buffer.go

package buffer

import (
	"bufio"
	"bytes"
	"crypto/md5"
	"errors"
	"fmt"
	"io"
	"io/fs"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"time"

	luar "layeh.com/gopher-luar"

	"github.com/micro-editor/micro/v2/internal/config"
	ulua "github.com/micro-editor/micro/v2/internal/lua"
	"github.com/micro-editor/micro/v2/internal/screen"
	"github.com/micro-editor/micro/v2/internal/util"
	"github.com/micro-editor/micro/v2/pkg/highlight"
	dmp "github.com/sergi/go-diff/diffmatchpatch"
	"golang.org/x/text/encoding"
	"golang.org/x/text/encoding/htmlindex"
	"golang.org/x/text/encoding/unicode"
	"golang.org/x/text/transform"
)

var (
	// OpenBuffers is a list of the currently open buffers
	OpenBuffers []*Buffer
	// LogBuf is a reference to the log buffer which can be opened with the
	// `> log` command
	LogBuf *Buffer
)

// The BufType defines what kind of buffer this is
type BufType struct {
	Kind     int
	Readonly bool // The buffer cannot be edited
	Scratch  bool // The buffer cannot be saved
	Syntax   bool // Syntax highlighting is enabled
}

var (
	// BTDefault is a default buffer
	BTDefault = BufType{0, false, false, true}
	// BTHelp is a help buffer
	BTHelp = BufType{1, true, true, true}
	// BTLog is a log buffer
	BTLog = BufType{2, true, true, false}
	// BTScratch is a buffer that cannot be saved (for scratch work)
	BTScratch = BufType{3, false, true, false}
	// BTRaw is a buffer that shows raw terminal events
	BTRaw = BufType{4, false, true, false}
	// BTInfo is a buffer for inputting information
	BTInfo = BufType{5, false, true, false}
	// BTStdout is a buffer that only writes to stdout
	// when closed
	BTStdout = BufType{6, false, true, true}
)

// SharedBuffer is a struct containing info that is shared among buffers
// that have the same file open
type SharedBuffer struct {
	*LineArray
	// Stores the last modification time of the file the buffer is pointing to
	ModTime time.Time
	// Type of the buffer (e.g. help, raw, scratch etc..)
	Type BufType

	// Path to the file on disk
	Path string
	// Absolute path to the file on disk
	AbsPath string
	// Name of the buffer on the status line
	name string

	toStdout bool

	// Settings customized by the user
	Settings map[string]any
	// LocalSettings customized by the user for this buffer only
	LocalSettings map[string]bool

	encoding encoding.Encoding

	Suggestions   []string
	Completions   []string
	CurSuggestion int

	Messages []*Message

	updateDiffTimer   *time.Timer
	diffBase          []byte
	diffBaseLineCount int
	diffLock          sync.RWMutex
	diff              map[int]DiffStatus

	forceKeepBackup bool

	// ReloadDisabled allows the user to disable reloads if they
	// are viewing a file that is constantly changing
	ReloadDisabled bool

	isModified bool
	// Whether or not suggestions can be autocompleted must be shared because
	// it changes based on how the buffer has changed
	HasSuggestions bool

	// The Highlighter struct actually performs the highlighting
	Highlighter *highlight.Highlighter
	// SyntaxDef represents the syntax highlighting definition being used
	// This stores the highlighting rules and filetype detection info
	SyntaxDef *highlight.Def

	ModifiedThisFrame bool

	// Hash of the original buffer -- empty if fastdirty is on
	origHash [md5.Size]byte
}

func (b *SharedBuffer) insert(pos Loc, value []byte) {
	b.HasSuggestions = false
	b.LineArray.insert(pos, value)
	b.setModified()

	inslines := bytes.Count(value, []byte{'\n'})
	b.MarkModified(pos.Y, pos.Y+inslines)
}

func (b *SharedBuffer) remove(start, end Loc) []byte {
	b.HasSuggestions = false
	defer b.setModified()
	defer b.MarkModified(start.Y, end.Y)
	return b.LineArray.remove(start, end)
}

func (b *SharedBuffer) setModified() {
	if b.Type.Scratch {
		return
	}

	if b.Settings["fastdirty"].(bool) {
		b.isModified = true
	} else {
		var buff [md5.Size]byte

		b.calcHash(&buff)
		b.isModified = buff != b.origHash
	}

	if b.isModified {
		b.RequestBackup()
	} else {
		b.CancelBackup()
	}
}

// calcHash calculates md5 hash of all lines in the buffer
func (b *SharedBuffer) calcHash(out *[md5.Size]byte) {
	h := md5.New()

	if len(b.lines) > 0 {
		h.Write(b.lines[0].data)

		for _, l := range b.lines[1:] {
			if b.Endings == FFDos {
				h.Write([]byte{'\r', '\n'})
			} else {
				h.Write([]byte{'\n'})
			}
			h.Write(l.data)
		}
	}

	h.Sum((*out)[:0])
}

// MarkModified marks the buffer as modified for this frame
// and performs rehighlighting if syntax highlighting is enabled
func (b *SharedBuffer) MarkModified(start, end int) {
	b.ModifiedThisFrame = true

	start = util.Clamp(start, 0, len(b.lines)-1)
	end = util.Clamp(end, 0, len(b.lines)-1)

