if (ignore.global) {
				let matches = rpath.matchAll(ignore);
				for (let match of matches) {
					return true;
				}
			} else {
				if (rpath.match(ignore) !== null) {
					return true;
				}
			}
		} else if (rpath.startsWith(ignore)) {
			return true;
		}
	}

	return await gitRL.run(async () => {
		return await new Promise((resolve, reject) => {
			try {
				let proc = CHILD_PROCESS.spawn("git", [
					"check-ignore",
					path
				], {
					"cwd": PROCESS.cwd(),
					"encoding": "utf8",
				});
				proc.stdout.on('data', (data) => {
				})
				proc.on('close', (code) => {
					resolve(code == 0);
				});
				proc.on('exit', (code) => {
					resolve(code == 0);
				});
			} catch (ex) {
				reject(ex);
			}
		});
	});
}

async function git_retrieveAuthors(file) {
	// git --no-pager log --date-order --reverse "--format=format:%aI|%aN <%aE>" -- file
	let lines = await gitRL.run(async () => {
		return await new Promise((resolve, reject) => {
			try {
				let chunks = [];
				let proc = CHILD_PROCESS.spawn("git", [
					"--no-pager",
					"log",
					"--follow",
					"--format=format:%aI|%aN <%aE>",
					"--",
					file
				], {
					"cwd": PROCESS.cwd(),
					"encoding": "utf8",
				});
				proc.stdout.on('data', (chunk) => {
					chunks.push(chunk);
				});
				proc.stdout.on('close', () => {
					let chunk = proc.stdout.read();
					if (chunk) {
						chunks.push(chunk);
					}
				});
				proc.on('exit', (code) => {
					// Merge all data into one buffer.
					let length = 0;
					for (let chunk of chunks) {
						length += chunk.byteLength;
					}
					let buf = Buffer.alloc(length);
					length = 0;
					for (let chunk of chunks) {
						if (!(chunk instanceof Buffer)) {
							chunk = Buffer.from(chunk);
						}
						chunk.copy(buf, length, 0);
						length += chunk.byteLength;
					}

					if (code == 0) {
						if (buf) {
							resolve(buf.toString());
						} else {
							reject(code);
						}
					} else {
						reject(code);
					}
				});
			} catch (ex) {
				reject(ex);
			}
		});
	});

	lines = lines.split(lines.indexOf("\r\n") >= 0 ? "\r\n" : "\n");
	let authors = new Map();
	for (let line of lines) {
		let [date, name] = line.split("|");

		let author = authors.get(name);
		if (author) {
			let dt = new Date(date)
			if (author.from > dt)
				author.from = dt;
			if (author.to < dt)
				author.to = dt;
		} else {
			authors.set(name, {
				from: new Date(date),
				to: new Date(date),
			})
		}
	}
	return authors;
}

async function generateCopyright(file) {
	let authors = await git_retrieveAuthors(file)
	authors = new Map([...authors].sort((a, b) => {
		if (a[1].from < b[1].from) {
			return -1;
		} else if (a[1].from > b[1].from) {
			return 1;
		}
		return 0;
	}));
	let lines = [];
	for (let entry of authors) {
		let from = entry[1].from.getUTCFullYear();
		let to = entry[1].to.getUTCFullYear();
		lines.push(`Copyright (C) ${from != to ? `${from}-${to}` : to} ${entry[0]}`);
	}
	return lines;
}

function makeHeader(file, copyright) {
	let file_name = PATH.basename(file).toLocaleLowerCase();
	let file_exts = file_name.substring(file_name.indexOf("."));

	let styles = {
		"#": {
			files: [
				"cmakelists.txt"
			], exts: [
				".clang-tidy",
				".clang-format",
				".cmake",
				".editorconfig",
				".gitignore",
				".gitmodules",
				".yml",
			],
			prepend: [
				`# ${SECTION_START}`,
			],
			append: [
				`# ${SECTION_END}`,
			],
			prefix: "# ",
			suffix: "",
		},
		";": {
			files: [
				""
			], exts: [
				".iss",
				".iss.in",
			],
			prepend: [
				`; ${SECTION_START}`,
			],
			append: [
				`; ${SECTION_END}`,
			],
			prefix: "; ",
			suffix: "",
		},
		"//": {
			files: [
			], exts: [
				".c",
				".c.in",
				".cpp",
				".cpp.in",
				".h",
				".h.in",
				".hpp",
				".hpp.in",
				".js",
				".rc",
				".rc.in",
				".effect"
			],
			prepend: [
				`// ${SECTION_START}`,
			],
			append: [
				`// ${SECTION_END}`,
			],
			prefix: "// ",
			suffix: "",
		},
		"<!---->": {
			files: [
			], exts: [
				".htm",
				".htm.in",
				".html",
				".html.in",
				".xml",
				".xml.in",
				".plist",
				".plist.in",
				".pkgproj",
				".pkgproj.in",
			],
			prepend: [
				`<!-- ${SECTION_START} -->`,
			],
			append: [
				`<!-- ${SECTION_END} -->`,
			],
			prefix: "<!-- ",
			suffix: " -->",
		}
	};

