package sync

import (
	"bufio"
	"encoding/hex"
	"fmt"
	"path"
	"strings"
	"unicode"

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

func buildFilesListInto(i Importer, exercice fic.Exercice, into string) (files []string, digests map[string][]byte, errs []string) {
	// If no files directory, don't display error
	if !i.exists(path.Join(exercice.Path, into)) {
		return
	}

	// Parse DIGESTS.txt
	if digs, err := getFileContent(i, path.Join(exercice.Path, into, "DIGESTS.txt")); err != nil {
		errs = append(errs, fmt.Sprintf("%q: unable to read DIGESTS.txt: %s", path.Base(exercice.Path), err))
	} else {
		digests = map[string][]byte{}
		for nline, d := range strings.Split(digs, "\n") {
			if dsplt := strings.SplitN(d, " ", 2); len(dsplt) < 2 {
				errs = append(errs, fmt.Sprintf("%q: unable to parse DIGESTS.txt line %d: invalid format", path.Base(exercice.Path), nline+1))
				continue
			} else if hash, err := hex.DecodeString(dsplt[0]); err != nil {
				errs = append(errs, fmt.Sprintf("%q: unable to parse DIGESTS.txt line %d: %s", path.Base(exercice.Path), nline+1, err))
				continue
			} else {
				digests[strings.TrimFunc(dsplt[1], unicode.IsSpace)] = hash
			}
		}
	}

	// Read file list
	if flist, err := i.listDir(path.Join(exercice.Path, into)); err != nil {
		errs = append(errs, err.Error())
	} else {
		for _, fname := range flist {
			if fname == "DIGESTS.txt" {
				continue
			}

			if matched, _ := path.Match("*.00", fname); matched {
				fname = fname[:len(fname)-3]
			} else if matched, _ := path.Match("*00", fname); matched {
				fname = fname[:len(fname)-2]
			} else if matched, _ := path.Match("*_MERGED", fname); matched {
				continue
			}

			fileFound := false
			for _, f := range files {
				if fname == f {
					fileFound = true
					break
				}
			}

			if !fileFound {
				files = append(files, fname)
			}
		}
	}

	return
}

// CheckExerciceFiles checks that remote files have the right digest.
func CheckExerciceFiles(i Importer, exercice fic.Exercice) (files []fic.EFile, errs []string) {
	flist, digests, berrs := buildFilesListInto(i, exercice, "files")
	errs = append(errs, berrs...)

	for _, fname := range flist {
		w, hash160, hash512 := fic.CreateHashBuffers()

		if err := i.getFile(path.Join(exercice.Path, "files", fname), bufio.NewWriter(w)); err != nil {
			errs = append(errs, fmt.Sprintf("%q: unable to read file %q: %s", path.Base(exercice.Path), fname, err))
			continue
		} else if _, err := fic.CheckBufferHash(hash160, hash512, digests[fname]); err != nil {
			errs = append(errs, fmt.Sprintf("%q: %s: %s", path.Base(exercice.Path), fname, err))
		}

		files = append(files, fic.EFile{Name: fname})
	}
	return
}

// SyncExerciceFiles reads the content of files/ directory and import it as EFile for the given challenge.
// It takes care of DIGESTS.txt and ensure imported files match.
func SyncExerciceFiles(i Importer, exercice fic.Exercice) (errs []string) {
	if _, err := exercice.WipeFiles(); err != nil {
		errs = append(errs, err.Error())
	}

	files, digests, berrs := buildFilesListInto(i, exercice, "files")
	errs = append(errs, berrs...)

	// Import standard files
	for _, fname := range files {
		if f, err := i.importFile(path.Join(exercice.Path, "files", fname),
			func(filePath string, origin string) (interface{}, error) {
				return exercice.ImportFile(filePath, origin, digests[fname])
			}); err != nil {
			errs = append(errs, fmt.Sprintf("%q: unable to import file %q: %s", path.Base(exercice.Path), fname, err))
			continue
		} else if f.(fic.EFile).Size == 0 {
			errs = append(errs, fmt.Sprintf("%q: WARNING imported file %q is empty!", path.Base(exercice.Path), fname))
		}
	}
	return
}