package sync

import (
	"bufio"
	"crypto"
	"encoding/hex"
	"fmt"
	"io"
	"os"
	"path"
	"strings"

	"srs.epita.fr/fic-server/libfic"

	_ "golang.org/x/crypto/blake2b"
)

func SyncExerciceHints(i Importer, exercice fic.Exercice) (errs []string) {
	params, err := parseExerciceParams(i, exercice.Path)
	if err != nil {
		errs = append(errs, fmt.Sprintf("%q: defines.txt: %s", path.Base(exercice.Path), err))
	}

	if _, err := exercice.WipeHints(); err != nil {
		errs = append(errs, err.Error())
	} else if ! i.exists(path.Join(exercice.Path, "hints")) {
		return
	} else if hints, err := i.listDir(path.Join(exercice.Path, "hints")); err != nil {
		errs = append(errs, err.Error())
	} else {
		for n, hfile := range hints {
			// Find corresponding parameters
			var hint_title = fmt.Sprintf("Astuce #%d", n + 1)
			var hint_cost = exercice.Gain / 4
			for _, hp := range params.Hints {
				if hp.Filename == hfile {
					if hp.Cost > 0 {
						hint_cost = hp.Cost
					}
					if hp.Title != "" {
						hint_title = hp.Title
					}
					break
				}
			}

			// Extract hint content
			var hint_cnt string

			if fi, err := i.stat(path.Join(exercice.Path, "hints", hfile)); err != nil {
				errs = append(errs, fmt.Sprintf("%q: unable to add hint %q: %s", path.Base(exercice.Path), hfile, err))
			} else if ! fi.IsDir() && fi.Size() > 512 {
				// Handle big files as downloadable content
				if res, err := i.importFile(path.Join(exercice.Path, "hints", hfile), func(filePath string, origin string) (interface{}, error) {
					// Calculate hash
					hash512 := crypto.BLAKE2b_512.New()
					if fd, err := os.Open(filePath); err != nil {
						return nil, err
					} else {
						defer fd.Close()

						reader := bufio.NewReader(fd)
						if _, err := io.Copy(hash512, reader); err != nil {
							return nil, err
						}
					}
					result512 := hash512.Sum(nil)

					return "$FILES" + hex.EncodeToString(result512) + strings.TrimPrefix(filePath, fic.FilesDir), nil
				}); err != nil {
					errs = append(errs, fmt.Sprintf("%q: unable to import hint file %q: %s", path.Base(exercice.Path), hfile, err))
					continue
				} else if s, ok := res.(string); !ok {
					errs = append(errs, fmt.Sprintf("%q: unable to import hint file %q: invalid string returned as filename", path.Base(exercice.Path), hfile))
					continue
				} else {
					hint_cnt = s
				}
			} else if hint_cnt, err = getFileContent(i, path.Join(exercice.Path, "hints", hfile)); err != nil {
				errs = append(errs, fmt.Sprintf("%q: unable to read hint file %q: %s", path.Base(exercice.Path), hfile, err))
				continue
			}

			// Import hint
			if _, err := exercice.AddHint(hint_title, hint_cnt, hint_cost); err != nil {
				errs = append(errs, fmt.Sprintf("%q: unable to add hint %q: %s", path.Base(exercice.Path), hfile, err))
			}
		}
	}
	return
}