	for (let key in styles) {
		let style = [key, styles[key]];
		if (style[1].files.includes(file_name)
			|| style[1].files.includes(file)
			|| style[1].exts.includes(file_exts)) {
			let header = [];
			header.push(...style[1].prepend);
			for (let line of copyright) {
				header.push(`${style[1].prefix}${line}${style[1].suffix}`);
			}
			header.push(...style[1].append);
			return header;
		}
	}

	throw new Error("Unrecognized file format.")
}

async function updateFile(file) {
	await workRL.run(async () => {
		try {
			if (abortAllWork) {
				return;
			}

			// Copyright information.
			let copyright = await generateCopyright(file);
			let header = undefined;
			try {
				header = makeHeader(file, copyright);
			} catch (ex) {
				console.log(`Skipping file '${file}'...`);
				return;
			}
			console.log(`Updating file '${file}'...`);

			// File contents.
			let content = await FSPROMISES.readFile(file);
			let eol = (content.indexOf("\r\n") != -1 ? OS.EOL : "\n");
			let insert = Buffer.from(header.join(eol) + eol);

			// Find the starting point.
			let startHeader = content.indexOf(SECTION_START);
			startHeader = content.lastIndexOf(eol, startHeader);
			startHeader += Buffer.from(eol).byteLength;

			// Find the ending point.
			let endHeader = content.indexOf(SECTION_END);
			endHeader = content.indexOf(eol, endHeader);
			endHeader += Buffer.from(eol).byteLength;

			if (abortAllWork) {
				return;
			}

			let fd = await FSPROMISES.open(file, "w");
			let fp = [];
			if ((startHeader >= 0) && (endHeader > startHeader)) {
				let pos = 0;
				if (startHeader > 0) {
					fd.write(content, 0, startHeader, 0);
					pos += startHeader;
				}
				fd.write(insert, 0, undefined, pos);
				pos += insert.byteLength;
				fd.write(content, endHeader, undefined, pos);
			} else {
				fd.write(insert, 0, undefined, 0);
				fd.write(content, 0, undefined, insert.byteLength);
			}
			await fd.close();
		} catch (ex) {
			console.error(`Error processing '${file}'!: ${ex}`);
			abortAllWork = true;
			PROCESS.exitCode = 1;
			return;
		}
	});
}

async function scanPath(path) {
	// Abort here if the user aborted the process, or if the path is ignored.
	if (abortAllWork) {
		return;
	}

	let promises = [];

	await workRL.run(async () => {
		let files = await FSPROMISES.readdir(path, { "withFileTypes": true });
		for (let file of files) {
			if (abortAllWork) {
				break;
			}

			let fullname = PATH.join(path, file.name);
			if (await isIgnored(fullname)) {
				console.log(`Ignoring path '${fullname}'...`);
				continue;
			}

			if (file.isDirectory()) {
				console.log(`Scanning path '${fullname}'...`);
				promises.push(scanPath(fullname));
			} else {
				promises.push(updateFile(fullname));
			}
		}
	});

	await Promise.all(promises);
}

(async function () {
	PROCESS.on("SIGINT", () => {
		abortAllWork = true;
		PROCESS.exitCode = 1;
		console.log("Sanely aborting all pending work...");
	})

	let path = PATH.resolve(PROCESS.argv[2]);

	{ // Bootstrap to actually be in the directory where '.git' is.
		let is_git_directory = false;
		while (!is_git_directory) {
			if (abortAllWork) {
				return;
			}

			let entries = await FSPROMISES.readdir(PROCESS.cwd());
			if (entries.includes(".git")) {
				console.log(`Found .git at '${process.cwd()}'.`);
				is_git_directory = true;
			} else {
				PROCESS.chdir(PATH.resolve(PATH.join(PROCESS.cwd(), "..")));
			}
		}
		path = PATH.normalize(PATH.relative(process.cwd(), path));
	}

	if (!await isIgnored(path)) {
		if ((await FSPROMISES.stat(path)).isDirectory()) {
			console.log(`Scanning path '${path}'...`);
			await scanPath(path);
		} else {
			await updateFile(path);
		}
	} else {
		console.log(`Ignoring path '${path}'...`);
	}
	console.log("Done");
})();