	if b.Settings["syntax"].(bool) && b.SyntaxDef != nil {
		l := -1
		for i := start; i <= end; i++ {
			l = util.Max(b.Highlighter.ReHighlightStates(b, i), l)
		}
		b.Highlighter.HighlightMatches(b, start, l)
	}

	for i := start; i <= end; i++ {
		b.LineArray.invalidateSearchMatches(i)
	}
}

// DisableReload disables future reloads of this sharedbuffer
func (b *SharedBuffer) DisableReload() {
	b.ReloadDisabled = true
}

const (
	DSUnchanged    = 0
	DSAdded        = 1
	DSModified     = 2
	DSDeletedAbove = 3
)

type DiffStatus byte

type Command struct {
	StartCursor      Loc
	SearchRegex      string
	SearchAfterStart bool
}

var emptyCommand = Command{
	StartCursor:      Loc{-1, -1},
	SearchRegex:      "",
	SearchAfterStart: false,
}

// Buffer stores the main information about a currently open file including
// the actual text (in a LineArray), the undo/redo stack (in an EventHandler)
// all the cursors, the syntax highlighting info, the settings for the buffer
// and some misc info about modification time and path location.
// The syntax highlighting info must be stored with the buffer because the syntax
// highlighter attaches information to each line of the buffer for optimization
// purposes so it doesn't have to rehighlight everything on every update.
// Likewise for the search highlighting.
type Buffer struct {
	*EventHandler
	*SharedBuffer

	cursors     []*Cursor
	curCursor   int
	StartCursor Loc

	// OptionCallback is called after a buffer option value is changed.
	// The display module registers its OptionCallback to ensure the buffer window
	// is properly updated when needed. This is a workaround for the fact that
	// the buffer module cannot directly call the display's API (it would mean
	// a circular dependency between packages).
	OptionCallback func(option string, nativeValue any)

	// The display module registers its own GetVisualX function for getting
	// the correct visual x location of a cursor when softwrap is used.
	// This is hacky. Maybe it would be better to move all the visual x logic
	// from buffer to display, but it would require rewriting a lot of code.
	GetVisualX func(loc Loc) int

	// Last search stores the last successful search
	LastSearch      string
	LastSearchRegex bool
	// HighlightSearch enables highlighting all instances of the last successful search
	HighlightSearch bool

	// OverwriteMode indicates that we are in overwrite mode (toggled by
	// Insert key by default) i.e. that typing a character shall replace the
	// character under the cursor instead of inserting a character before it.
	OverwriteMode bool
}

// NewBufferFromFileWithCommand opens a new buffer with a given command
// If cmd.StartCursor is {-1, -1} the location does not overwrite what the cursor location
// would otherwise be (start of file, or saved cursor position if `savecursor` is
// enabled)
func NewBufferFromFileWithCommand(path string, btype BufType, cmd Command) (*Buffer, error) {
	var err error
	filename := path
	if config.GetGlobalOption("parsecursor").(bool) && cmd.StartCursor.X == -1 && cmd.StartCursor.Y == -1 {
		var cursorPos []string
		filename, cursorPos = util.GetPathAndCursorPosition(filename)
		cmd.StartCursor, err = ParseCursorLocation(cursorPos)
		if err != nil {
			cmd.StartCursor = Loc{-1, -1}
		}
	}

	filename, err = util.ReplaceHome(filename)
	if err != nil {
		return nil, err
	}

	fileInfo, serr := os.Stat(filename)
	if serr != nil && !errors.Is(serr, fs.ErrNotExist) {
		return nil, serr
	}
	if serr == nil && fileInfo.IsDir() {
		return nil, errors.New("Error: " + filename + " is a directory and cannot be opened")
	}
	if serr == nil && !fileInfo.Mode().IsRegular() {
		return nil, errors.New("Error: " + filename + " is not a regular file and cannot be opened")
	}

	f, err := os.OpenFile(filename, os.O_WRONLY, 0)
	readonly := errors.Is(err, fs.ErrPermission)
	f.Close()

	file, err := os.Open(filename)
	if err == nil {
		defer file.Close()
	}

	var buf *Buffer
	if errors.Is(err, fs.ErrNotExist) {
		// File does not exist -- create an empty buffer with that name
		buf = NewBufferFromString("", filename, btype)
	} else if err != nil {
		return nil, err
	} else {
		buf = NewBuffer(file, util.FSize(file), filename, btype, cmd)
		if buf == nil {
			return nil, errors.New("could not open file")
		}
	}

	if readonly && prompt != nil {
		prompt.Message(fmt.Sprintf("Warning: file is readonly - %s will be attempted when saving", config.GlobalSettings["sucmd"].(string)))
		// buf.SetOptionNative("readonly", true)
	}

	return buf, nil
}

// NewBufferFromFile opens a new buffer using the given path
// It will also automatically handle `~`, and line/column with filename:l:c
// It will return an empty buffer if the path does not exist
// and an error if the file is a directory
func NewBufferFromFile(path string, btype BufType) (*Buffer, error) {
	return NewBufferFromFileWithCommand(path, btype, emptyCommand)
}

// NewBufferFromStringWithCommand creates a new buffer containing the given string
// with a cursor loc and a search text
func NewBufferFromStringWithCommand(text, path string, btype BufType, cmd Command) *Buffer {
	return NewBuffer(strings.NewReader(text), int64(len(text)), path, btype, cmd)
}

