@puppeteer/browsers/lib/ProgressBar.js

Download and launch browsers

/**
 * @license
 * Copyright 2026 Google Inc.
 * SPDX-License-Identifier: Apache-2.0
 */
// Module-level active session. Concurrent bars share a session; a new session
// starts whenever no bar is currently active (or the stream changes).
let activeBar = null;
/**
 * Manages one or more concurrent progress bars on separate terminal lines.
 * Use {@link ProgressBar.createBarTicker} to add a bar; concurrent calls
 * automatically share a session so bars don't overwrite each other.
 *
 * @internal
 */
export class ProgressBar {
    #stream;
    #totalRows = 0;
    #doneCount = 0;
    #bars = [];
    #renderScheduled = false;
    #lastRenderTime = 0;
    #allDone = false;
    constructor(stream) {
        this.#stream = stream;
    }
    /**
     * Returns a `tick(delta)` function for a new progress bar. If another bar
     * is already active on the same stream, the new bar appears on the next line
     * and both update in place. The trailing newline is emitted automatically
     * once every bar in the session has reached 100%.
     */
    static createBarTicker(title, total, stream = process.stderr) {
        // Start a fresh session when none is active or the stream changed.
        if (!activeBar || activeBar.#stream !== stream) {
            activeBar = new ProgressBar(stream);
        }
        return activeBar.#addBar(title, total);
    }
    #claimRow() {
        const row = this.#totalRows++;
        if (row > 0 && this.#stream.isTTY) {
            // Cursor is parked at col 0 of the previous bottom row; \n opens the
            // new line and moves the cursor there, establishing the new bottom row.
            this.#stream.write('\n');
        }
        return row;
    }
    #addBar(title, total) {
        const row = this.#claimRow();
        this.#bars.push({
            title,
            total,
            downloaded: 0,
            startTime: 0,
            lastRendered: '',
        });
        let doneNotified = false;
        return (delta) => {
            const bar = this.#bars[row];
            if (bar.startTime === 0) {
                bar.startTime = Date.now();
            }
            bar.downloaded += delta;
            const isDone = bar.downloaded >= bar.total;
            if (isDone || Date.now() - this.#lastRenderTime >= 100) {
                this.#scheduleRender();
            }
            if (isDone && !doneNotified) {
                doneNotified = true;
                this.#onBarDone();
            }
        };
    }
    // Defers to a microtask so multiple ticks in the same turn share one render
    // pass and the cursor only moves once.
    #scheduleRender() {
        if (!this.#renderScheduled) {
            this.#renderScheduled = true;
            queueMicrotask(() => {
                this.#renderScheduled = false;
                this.#lastRenderTime = Date.now();
                this.#renderAll();
            });
        }
    }
    #computeRendered(row) {
        const bar = this.#bars[row];
        const ratio = Math.min(1, Math.max(0, bar.downloaded / bar.total));
        const percent = Math.round(ratio * 100);
        const elapsedMs = bar.startTime > 0 ? Date.now() - bar.startTime : 0;
        const rate = elapsedMs > 0 ? bar.downloaded / elapsedMs : 0; // bytes/ms
        const etaSec = rate > 0 ? (bar.total - bar.downloaded) / rate / 1000 : 0;
        const width = 20;
        const completeCount = Math.round(width * ratio);
        const barStr = '='.repeat(completeCount) + ' '.repeat(width - completeCount);
        const status = ratio >= 1 ? 'unpacking' : `${percent}% ${etaSec.toFixed(1)}s`;
        return `${bar.title} [${barStr}] ${status} `;
    }
    // Invariant: cursor is at col 0 of the bottom row before and after this call.
    // Single top-down pass: go up to bar 0, render each bar, come back to bottom.
    #renderAll() {
        if (!this.#stream.isTTY) {
            return;
        }
        const N = this.#totalRows;
        if (N === 0) {
            return;
        }
        // Move cursor to top of bar area.
        if (N > 1) {
            this.#stream.moveCursor(0, -(N - 1));
        }
        for (let row = 0; row < N; row++) {
            const rendered = this.#computeRendered(row);
            if (rendered !== this.#bars[row].lastRendered) {
                this.#stream.cursorTo(0);
                this.#stream.write(rendered);
                this.#stream.clearLine(1);
                this.#bars[row].lastRendered = rendered;
            }
            if (row < N - 1) {
                this.#stream.moveCursor(0, 1);
            }
        }
        // Park cursor at col 0 of the bottom row.
        this.#stream.cursorTo(0);
        if (this.#allDone) {
            activeBar = null;
            this.#stream.write('\n');
        }
    }
    #onBarDone() {
        this.#doneCount++;
        if (this.#doneCount >= this.#totalRows && this.#totalRows > 0) {
            this.#allDone = true;
            // Don't emit \n here — the pending render microtask hasn't run yet.
            // #renderAll() will emit it after the final pass so the cursor is
            // already past the last bar line before the newline moves it.
        }
    }
}
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