package selfupdate

import (
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"io"
	"net/http"
	"os"
	"strings"
)

func download(client *http.Client, url, dst string) error {
	req, err := http.NewRequest(http.MethodGet, url, nil)
	if err != nil {
		return err
	}
	req.Header.Set("User-Agent", "eeco-update/1")
	resp, err := client.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("http %d", resp.StatusCode)
	}
	tmp, err := os.CreateTemp(parentDir(dst), ".eeco-dl-*")
	if err != nil {
		return err
	}
	tmpName := tmp.Name()
	if _, err := io.Copy(tmp, resp.Body); err != nil {
		tmp.Close()
		os.Remove(tmpName)
		return err
	}
	if err := tmp.Close(); err != nil {
		os.Remove(tmpName)
		return err
	}
	return os.Rename(tmpName, dst)
}

func parentDir(path string) string {
	i := strings.LastIndexAny(path, `/\`)
	if i < 0 {
		return "."
	}
	return path[:i]
}

func sha256File(path string) (string, error) {
	f, err := os.Open(path)
	if err != nil {
		return "", err
	}
	defer f.Close()
	h := sha256.New()
	if _, err := io.Copy(h, f); err != nil {
		return "", err
	}
	return hex.EncodeToString(h.Sum(nil)), nil
}

// checksumFor reads sumsPath (the `shasum -a 256` SHA256SUMS file) and
// returns the recorded hash for archiveBasename. Each line is:
//
//	<64-hex>  <basename>
//
// (two spaces between, per shasum's default text mode).
func checksumFor(sumsPath, archiveBasename string) (string, error) {
	b, err := os.ReadFile(sumsPath)
	if err != nil {
		return "", err
	}
	for _, raw := range strings.Split(string(b), "\n") {
		line := strings.TrimSpace(raw)
		if line == "" {
			continue
		}
		fields := strings.Fields(line)
		if len(fields) < 2 {
			continue
		}
		hash := fields[0]
		name := strings.TrimPrefix(fields[len(fields)-1], "*")
		if name == archiveBasename {
			if len(hash) != 64 {
				return "", fmt.Errorf("SHA256SUMS: bad hash for %s", archiveBasename)
			}
			return strings.ToLower(hash), nil
		}
	}
	return "", fmt.Errorf("SHA256SUMS: no entry for %s", archiveBasename)
}