import { monitorFile, readFile } from "ags/file";
import { timeout } from "ags/time";
import { exec, execAsync } from "ags/process";

import AstalIO from "gi://AstalIO";
import App from "ags/gtk4/app";
import Gio from "gi://Gio?version=2.0";
import GLib from "gi://GLib?version=2.0";


/** handles stylesheet compiling and reloading */
export class Stylesheet {
    private static instance: Stylesheet;
    #watchDelay: (AstalIO.Time|undefined);
    #outputPath = Gio.File.new_for_path(`${GLib.get_user_cache_dir()}/colorshell/style`);
    #styles = [ "./style", "./style.scss" ];

    public get stylePath() { return this.#outputPath.get_path()!; }

    public async compileSass(): Promise<void> {
        console.log("Stylesheet: Compiling Sass");

        exec(`bash -c "sass ${this.#styles.map(style => `-I ${style}`).join('\s')} ${
            this.#outputPath.get_path()!}/style.css"`);
    }

    public async reapply(cssFilePath: string): Promise<void> {
        console.log("Stylesheet: Applying stylesheet");

        const content = readFile(cssFilePath);

        if(content?.trim()) {
            App.reset_css();
            App.apply_css(content);

            console.log("Stylesheet: done applying stylesheet to shell");
            return;
        }

        console.error(`Stylesheet: An error occurred while trying to read the css file: ${
            cssFilePath}`);
    }

    public async compileApply(): Promise<void> {
        await this.compileSass().then(() => 
            this.reapply(this.#outputPath.get_path()! + "/style.css")
        ).catch((err: Error) => 
            console.error(`Stylesheet: An error occurred and Sass couldn't be compiled. Stderr:\n${
                err.message}\n${err.stack}`)
        );
    }

    public static getDefault(): Stylesheet {
        if(!this.instance)
            this.instance = new Stylesheet();

        return this.instance;
    }

    constructor() {
        (async () => !this.#outputPath.query_exists(null) && 
            this.#outputPath.make_directory_with_parents(null))();

        this.#styles.map((path: string) =>
            monitorFile(
                `${path}`,
                (file: string) => {
                    if(this.#watchDelay || file.endsWith('~') || Number.isNaN(file)) 
                        return;

                    this.#watchDelay = timeout(250, () => this.#watchDelay = undefined);
                    console.log(`Stylesheet: \`${file.startsWith(GLib.get_home_dir()) ? 
                            file.replace(GLib.get_home_dir(), '~')
                        : file}\` changed`)

                    this.compileApply();
                }
            )
        )

        monitorFile(`${GLib.get_user_cache_dir()}/wal/colors.scss`, (file: string) => {
            execAsync(`bash -c "cp -f ${file} ./style/_wal.scss"`).catch(r => {
                console.error(`Stylesheet: Failed to copy pywal stylesheet to style dir. Stderr: ${r}`);
            });
        });
    }
}