package core

import (
	"errors"
	"os"
	"strings"

	"github.com/rwinkhart/go-boilerplate/back"
	"github.com/rwinkhart/libmutton/crypt"
	"github.com/rwinkhart/libmutton/global"
	"github.com/rwinkhart/libmutton/synccommon"
)

// WriteEntry writes entryData to an encrypted file at targetLocation.
func WriteEntry(targetLocation string, decBytes []byte) error {
	err := os.WriteFile(targetLocation, crypt.EncryptBytes(decBytes), 0600)
	if err != nil {
		return errors.New("unable to write to file: " + err.Error())
	}
	return nil
}

// EntryRefresh re-encrypts all libmutton entries with a new passphrase
// and optimizes each entry to ensure they are as slim as possible.
// This includes stripping trailing whitespace/newlines/carriage returns
// from each field and running each note through ClampTrailingWhitespace
// to ensure each note line is optimized as possible without breaking
// Markdown formatting.
func EntryRefresh(oldRCWPassphrase, newRCWPassphrase []byte, removeOldDir bool) error {
	// ensure global.EntryRoot+"-new" and global.EntryRoot-"old" do not exist
	dirEnds := []string{"-new", "-old"}
	for i, dirEnd := range dirEnds {
		if i == 1 && !removeOldDir {
			if _, err := os.Stat(global.EntryRoot + dirEnd); !os.IsNotExist(err) {
				return errors.New("unable to refresh entries: \"" + global.EntryRoot + dirEnd + "\" already exists")
			}
		}
		os.RemoveAll(global.EntryRoot + dirEnd)
	}

	// create output directory structure (global.EntryRoot + "-new"/*)
	entries, folders, err := synccommon.WalkEntryDir()
	if err != nil {
		return errors.New("unable to walk entry directory: " + err.Error())
	}
	for _, folder := range folders {
		fullPath := global.EntryRoot + "-new" + strings.ReplaceAll(folder, "/", global.PathSeparator)
		err := os.MkdirAll(fullPath, 0700)
		if err != nil {
			return errors.New("unable to create temporary directory \"" + fullPath + "\": " + err.Error())
		}
	}

	// decrypt, optimize, and re-encrypt each entry
	for _, entry := range entries {
		decryptedEntry, err := crypt.DecryptFileToSlice(global.TargetLocationFormat(entry))
		if err != nil {
			return err
		}
		// strip trailing whitespace...
		fieldsMain := decryptedEntry[:4]
		fieldsNote := back.RemoveTrailingEmptyStrings(decryptedEntry[4:])
		// ...from each non-note field
		for i, line := range fieldsMain {
			fieldsMain[i] = strings.TrimRight(line, " \t\r\n")
		}
		// ...and from each note line (preserve Markdown formatting)
		ClampTrailingWhitespace(fieldsNote)

		// re-combine fields
		decryptedEntry = append(fieldsMain, fieldsNote...)

		// write the entry to the new directory
		WriteEntry(global.EntryRoot+"-new"+strings.ReplaceAll(entry, "/", global.PathSeparator), []byte(strings.Join(decryptedEntry, "\n")))
	}

	return nil
}

// ClampTrailingWhitespace strips trailing newlines, carriage returns, and tabs from each line in a note.
// Additionally, it removes single trailing spaces and truncates multiple trailing spaces to two (for Markdown formatting).
func ClampTrailingWhitespace(note []string) {
	for i, line := range note {
		// remove trailing tabs, carriage returns, and newlines
		line = strings.TrimRight(line, "\t\r\n")

		// determine the number of trailing spaces in the trimmed line
		var endSpacesCount int
		for j := len(line) - 1; j >= 0; j-- {
			if line[j] != ' ' {
				break
			}
			endSpacesCount++
		}

		// remove single spaces, truncate multiple spaces (leave two for Markdown formatting)
		switch endSpacesCount {
		case 0:
			// no trailing spaces
			note[i] = line
		case 1:
			// remove the single trailing space
			note[i] = strings.TrimRight(line, " ")
		default:
			// truncate the trailing spaces to two
			note[i] = line[:len(line)-endSpacesCount+2]
		}
	}
}

// EntryAddPrecheck ensures the directory meant to contain a new
// entry exists and that the target entry location is not already used.
// Returns: statusCode (0 = success, 1 = target location already exists, 2 = containing directory is invalid).
func EntryAddPrecheck(targetLocation string) (uint8, error) {
	// ensure target location does not already exist
	_, isAccessible := back.TargetIsFile(targetLocation, false, 0)
	if isAccessible {
		return 1, errors.New("target location already exists")
	}
	// ensure target containing directory exists and is a directory (not a file)
	containingDir := targetLocation[:strings.LastIndex(targetLocation, global.PathSeparator)]
	isFile, isAccessible := back.TargetIsFile(containingDir, false, 1)
	if isFile || !isAccessible {
		return 2, errors.New("\"" + containingDir + "\" is not a valid containing directory")
	}
	return 0, nil
}

// EntryIsNotEmpty iterates through entryData and returns true if any line is not empty.
func EntryIsNotEmpty(entryData []string) bool {
	for _, line := range entryData {
		if line != "" {
			return true
		}
	}
	return false
}