// NewBufferFromString creates a new buffer containing the given string
func NewBufferFromString(text, path string, btype BufType) *Buffer {
	return NewBuffer(strings.NewReader(text), int64(len(text)), path, btype, emptyCommand)
}

// NewBuffer creates a new buffer from a given reader with a given path
// Ensure that ReadSettings and InitGlobalSettings have been called before creating
// a new buffer
// Places the cursor at startcursor. If startcursor is -1, -1 places the
// cursor at an autodetected location (based on savecursor or :LINE:COL)
func NewBuffer(r io.Reader, size int64, path string, btype BufType, cmd Command) *Buffer {
	absPath, err := filepath.Abs(path)
	if err != nil {
		absPath = path
	}

	b := new(Buffer)

	found := false
	if len(path) > 0 {
		for _, buf := range OpenBuffers {
			if buf.AbsPath == absPath && buf.Type != BTInfo {
				found = true
				b.SharedBuffer = buf.SharedBuffer
				b.EventHandler = buf.EventHandler
			}
		}
	}

	hasBackup := false
	if !found {
		b.SharedBuffer = new(SharedBuffer)
		b.Type = btype

		b.AbsPath = absPath
		b.Path = path

		b.Settings = config.DefaultCommonSettings()
		b.LocalSettings = make(map[string]bool)
		for k, v := range config.GlobalSettings {
			if _, ok := config.DefaultGlobalOnlySettings[k]; !ok {
				// make sure setting is not global-only
				b.Settings[k] = v
			}
		}
		config.UpdatePathGlobLocals(b.Settings, absPath)

		b.encoding, err = htmlindex.Get(b.Settings["encoding"].(string))
		if err != nil {
			b.encoding = unicode.UTF8
			b.Settings["encoding"] = "utf-8"
		}

		var ok bool
		hasBackup, ok = b.ApplyBackup(size)

		if !ok {
			return NewBufferFromString("", "", btype)
		}
		if !hasBackup {
			reader := bufio.NewReader(transform.NewReader(r, b.encoding.NewDecoder()))

			var ff FileFormat = FFAuto

			if size == 0 {
				// for empty files, use the fileformat setting instead of
				// autodetection
				switch b.Settings["fileformat"] {
				case "unix":
					ff = FFUnix
				case "dos":
					ff = FFDos
				}
			} else {
				// in case of autodetection treat as locally set
				b.LocalSettings["fileformat"] = true
			}

			b.LineArray = NewLineArray(uint64(size), ff, reader)
		}
		b.EventHandler = NewEventHandler(b.SharedBuffer, b.cursors)

		// The last time this file was modified
		b.UpdateModTime()
	}

	if b.Settings["readonly"].(bool) && b.Type == BTDefault {
		b.Type.Readonly = true
	}

	switch b.Endings {
	case FFUnix:
		b.Settings["fileformat"] = "unix"
	case FFDos:
		b.Settings["fileformat"] = "dos"
	}

	b.UpdateRules()
	// we know the filetype now, so update per-filetype settings
	config.UpdateFileTypeLocals(b.Settings, settingAsString(b.Settings["filetype"], "unknown"))

	if _, err := os.Stat(filepath.Join(config.ConfigDir, "buffers")); errors.Is(err, fs.ErrNotExist) {
		os.Mkdir(filepath.Join(config.ConfigDir, "buffers"), os.ModePerm)
	}

	if cmd.StartCursor.X != -1 && cmd.StartCursor.Y != -1 {
		b.StartCursor = cmd.StartCursor
	} else if b.Settings["savecursor"].(bool) || b.Settings["saveundo"].(bool) {
		err := b.Unserialize()
		if err != nil {
			screen.TermMessage(err)
		}
	}

	b.AddCursor(NewCursor(b, b.StartCursor))
	b.GetActiveCursor().Relocate()

	if cmd.SearchRegex != "" {
		match, found, _ := b.FindNext(cmd.SearchRegex, b.Start(), b.End(), b.StartCursor, true, true)
		if found {
			if cmd.SearchAfterStart {
				// Search from current cursor and move it accordingly
				b.GetActiveCursor().SetSelectionStart(match[0])
				b.GetActiveCursor().SetSelectionEnd(match[1])
				b.GetActiveCursor().OrigSelection[0] = b.GetActiveCursor().CurSelection[0]
				b.GetActiveCursor().OrigSelection[1] = b.GetActiveCursor().CurSelection[1]
				b.GetActiveCursor().GotoLoc(match[1])
			}
			b.LastSearch = cmd.SearchRegex
			b.LastSearchRegex = true
			b.HighlightSearch = b.Settings["hlsearch"].(bool)
		}
	}

	if !b.Settings["fastdirty"].(bool) && !found {
		if size > LargeFileThreshold {
			// If the file is larger than LargeFileThreshold fastdirty needs to be on
			b.Settings["fastdirty"] = true
		} else if !hasBackup {
			// since applying a backup does not save the applied backup to disk, we should
			// not calculate the original hash based on the backup data
			b.calcHash(&b.origHash)
		}
	}

	err = config.RunPluginFn("onBufferOpen", luar.New(ulua.L, b))
	if err != nil {
		screen.TermMessage(err)
	}

