// A path exclusive reservation system
// reserve([list, of, paths], fn)
// When the fn is first in line for all its paths, it
// is called with a cb that clears the reservation.
//
// Used by async unpack to avoid clobbering paths in use,
// while still allowing maximal safe parallelization.
import { join } from 'node:path';
import { normalizeUnicode } from './normalize-unicode.js';
import { stripTrailingSlashes } from './strip-trailing-slashes.js';
const platform = process.env.TESTING_TAR_FAKE_PLATFORM || process.platform;
const isWindows = platform === 'win32';
// return a set of parent dirs for a given path
// '/a/b/c/d' -> ['/', '/a', '/a/b', '/a/b/c', '/a/b/c/d']
const getDirs = (path) => {
    const dirs = path
        .split('/')
        .slice(0, -1)
        .reduce((set, path) => {
        const s = set.at(-1);
        if (s !== undefined) {
            path = join(s, path);
        }
        set.push(path || '/');
        return set;
    }, []);
    return dirs;
};
export class PathReservations {
    // path => [function or Set]
    // A Set object means a directory reservation
    // A fn is a direct reservation on that path
    #queues = new Map();
    // fn => {paths:[path,...], dirs:[path, ...]}
    #reservations = new Map();
    // functions currently running
    #running = new Set();
    reserve(paths, fn) {
        paths =
            isWindows ?
                ['win32 parallelization disabled']
                : paths.map(p => {
                    // don't need normPath, because we skip this entirely for windows
                    return stripTrailingSlashes(join(normalizeUnicode(p)));
                });
        const dirs = new Set(paths.map(path => getDirs(path)).reduce((a, b) => a.concat(b)));
        this.#reservations.set(fn, { dirs, paths });
        for (const p of paths) {
            const q = this.#queues.get(p);
            if (!q) {
                this.#queues.set(p, [fn]);
            }
            else {
                q.push(fn);
            }
        }
        for (const dir of dirs) {
            const q = this.#queues.get(dir);
            if (!q) {
                this.#queues.set(dir, [new Set([fn])]);
            }
            else {
                const l = q.at(-1);
                if (l instanceof Set) {
                    l.add(fn);
                }
                else {
                    q.push(new Set([fn]));
                }
            }
        }
        return this.#run(fn);
    }
    // return the queues for each path the function cares about
    // fn => {paths, dirs}
    #getQueues(fn) {
        const res = this.#reservations.get(fn);
        /* c8 ignore start */
        if (!res) {
            throw new Error('function does not have any path reservations');
        }
        /* c8 ignore stop */
        return {
            paths: res.paths.map((path) => this.#queues.get(path)),
            dirs: [...res.dirs].map(path => this.#queues.get(path)),
        };
    }
    // check if fn is first in line for all its paths, and is
    // included in the first set for all its dir queues
    check(fn) {
        const { paths, dirs } = this.#getQueues(fn);
        return (paths.every(q => q && q[0] === fn) &&
            dirs.every(q => q && q[0] instanceof Set && q[0].has(fn)));
    }
    // run the function if it's first in line and not already running
    #run(fn) {
        if (this.#running.has(fn) || !this.check(fn)) {
            return false;
        }
        this.#running.add(fn);
        fn(() => this.#clear(fn));
        return true;
    }
    #clear(fn) {
        if (!this.#running.has(fn)) {
            return false;
        }
        const res = this.#reservations.get(fn);
        /* c8 ignore start */
        if (!res) {
            throw new Error('invalid reservation');
        }
        /* c8 ignore stop */
        const { paths, dirs } = res;
        const next = new Set();
        for (const path of paths) {
            const q = this.#queues.get(path);
            /* c8 ignore start */
            if (!q || q?.[0] !== fn) {
                continue;
            }
            /* c8 ignore stop */
            const q0 = q[1];
            if (!q0) {
                this.#queues.delete(path);
                continue;
            }
            q.shift();
            if (typeof q0 === 'function') {
                next.add(q0);
            }
            else {
                for (const f of q0) {
                    next.add(f);
                }
            }
        }
        for (const dir of dirs) {
            const q = this.#queues.get(dir);
            const q0 = q?.[0];
            /* c8 ignore next - type safety only */
            if (!q || !(q0 instanceof Set))
                continue;
            if (q0.size === 1 && q.length === 1) {
                this.#queues.delete(dir);
                continue;
            }
            else if (q0.size === 1) {
                q.shift();
                // next one must be a function,
                // or else the Set would've been reused
                const n = q[0];
                if (typeof n === 'function') {
                    next.add(n);
                }
            }
            else {
                q0.delete(fn);
            }
        }
        this.#running.delete(fn);
        next.forEach(fn => this.#run(fn));
        return true;
    }
}
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