// Copyright 2018 The Go Authors. All rights reserved.

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

// +build ignore

// Generate system call table for DragonFly, NetBSD,

// FreeBSD, OpenBSD or Darwin from master list

// (for example, /usr/src/sys/kern/syscalls.master or

// sys/syscall.h).

package main

import (

	"bufio"

	"fmt"

	"io"

	"io/ioutil"

	"net/http"

	"os"

	"regexp"

	"strings"

)

var (

	goos, goarch string

)

// cmdLine returns this programs's commandline arguments

func cmdLine() string {

	return "go run mksysnum.go " + strings.Join(os.Args[1:], " ")

}

// buildTags returns build tags

func buildTags() string {

	return fmt.Sprintf("%s,%s", goarch, goos)

}

func checkErr(err error) {

	if err != nil {

		fmt.Fprintf(os.Stderr, "%v\n", err)

		os.Exit(1)

	}

}

// source string and substring slice for regexp

type re struct {

	str string   // source string

	sub []string // matched sub-string

}

// Match performs regular expression match

func (r *re) Match(exp string) bool {

	r.sub = regexp.MustCompile(exp).FindStringSubmatch(r.str)

	if r.sub != nil {

		return true

	}

	return false

}

// fetchFile fetches a text file from URL

func fetchFile(URL string) io.Reader {

	resp, err := http.Get(URL)

	checkErr(err)

	defer resp.Body.Close()

	body, err := ioutil.ReadAll(resp.Body)

	checkErr(err)

	return strings.NewReader(string(body))

}

// readFile reads a text file from path

func readFile(path string) io.Reader {

	file, err := os.Open(os.Args[1])

	checkErr(err)

	return file

}

func format(name, num, proto string) string {

	name = strings.ToUpper(name)

	// There are multiple entries for enosys and nosys, so comment them out.

	nm := re{str: name}

	if nm.Match(`^SYS_E?NOSYS$`) {

		name = fmt.Sprintf("// %s", name)

	}

	if name == `SYS_SYS_EXIT` {

		name = `SYS_EXIT`

	}

	return fmt.Sprintf("	%s = %s;  // %s\n", name, num, proto)

}

func main() {

	// Get the OS (using GOOS_TARGET if it exist)

	goos = os.Getenv("GOOS_TARGET")

	if goos == "" {

		goos = os.Getenv("GOOS")

	}

	// Get the architecture (using GOARCH_TARGET if it exists)

	goarch = os.Getenv("GOARCH_TARGET")

	if goarch == "" {

		goarch = os.Getenv("GOARCH")

	}

	// Check if GOOS and GOARCH environment variables are defined

	if goarch == "" || goos == "" {

		fmt.Fprintf(os.Stderr, "GOARCH or GOOS not defined in environment\n")

		os.Exit(1)

	}

	file := strings.TrimSpace(os.Args[1])

	var syscalls io.Reader

	if strings.HasPrefix(file, "https://") || strings.HasPrefix(file, "http://") {

		// Download syscalls.master file

		syscalls = fetchFile(file)

	} else {

		syscalls = readFile(file)

	}

	var text, line string

	s := bufio.NewScanner(syscalls)

	for s.Scan() {

		t := re{str: line}

		if t.Match(`^(.*)\\$`) {

			// Handle continuation

			line = t.sub[1]

			line += strings.TrimLeft(s.Text(), " \t")

		} else {

			// New line

			line = s.Text()

		}

		t = re{str: line}

		if t.Match(`\\$`) {

			continue

		}

		t = re{str: line}

		switch goos {

		case "dragonfly":

			if t.Match(`^([0-9]+)\s+STD\s+({ \S+\s+(\w+).*)$`) {

				num, proto := t.sub[1], t.sub[2]

				name := fmt.Sprintf("SYS_%s", t.sub[3])

				text += format(name, num, proto)

			}

		case "freebsd":

			if t.Match(`^([0-9]+)\s+\S+\s+(?:(?:NO)?STD|COMPAT10)\s+({ \S+\s+(\w+).*)$`) {

				num, proto := t.sub[1], t.sub[2]

				name := fmt.Sprintf("SYS_%s", t.sub[3])

				text += format(name, num, proto)

			}

		case "openbsd":

			if t.Match(`^([0-9]+)\s+STD\s+(NOLOCK\s+)?({ \S+\s+\*?(\w+).*)$`) {

				num, proto, name := t.sub[1], t.sub[3], t.sub[4]

				text += format(name, num, proto)

			}

		case "netbsd":

			if t.Match(`^([0-9]+)\s+((STD)|(NOERR))\s+(RUMP\s+)?({\s+\S+\s*\*?\s*\|(\S+)\|(\S*)\|(\w+).*\s+})(\s+(\S+))?$`) {

				num, proto, compat := t.sub[1], t.sub[6], t.sub[8]

				name := t.sub[7] + "_" + t.sub[9]

				if t.sub[11] != "" {

					name = t.sub[7] + "_" + t.sub[11]

				}

				name = strings.ToUpper(name)

				if compat == "" || compat == "13" || compat == "30" || compat == "50" {

					text += fmt.Sprintf("	%s = %s;  // %s\n", name, num, proto)

				}

			}

		case "darwin":

			if t.Match(`^#define\s+SYS_(\w+)\s+([0-9]+)`) {

				name, num := t.sub[1], t.sub[2]

				name = strings.ToUpper(name)

				text += fmt.Sprintf("	SYS_%s = %s;\n", name, num)

			}

		default:

			fmt.Fprintf(os.Stderr, "unrecognized GOOS=%s\n", goos)

			os.Exit(1)

		}

	}

	err := s.Err()

	checkErr(err)

	fmt.Printf(template, cmdLine(), buildTags(), text)

}

const template = `// %s

// Code generated by the command above; see README.md. DO NOT EDIT.

// +build %s

package unix

const(

%s)`