	OpenBuffers = append(OpenBuffers, b)

	return b
}

// CloseOpenBuffers removes all open buffers
func CloseOpenBuffers() {
	for i, buf := range OpenBuffers {
		buf.Fini()
		OpenBuffers[i] = nil
	}
	OpenBuffers = OpenBuffers[:0]
}

// Close removes this buffer from the list of open buffers
func (b *Buffer) Close() {
	for i, buf := range OpenBuffers {
		if b == buf {
			b.Fini()
			copy(OpenBuffers[i:], OpenBuffers[i+1:])
			OpenBuffers[len(OpenBuffers)-1] = nil
			OpenBuffers = OpenBuffers[:len(OpenBuffers)-1]
			return
		}
	}
}

// Fini should be called when a buffer is closed and performs
// some cleanup
func (b *Buffer) Fini() {
	if !b.Modified() {
		b.Serialize()
	}
	b.CancelBackup()

	if b.Type == BTStdout {
		fmt.Fprint(util.Stdout, string(b.Bytes()))
	}
}

// GetName returns the name that should be displayed in the statusline
// for this buffer
func (b *Buffer) GetName() string {
	name := b.name
	if name == "" {
		if b.Path == "" {
			return "No name"
		}
		name = b.Path
	}
	if b.Settings["basename"].(bool) {
		return filepath.Base(name)
	}
	return name
}

// SetName changes the name for this buffer
func (b *Buffer) SetName(s string) {
	b.name = s
}

// Insert inserts the given string of text at the start location
func (b *Buffer) Insert(start Loc, text string) {
	if !b.Type.Readonly {
		b.EventHandler.cursors = b.cursors
		b.EventHandler.active = b.curCursor
		b.EventHandler.Insert(start, text)
	}
}

// Remove removes the characters between the start and end locations
func (b *Buffer) Remove(start, end Loc) {
	if !b.Type.Readonly {
		b.EventHandler.cursors = b.cursors
		b.EventHandler.active = b.curCursor
		b.EventHandler.Remove(start, end)
	}
}

// FileType returns the buffer's filetype
func (b *Buffer) FileType() string {
	return settingAsString(b.Settings["filetype"], "unknown")
}

// ExternallyModified returns whether the file being edited has
// been modified by some external process
func (b *Buffer) ExternallyModified() bool {
	modTime, err := util.GetModTime(b.Path)
	if err == nil {
		return modTime != b.ModTime
	}
	return false
}

// UpdateModTime updates the modtime of this file
func (b *Buffer) UpdateModTime() (err error) {
	b.ModTime, err = util.GetModTime(b.Path)
	return
}

// ReOpen reloads the current buffer from disk
func (b *Buffer) ReOpen() error {
	file, err := os.Open(b.Path)
	if err != nil {
		return err
	}
	defer file.Close()

	enc, err := htmlindex.Get(b.Settings["encoding"].(string))
	if err != nil {
		return err
	}

	reader := bufio.NewReader(transform.NewReader(file, enc.NewDecoder()))
	data, err := io.ReadAll(reader)
	txt := string(data)

	if err != nil {
		return err
	}
	b.EventHandler.ApplyDiff(txt)

	err = b.UpdateModTime()
	if !b.Settings["fastdirty"].(bool) {
		if len(data) > LargeFileThreshold {
			b.Settings["fastdirty"] = true
		} else {
			b.calcHash(&b.origHash)
		}
	}
	b.isModified = false
	b.RelocateCursors()
	return err
}

// RelocateCursors relocates all cursors (makes sure they are in the buffer)
func (b *Buffer) RelocateCursors() {
	for _, c := range b.cursors {
		c.Relocate()
	}
}

// DeselectCursors removes selection from all cursors
func (b *Buffer) DeselectCursors() {
	for _, c := range b.cursors {
		c.Deselect(true)
	}
}

// RuneAt returns the rune at a given location in the buffer
func (b *Buffer) RuneAt(loc Loc) rune {
	line := b.LineBytes(loc.Y)
	if len(line) > 0 {
		i := 0
		for len(line) > 0 {
			r, _, size := util.DecodeCharacter(line)
			line = line[size:]

			if i == loc.X {
				return r
			}

			i++
		}
	}
	return '\n'
}

// WordAt returns the word around a given location in the buffer
func (b *Buffer) WordAt(loc Loc) []byte {
	if len(b.LineBytes(loc.Y)) == 0 || !util.IsWordChar(b.RuneAt(loc)) {
		return []byte{}
	}

	start := loc
	end := loc.Move(1, b)

	for start.X > 0 && util.IsWordChar(b.RuneAt(start.Move(-1, b))) {
		start.X--
	}

	lineLen := util.CharacterCount(b.LineBytes(loc.Y))
	for end.X < lineLen && util.IsWordChar(b.RuneAt(end)) {
		end.X++
	}

	return b.Substr(start, end)
}

// Shared returns if there are other buffers with the same file as this buffer
func (b *Buffer) Shared() bool {
	for _, buf := range OpenBuffers {
		if buf != b && buf.SharedBuffer == b.SharedBuffer {
			return true
		}
	}
	return false
}

// Modified returns if this buffer has been modified since
// being opened
func (b *Buffer) Modified() bool {
	return b.isModified
}

