/*
goredo -- redo implementation on pure Go
Copyright (C) 2020 Sergey Matveev <stargrave@stargrave.org>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, version 3 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

// Jobserver

package main

import "os"

var (
	JSR *os.File
	JSW *os.File
)

func jsInit() {
	jsrRaw := os.Getenv(RedoJSRFdEnv)
	jswRaw := os.Getenv(RedoJSWFdEnv)
	if (jsrRaw == "" && jswRaw != "") || (jsrRaw != "" && jswRaw == "") {
		panic("both JSR and JSW must be set")
	}
	if jsrRaw == "NO" {
		// infinite jobs
		return
	}
	if jsrRaw != "" {
		JSR = mustParseFd(jsrRaw, "JSR")
		JSW = mustParseFd(jswRaw, "JSW")
		jsRelease("ifchange entered")
		return
	}
	if *JobsN == 0 {
		// infinite jobs
		return
	}
	var err error
	JSR, JSW, err = os.Pipe()
	if err != nil {
		panic(err)
	}
	for i := uint(0); i < *JobsN; i++ {
		jsRelease("initial fill")
	}
}

func jsRelease(ctx string) {
	if JSW == nil {
		return
	}
	trace(CJS, "release from %s", ctx)
	if n, err := JSW.Write([]byte{0}); err != nil || n != 1 {
		panic("can not write JSW")
	}
}

func jsAcquire(ctx string) {
	if JSR == nil {
		return
	}
	trace(CJS, "acquire for %s", ctx)
	if n, err := JSR.Read([]byte{0}); err != nil || n != 1 {
		panic("can not read JSR")
	}
	trace(CJS, "acquired for %s", ctx)
}