package meta4ra

import (
	"bytes"
	"io"
	"log"
	"os/exec"
	"strings"
	"sync"
)

// Sorted by preference order.
var HashesDefault = []string{
	"blake3-256:b3sum",
	"skein-512:skein512",
	"skein-256:skein256",
	"shake128:goshake128",
	"shake256:goshake256",
	"sha-512:sha512",
	"sha-256:sha256",
	"streebog-256:streebog256sum",
	"streebog-512:streebog512sum",
}

type Hasher struct {
	Names []string
	Cmds  []*exec.Cmd
	Ins   []io.WriteCloser
	Outs  []io.ReadCloser
	wg    sync.WaitGroup
}

func NewHasher(hashes string) *Hasher {
	h := Hasher{}
	for _, hc := range strings.Split(hashes, ",") {
		cols := strings.SplitN(hc, ":", 2)
		name, cmdline := cols[0], cols[1]
		cmd := exec.Command(cmdline)
		in, err := cmd.StdinPipe()
		if err != nil {
			log.Fatalln(err)
		}
		out, err := cmd.StdoutPipe()
		if err != nil {
			log.Fatalln(err)
		}
		h.Names = append(h.Names, name)
		h.Ins = append(h.Ins, in)
		h.Outs = append(h.Outs, out)
		h.Cmds = append(h.Cmds, cmd)
	}
	return &h
}

func (h *Hasher) Start() {
	for _, cmd := range h.Cmds {
		if err := cmd.Start(); err != nil {
			log.Fatalln(err)
		}
	}
}

func (h *Hasher) Write(p []byte) (n int, err error) {
	h.wg.Add(len(h.Names))
	for _, in := range h.Ins {
		go func(in io.WriteCloser) {
			if _, err := io.Copy(in, bytes.NewReader(p)); err != nil {
				log.Fatalln(err)
			}
			h.wg.Done()
		}(in)
	}
	h.wg.Wait()
	return len(p), nil
}

func (h *Hasher) Sums() []Hash {
	sums := make([]Hash, 0, len(h.Names))
	for i, name := range h.Names {
		if err := h.Ins[i].Close(); err != nil {
			log.Fatalln(err)
		}
		dgst, err := io.ReadAll(h.Outs[i])
		if err != nil {
			log.Fatalln(err)
		}
		sums = append(sums, Hash{Type: name, Hash: string(dgst[:len(dgst)-1])})
		if err = h.Cmds[i].Wait(); err != nil {
			log.Fatalln(err)
		}
	}
	return sums
}