// Size returns the number of bytes in the current buffer
func (b *Buffer) Size() int {
	nb := 0
	for i := 0; i < b.LinesNum(); i++ {
		nb += len(b.LineBytes(i))

		if i != b.LinesNum()-1 {
			if b.Endings == FFDos {
				nb++ // carriage return
			}
			nb++ // newline
		}
	}
	return nb
}

func parseDefFromFile(f config.RuntimeFile, header *highlight.Header) *highlight.Def {
	data, err := f.Data()
	if err != nil {
		screen.TermMessage("Error loading syntax file " + f.Name() + ": " + err.Error())
		return nil
	}

	if header == nil {
		header, err = highlight.MakeHeaderYaml(data)
		if err != nil {
			screen.TermMessage("Error parsing header for syntax file " + f.Name() + ": " + err.Error())
			return nil
		}
	}

	file, err := highlight.ParseFile(data)
	if err != nil {
		screen.TermMessage("Error parsing syntax file " + f.Name() + ": " + err.Error())
		return nil
	}

	syndef, err := highlight.ParseDef(file, header)
	if err != nil {
		screen.TermMessage("Error parsing syntax file " + f.Name() + ": " + err.Error())
		return nil
	}

	return syndef
}

// findRealRuntimeSyntaxDef finds a specific syntax definition
// in the user's custom syntax files
func findRealRuntimeSyntaxDef(name string, header *highlight.Header) *highlight.Def {
	for _, f := range config.ListRealRuntimeFiles(config.RTSyntax) {
		if f.Name() == name {
			syndef := parseDefFromFile(f, header)
			if syndef != nil {
				return syndef
			}
		}
	}
	return nil
}

// findRuntimeSyntaxDef finds a specific syntax definition
// in the built-in syntax files
func findRuntimeSyntaxDef(name string, header *highlight.Header) *highlight.Def {
	for _, f := range config.ListRuntimeFiles(config.RTSyntax) {
		if f.Name() == name {
			syndef := parseDefFromFile(f, header)
			if syndef != nil {
				return syndef
			}
		}
	}
	return nil
}

func resolveIncludes(syndef *highlight.Def) {
	includes := highlight.GetIncludes(syndef)
	if len(includes) == 0 {
		return
	}

	var files []*highlight.File
	for _, f := range config.ListRuntimeFiles(config.RTSyntax) {
		data, err := f.Data()
		if err != nil {
			screen.TermMessage("Error loading syntax file " + f.Name() + ": " + err.Error())
			continue
		}

		header, err := highlight.MakeHeaderYaml(data)
		if err != nil {
			screen.TermMessage("Error parsing syntax file " + f.Name() + ": " + err.Error())
			continue
		}

		for _, i := range includes {
			if header.FileType == i {
				file, err := highlight.ParseFile(data)
				if err != nil {
					screen.TermMessage("Error parsing syntax file " + f.Name() + ": " + err.Error())
					continue
				}
				files = append(files, file)
				break
			}
		}
		if len(files) >= len(includes) {
			break
		}
	}

	highlight.ResolveIncludes(syndef, files)
}

// UpdateRules updates the syntax rules and filetype for this buffer
// This is called when the colorscheme changes
func (b *Buffer) UpdateRules() {
	if !b.Type.Syntax {
		return
	}
	ft := settingAsString(b.Settings["filetype"], "unknown")
	if ft == "off" {
		b.ClearMatches()
		b.SyntaxDef = nil
		return
	}

	b.SyntaxDef = nil

	// syntaxFileInfo is an internal helper structure
	// to store properties of one single syntax file
	type syntaxFileInfo struct {
		header    *highlight.Header
		fileName  string
		syntaxDef *highlight.Def
	}

	fnameMatches := []syntaxFileInfo{}
	headerMatches := []syntaxFileInfo{}
	syntaxFile := ""
	foundDef := false
	var header *highlight.Header
	// search for the syntax file in the user's custom syntax files
	for _, f := range config.ListRealRuntimeFiles(config.RTSyntax) {
		if f.Name() == "default" {
			continue
		}

		data, err := f.Data()
		if err != nil {
			screen.TermMessage("Error loading syntax file " + f.Name() + ": " + err.Error())
			continue
		}

		header, err = highlight.MakeHeaderYaml(data)
		if err != nil {
			screen.TermMessage("Error parsing header for syntax file " + f.Name() + ": " + err.Error())
			continue
		}

		matchedFileType := false
		matchedFileName := false
		matchedFileHeader := false

		if ft == "unknown" || ft == "" {
			if header.MatchFileName(b.Path) {
				matchedFileName = true
			}
			if len(fnameMatches) == 0 && header.MatchFileHeader(b.lines[0].data) {
				matchedFileHeader = true
			}
		} else if header.FileType == ft {
			matchedFileType = true
		}

		if matchedFileType || matchedFileName || matchedFileHeader {
			file, err := highlight.ParseFile(data)
			if err != nil {
				screen.TermMessage("Error parsing syntax file " + f.Name() + ": " + err.Error())
				continue
			}

			syndef, err := highlight.ParseDef(file, header)
			if err != nil {
				screen.TermMessage("Error parsing syntax file " + f.Name() + ": " + err.Error())
				continue
			}

			if matchedFileType {
				b.SyntaxDef = syndef
				syntaxFile = f.Name()
				foundDef = true
				break
			}

