#!/usr/bin/env bash

_render_wasm_lock_source=${BASH_SOURCE[0]}
_render_wasm_lock_dir=${_render_wasm_lock_source%/*}
if [[ "$_render_wasm_lock_dir" == "$_render_wasm_lock_source" ]]; then
    _render_wasm_lock_dir="."
fi
_RENDER_WASM_LOCK_DIR=$(cd -- "$_render_wasm_lock_dir" && pwd)
_RENDER_WASM_BUILD_LOCK_HELD=0

release_build_lock() {
    if [[ "$_RENDER_WASM_BUILD_LOCK_HELD" == "1" ]]; then
        _RENDER_WASM_BUILD_LOCK_HELD=0
        flock --unlock 9 2>/dev/null || true
    fi

    exec 9>&-
}

acquire_build_lock() {
    if ! command -v flock > /dev/null 2>&1; then
        echo "ERROR: render-wasm builds require flock from util-linux on Linux" >&2
        return 1
    fi

    if [[ "$_RENDER_WASM_BUILD_LOCK_HELD" == "1" ]]; then
        return 0
    fi

    local lock_file="${RENDER_WASM_LOCK_FILE:-$_RENDER_WASM_LOCK_DIR/.render-wasm-build.lock}"

    if ! exec 9>> "$lock_file"; then
        echo "ERROR: cannot open render-wasm build lock: $lock_file" >&2
        return 1
    fi

    trap 'release_build_lock' EXIT
    trap 'release_build_lock; exit 129' HUP
    trap 'release_build_lock; exit 130' INT
    trap 'release_build_lock; exit 131' QUIT
    trap 'release_build_lock; exit 143' TERM

    if ! flock --exclusive --nonblock 9; then
        echo "Waiting for another render-wasm build to finish: $lock_file" >&2
        if ! flock --exclusive 9; then
            echo "ERROR: cannot acquire render-wasm build lock: $lock_file" >&2
            release_build_lock
            return 1
        fi
    fi

    _RENDER_WASM_BUILD_LOCK_HELD=1
}