package sync

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

	"github.com/gin-gonic/gin"

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

func BuildFilesListInto(i Importer, exercice *fic.Exercice, into string) (files []string, digests map[string][]byte, errs []error) {
	// 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, NewExerciceError(exercice, fmt.Errorf("unable to read %s: %w", path.Join(into, "DIGESTS.txt"), 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, NewExerciceError(exercice, fmt.Errorf("unable to parse %s line %d: invalid format", path.Join(into, "DIGESTS.txt"), nline+1)))
				continue
			} else if hash, err := hex.DecodeString(dsplt[0]); err != nil {
				errs = append(errs, NewExerciceError(exercice, fmt.Errorf("unable to parse %s line %d: %w", path.Join(into, "DIGESTS.txt"), 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, NewExerciceError(exercice, err))
	} else {
		for _, fname := range flist {
			if fname == "DIGESTS.txt" || fname == ".gitattributes" {
				continue
			}

			if matched, _ := path.Match("*.[0-9][0-9]", fname); matched {
				fname = fname[:len(fname)-3]
			} else if matched, _ := path.Match("*[0-9][0-9]", 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
}

// CheckExerciceFilesPresence limits remote checks to presence, don't get it to check digest.
func CheckExerciceFilesPresence(i Importer, exercice *fic.Exercice) (files []string, errs []error) {
	flist, digests, berrs := BuildFilesListInto(i, exercice, "files")
	errs = append(errs, berrs...)

	for _, fname := range flist {
		if !i.exists(path.Join(exercice.Path, "files", fname)) {
			errs = append(errs, NewFileError(exercice, fname, fmt.Errorf("No such file or directory")))
		} else if _, ok := digests[fname]; !ok {
			errs = append(errs, NewFileError(exercice, fname, fmt.Errorf("unable to import file: No digest given")))
		} else {
			files = append(files, fname)
		}
	}

	for fname := range digests {
		if !i.exists(path.Join(exercice.Path, "files", fname)) {
			errs = append(errs, NewFileError(exercice, fname, fmt.Errorf("unable to read file: No such file or directory. Check your DIGESTS.txt for legacy entries.")))
		}
	}

	return
}

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

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

		if err := GetFile(i, path.Join(exercice.Path, "files", fname), bufio.NewWriter(w)); err != nil {
			errs = append(errs, NewFileError(exercice, fname, fmt.Errorf("unable to read file: %w", err)))
			continue
		} else if _, err := fic.CheckBufferHash(hash160, hash512, digests[fname]); err != nil {
			errs = append(errs, NewFileError(exercice, fname, err))
		} else if size, err := getFileSize(i, path.Join(exercice.Path, "files", fname)); err != nil {
			errs = append(errs, NewFileError(exercice, fname, err))
		} else {
			file := exercice.NewDummyFile(path.Join(exercice.Path, "files", fname), getDestinationFilePath(path.Join(exercice.Path, "files", fname)), (*hash512).Sum(nil), size)

			// Call checks hooks
			for _, h := range hooks.fileHooks {
				for _, e := range h(file, exceptions) {
					errs = append(errs, NewFileError(exercice, fname, e))
				}
			}
		}

		files = append(files, 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, exceptions *CheckExceptions) (errs []error) {
	if _, err := exercice.WipeFiles(); err != nil {
		errs = append(errs, err)
	}

	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) {
				var digest_shown []byte
				if strings.HasSuffix(fname, ".gz") {
					if d, exists := digests[strings.TrimSuffix(fname, ".gz")]; exists {
						digest_shown = d
					}
				}
				return exercice.ImportFile(filePath, origin, digests[fname], digest_shown)
			}); err != nil {
			errs = append(errs, NewFileError(exercice, fname, err))
			continue
		} else if f.(*fic.EFile).Size == 0 {
			errs = append(errs, NewFileError(exercice, fname, fmt.Errorf("imported file is empty!")))
		} else {
			// Call checks hooks
			for _, h := range hooks.fileHooks {
				for _, e := range h(f.(*fic.EFile), exceptions) {
					errs = append(errs, NewFileError(exercice, fname, e))
				}
			}
		}
	}
	return
}

// ApiGetRemoteExerciceFiles is an accessor to remote exercice files list.
func ApiGetRemoteExerciceFiles(c *gin.Context) {
	theme, exceptions, errs := BuildTheme(GlobalImporter, c.Params.ByName("thid"))
	if theme != nil {
		exercice, _, _, _, errs := BuildExercice(GlobalImporter, theme, path.Join(theme.Path, c.Params.ByName("exid")), nil, exceptions)
		if exercice != nil {
			files, digests, errs := BuildFilesListInto(GlobalImporter, exercice, "files")
			if files != nil {
				var ret []*fic.EFile
				for _, fname := range files {
					fPath := path.Join(exercice.Path, "files", fname)
					fSize, _ := getFileSize(GlobalImporter, fPath)
					ret = append(ret, &fic.EFile{
						Path:     fPath,
						Name:     fname,
						Checksum: digests[fname],
						Size:     fSize,
					})
				}
				c.JSON(http.StatusOK, ret)
			} else {
				c.AbortWithStatusJSON(http.StatusBadRequest, gin.H{"errmsg": fmt.Errorf("%q", errs)})
				return
			}
		} else {
			c.AbortWithStatusJSON(http.StatusBadRequest, gin.H{"errmsg": fmt.Errorf("%q", errs)})
			return
		}
	} else {
		c.AbortWithStatusJSON(http.StatusBadRequest, gin.H{"errmsg": fmt.Errorf("%q", errs)})
		return
	}
}