			if matchedFileName {
				fnameMatches = append(fnameMatches, syntaxFileInfo{header, f.Name(), syndef})
			} else if matchedFileHeader {
				headerMatches = append(headerMatches, syntaxFileInfo{header, f.Name(), syndef})
			}
		}
	}

	if !foundDef {
		// search for the syntax file in the built-in syntax files
		for _, f := range config.ListRuntimeFiles(config.RTSyntaxHeader) {
			data, err := f.Data()
			if err != nil {
				screen.TermMessage("Error loading syntax header file " + f.Name() + ": " + err.Error())
				continue
			}

			header, err = highlight.MakeHeader(data)
			if err != nil {
				screen.TermMessage("Error reading syntax header file", f.Name(), err)
				continue
			}

			if ft == "unknown" || ft == "" {
				if header.MatchFileName(b.Path) {
					fnameMatches = append(fnameMatches, syntaxFileInfo{header, f.Name(), nil})
				}
				if len(fnameMatches) == 0 && header.MatchFileHeader(b.lines[0].data) {
					headerMatches = append(headerMatches, syntaxFileInfo{header, f.Name(), nil})
				}
			} else if header.FileType == ft {
				syntaxFile = f.Name()
				break
			}
		}
	}

	if syntaxFile == "" {
		matches := fnameMatches
		if len(matches) == 0 {
			matches = headerMatches
		}

		length := len(matches)
		if length > 0 {
			signatureMatch := false
			if length > 1 {
				// multiple matching syntax files found, try to resolve the ambiguity
				// using signatures
				detectlimit := util.IntOpt(b.Settings["detectlimit"])
				lineCount := len(b.lines)
				limit := lineCount
				if detectlimit > 0 && lineCount > detectlimit {
					limit = detectlimit
				}

			matchLoop:
				for _, m := range matches {
					if m.header.HasFileSignature() {
						for i := 0; i < limit; i++ {
							if m.header.MatchFileSignature(b.lines[i].data) {
								syntaxFile = m.fileName
								if m.syntaxDef != nil {
									b.SyntaxDef = m.syntaxDef
									foundDef = true
								}
								header = m.header
								signatureMatch = true
								break matchLoop
							}
						}
					}
				}
			}
			if length == 1 || !signatureMatch {
				syntaxFile = matches[0].fileName
				if matches[0].syntaxDef != nil {
					b.SyntaxDef = matches[0].syntaxDef
					foundDef = true
				}
				header = matches[0].header
			}
		}
	}

	if syntaxFile != "" && !foundDef {
		// we found a syntax file using a syntax header file
		b.SyntaxDef = findRuntimeSyntaxDef(syntaxFile, header)
	}

	if b.SyntaxDef != nil {
		b.Settings["filetype"] = b.SyntaxDef.FileType
	} else {
		// search for the default file in the user's custom syntax files
		b.SyntaxDef = findRealRuntimeSyntaxDef("default", nil)
		if b.SyntaxDef == nil {
			// search for the default file in the built-in syntax files
			b.SyntaxDef = findRuntimeSyntaxDef("default", nil)
		}
	}

	if b.SyntaxDef != nil {
		resolveIncludes(b.SyntaxDef)
	}

	if b.SyntaxDef != nil {
		b.Highlighter = highlight.NewHighlighter(b.SyntaxDef)
		if b.Settings["syntax"].(bool) {
			go func() {
				b.Highlighter.HighlightStates(b)
				b.Highlighter.HighlightMatches(b, 0, b.End().Y)
				screen.Redraw()
			}()
		}
	}
}

// ClearMatches clears all of the syntax highlighting for the buffer
func (b *Buffer) ClearMatches() {
	for i := range b.lines {
		b.SetMatch(i, nil)
		b.SetState(i, nil)
	}
}

// IndentString returns this buffer's indent method (a tabstop or n spaces
// depending on the settings)
func (b *Buffer) IndentString(tabsize int) string {
	if b.Settings["tabstospaces"].(bool) {
		return util.Spaces(tabsize)
	}
	return "\t"
}

// SetCursors resets this buffer's cursors to a new list
func (b *Buffer) SetCursors(c []*Cursor) {
	b.cursors = c
	b.EventHandler.cursors = b.cursors
	b.EventHandler.active = b.curCursor
}

// AddCursor adds a new cursor to the list
func (b *Buffer) AddCursor(c *Cursor) {
	b.cursors = append(b.cursors, c)
	b.EventHandler.cursors = b.cursors
	b.EventHandler.active = b.curCursor
	b.UpdateCursors()
}

// SetCurCursor sets the current cursor
func (b *Buffer) SetCurCursor(n int) {
	b.curCursor = n
}

// GetActiveCursor returns the main cursor in this buffer
func (b *Buffer) GetActiveCursor() *Cursor {
	return b.cursors[b.curCursor]
}

// GetCursor returns the nth cursor
func (b *Buffer) GetCursor(n int) *Cursor {
	return b.cursors[n]
}

// GetCursors returns the list of cursors in this buffer
func (b *Buffer) GetCursors() []*Cursor {
	return b.cursors
}

// NumCursors returns the number of cursors
func (b *Buffer) NumCursors() int {
	return len(b.cursors)
}

