packages.go

package apk

import (
	"bufio"
	"os"
	"reflect"
	"strconv"
	"strings"
	"time"
)

// Packages holds a series of packages, as described in an APKINDEX file
type Packages []*Package

// ReadPackages takes an APKINDEX files and parses the individual files contained
// therein
func ReadPackages(fn string) (p Packages, err error) {
	var (
		sb  strings.Builder
		pkg *Package
	)

	p = make(Packages, 0)

	f, err := os.Open(fn) // #nosec: G304
	if err != nil {
		return
	}

	defer f.Close() // #nosec: G307

	scanner := bufio.NewScanner(f)

	for scanner.Scan() {
		line := scanner.Text()
		if line == "" {
			pkg, err = DecodePackage(sb.String())
			if err != nil {
				return
			}

			p = append(p, pkg)
			sb.Reset()

			continue
		}

		sb.WriteString(line)
		sb.WriteString("\n")
	}

	// decode final
	pkg, err = DecodePackage(sb.String())
	if err != nil {
		return
	}

	p = append(p, pkg)

	err = scanner.Err()

	return
}

// Package represents a package from the Index file
// Keys and names and stuff are taken from
// https://github.com/alpinelinux/apk-tools/blob/da8d83338b7daa2bbd2e940f94d6515d69568800/src/apk_adb.c#L56-L76
type Package struct {
	ID            string    `apk:"C"`
	Name          string    `apk:"P"`
	Version       string    `apk:"V"`
	Description   string    `apk:"T"`
	URL           string    `apk:"U"`
	InstalledSize int       `apk:"I"`
	FileSize      int       `apk:"S"`
	Licence       string    `apk:"L"`
	Arch          string    `apk:"A"`
	Dependencies  []string  `apk:"D"`
	InstallIf     string    `apk:"i"`
	Provides      []string  `apk:"p"`
	Origin        string    `apk:"o"`
	Maintainer    string    `apk:"m"`
	BuildTime     time.Time `apk:"t"`
	RepoCommit    string    `apk:"c"`
	Replaces      string    `apk:"r"`
	Priority      int       `apk:"k"`
}

// DecodePackage takes a block of text and tries to decode a
// package from it
func DecodePackage(in string) (*Package, error) {
	p := &Package{}

	kvs := kv(in)

	ev := reflect.Indirect(reflect.ValueOf(p))
	et := ev.Type()

	for i := 0; i < et.NumField(); i++ {
		field, val := et.Field(i), ev.Field(i)

		key, ok := field.Tag.Lookup("apk")
		if !ok {
			continue
		}

		setVal, ok := kvs[key]
		if !ok {
			continue
		}

		switch tt := field.Type.String(); tt {
		case "string":
			val.SetString(setVal)

		case "[]string":
			val.Set(reflect.ValueOf(strings.Fields(setVal)))

		case "time.Time", "Time":
			i, err := strconv.Atoi(setVal)
			if err != nil {
				return p, err
			}

			val.Set(reflect.ValueOf(time.Unix(int64(i), 0)))

		case "int":
			i, err := strconv.Atoi(setVal)
			if err != nil {
				return p, err
			}

			val.SetInt(int64(i))

		default:
			continue
		}
	}

	return p, nil
}

func kv(in string) (out map[string]string) {
	out = make(map[string]string)

	for _, line := range strings.Split(in, "\n") {
		elems := strings.SplitN(line, ":", 2)
		if elems == nil {
			continue
		}

		if len(elems) != 2 {
			continue
		}

		out[elems[0]] = elems[1]
	}

	return
}