// MergeCursors merges any cursors that are at the same position
// into one cursor
func (b *Buffer) MergeCursors() {
	var cursors []*Cursor
	for i := 0; i < len(b.cursors); i++ {
		c1 := b.cursors[i]
		if c1 != nil {
			for j := 0; j < len(b.cursors); j++ {
				c2 := b.cursors[j]
				if c2 != nil && i != j && c1.Loc == c2.Loc {
					b.cursors[j] = nil
				}
			}
			cursors = append(cursors, c1)
		}
	}

	b.cursors = cursors

	for i := range b.cursors {
		b.cursors[i].Num = i
	}

	if b.curCursor >= len(b.cursors) {
		b.curCursor = len(b.cursors) - 1
	}
	b.EventHandler.cursors = b.cursors
	b.EventHandler.active = b.curCursor
}

// UpdateCursors updates all the cursors indices
func (b *Buffer) UpdateCursors() {
	b.EventHandler.cursors = b.cursors
	b.EventHandler.active = b.curCursor
	for i, c := range b.cursors {
		c.Num = i
	}
}

func (b *Buffer) RemoveCursor(i int) {
	copy(b.cursors[i:], b.cursors[i+1:])
	b.cursors[len(b.cursors)-1] = nil
	b.cursors = b.cursors[:len(b.cursors)-1]
	b.curCursor = util.Clamp(b.curCursor, 0, len(b.cursors)-1)
	b.UpdateCursors()
}

// ClearCursors removes all extra cursors
func (b *Buffer) ClearCursors() {
	for i := 1; i < len(b.cursors); i++ {
		b.cursors[i] = nil
	}
	b.cursors = b.cursors[:1]
	b.UpdateCursors()
	b.curCursor = 0
	b.GetActiveCursor().Deselect(true)
}

// MoveLinesUp moves the range of lines up one row
func (b *Buffer) MoveLinesUp(start int, end int) {
	if start < 1 || start >= end || end > len(b.lines) {
		return
	}
	l := string(b.LineBytes(start - 1))
	if end == len(b.lines) {
		b.insert(
			Loc{
				util.CharacterCount(b.lines[end-1].data),
				end - 1,
			},
			[]byte{'\n'},
		)
	}
	b.Insert(
		Loc{0, end},
		l+"\n",
	)
	b.Remove(
		Loc{0, start - 1},
		Loc{0, start},
	)
}

// MoveLinesDown moves the range of lines down one row
func (b *Buffer) MoveLinesDown(start int, end int) {
	if start < 0 || start >= end || end >= len(b.lines) {
		return
	}
	l := string(b.LineBytes(end))
	b.Insert(
		Loc{0, start},
		l+"\n",
	)
	end++
	b.Remove(
		Loc{0, end},
		Loc{0, end + 1},
	)
}

var BracePairs = [][2]rune{
	{'(', ')'},
	{'{', '}'},
	{'[', ']'},
}

func (b *Buffer) findMatchingBrace(braceType [2]rune, start Loc, char rune) (Loc, bool) {
	var i int
	if char == braceType[0] {
		for y := start.Y; y < b.LinesNum(); y++ {
			l := []rune(string(b.LineBytes(y)))
			xInit := 0
			if y == start.Y {
				xInit = start.X
			}
			for x := xInit; x < len(l); x++ {
				r := l[x]
				if r == braceType[0] {
					i++
				} else if r == braceType[1] {
					i--
					if i == 0 {
						return Loc{x, y}, true
					}
				}
			}
		}
	} else if char == braceType[1] {
		for y := start.Y; y >= 0; y-- {
			l := []rune(string(b.lines[y].data))
			xInit := len(l) - 1
			if y == start.Y {
				xInit = start.X
			}
			for x := xInit; x >= 0; x-- {
				r := l[x]
				if r == braceType[1] {
					i++
				} else if r == braceType[0] {
					i--
					if i == 0 {
						return Loc{x, y}, true
					}
				}
			}
		}
	}
	return start, false
}

// If there is a brace character (for example '{' or ']') at the given start location,
// FindMatchingBrace returns the location of the matching brace for it (for example '}'
// or '['). The second returned value is true if there was no matching brace found
// for given starting location but it was found for the location one character left
// of it. The third returned value is true if the matching brace was found at all.
func (b *Buffer) FindMatchingBrace(start Loc) (Loc, bool, bool) {
	// TODO: maybe can be more efficient with utf8 package
	curLine := []rune(string(b.LineBytes(start.Y)))

	// first try to find matching brace for the given location (it has higher priority)
	if start.X >= 0 && start.X < len(curLine) {
		startChar := curLine[start.X]

		for _, bp := range BracePairs {
			if startChar == bp[0] || startChar == bp[1] {
				mb, found := b.findMatchingBrace(bp, start, startChar)
				if found {
					return mb, false, true
				}
			}
		}
	}

	if b.Settings["matchbraceleft"].(bool) {
		// failed to find matching brace for the given location, so try to find matching
		// brace for the location one character left of it
		if start.X-1 >= 0 && start.X-1 < len(curLine) {
			leftChar := curLine[start.X-1]
			left := Loc{start.X - 1, start.Y}

			for _, bp := range BracePairs {
				if leftChar == bp[0] || leftChar == bp[1] {
					mb, found := b.findMatchingBrace(bp, left, leftChar)
					if found {
						return mb, true, true
					}
				}
			}
		}
	}

	return start, false, false
}

// Retab changes all tabs to spaces or vice versa
func (b *Buffer) Retab() {
	toSpaces := b.Settings["tabstospaces"].(bool)
	tabsize := util.IntOpt(b.Settings["tabsize"])

	for i := 0; i < b.LinesNum(); i++ {
		l := b.LineBytes(i)

		ws := util.GetLeadingWhitespace(l)
		if len(ws) != 0 {
			if toSpaces {
				ws = bytes.ReplaceAll(ws, []byte{'\t'}, bytes.Repeat([]byte{' '}, tabsize))
			} else {
				ws = bytes.ReplaceAll(ws, bytes.Repeat([]byte{' '}, tabsize), []byte{'\t'})
			}
		}

		l = bytes.TrimLeft(l, " \t")

		b.Lock()
		b.lines[i].data = append(ws, l...)
		b.Unlock()

		b.MarkModified(i, i)
	}

	b.setModified()
}

// ParseCursorLocation turns a cursor location like 10:5 (LINE:COL)
// into a loc
func ParseCursorLocation(cursorPositions []string) (Loc, error) {
	startpos := Loc{0, 0}
	var err error

	// if no positions are available exit early
	if cursorPositions == nil {
		return startpos, errors.New("No cursor positions were provided.")
	}

	startpos.Y, err = strconv.Atoi(cursorPositions[0])
	startpos.Y--
	if err == nil {
		if len(cursorPositions) > 1 {
			startpos.X, err = strconv.Atoi(cursorPositions[1])
			if startpos.X > 0 {
				startpos.X--
			}
		}
	}

	return startpos, err
}

// Line returns the string representation of the given line number
func (b *Buffer) Line(i int) string {
	return string(b.LineBytes(i))
}

func (b *Buffer) Write(bytes []byte) (n int, err error) {
	b.EventHandler.InsertBytes(b.End(), bytes)
	return len(bytes), nil
}

func (b *Buffer) updateDiff(synchronous bool) {
	b.diffLock.Lock()
	defer b.diffLock.Unlock()

	b.diff = make(map[int]DiffStatus)

	if b.diffBase == nil {
		return
	}

	differ := dmp.New()

	if !synchronous {
		b.Lock()
	}
	bytes := b.Bytes()
	if !synchronous {
		b.Unlock()
	}

	baseRunes, bufferRunes, _ := differ.DiffLinesToRunes(string(b.diffBase), string(bytes))
	diffs := differ.DiffMainRunes(baseRunes, bufferRunes, false)
	lineN := 0

	for _, diff := range diffs {
		lineCount := len([]rune(diff.Text))

		switch diff.Type {
		case dmp.DiffEqual:
			lineN += lineCount
		case dmp.DiffInsert:
			var status DiffStatus
			if b.diff[lineN] == DSDeletedAbove {
				status = DSModified
			} else {
				status = DSAdded
			}
			for i := 0; i < lineCount; i++ {
				b.diff[lineN] = status
				lineN++
			}
		case dmp.DiffDelete:
			b.diff[lineN] = DSDeletedAbove
		}
	}
}

// UpdateDiff computes the diff between the diff base and the buffer content.
// The update may be performed synchronously or asynchronously.
// If an asynchronous update is already pending when UpdateDiff is called,
// UpdateDiff does not schedule another update.
func (b *Buffer) UpdateDiff() {
	if b.updateDiffTimer != nil {
		return
	}

	lineCount := b.LinesNum()
	if b.diffBaseLineCount > lineCount {
		lineCount = b.diffBaseLineCount
	}

	if lineCount < 1000 {
		b.updateDiff(true)
	} else if lineCount < 30000 {
		b.updateDiffTimer = time.AfterFunc(500*time.Millisecond, func() {
			b.updateDiffTimer = nil
			b.updateDiff(false)
			screen.Redraw()
		})
	} else {
		// Don't compute diffs for very large files
		b.diffLock.Lock()
		b.diff = make(map[int]DiffStatus)
		b.diffLock.Unlock()
	}
}

// SetDiffBase sets the text that is used as the base for diffing the buffer content
func (b *Buffer) SetDiffBase(diffBase []byte) {
	b.diffBase = diffBase
	if diffBase == nil {
		b.diffBaseLineCount = 0
	} else {
		b.diffBaseLineCount = strings.Count(string(diffBase), "\n")
	}
	b.UpdateDiff()
}

// DiffStatus returns the diff status for a line in the buffer
func (b *Buffer) DiffStatus(lineN int) DiffStatus {
	b.diffLock.RLock()
	defer b.diffLock.RUnlock()
	// Note that the zero value for DiffStatus is equal to DSUnchanged
	return b.diff[lineN]
}

// FindNextDiffLine returns the line number of the next block of diffs.
// If `startLine` is already in a block of diffs, lines in that block are skipped.
func (b *Buffer) FindNextDiffLine(startLine int, forward bool) (int, error) {
	if b.diff == nil {
		return 0, errors.New("no diff data")
	}
	startStatus, ok := b.diff[startLine]
	if !ok {
		startStatus = DSUnchanged
	}
	curLine := startLine
	for {
		curStatus, ok := b.diff[curLine]
		if !ok {
			curStatus = DSUnchanged
		}
		if curLine < 0 || curLine > b.LinesNum() {
			return 0, errors.New("no next diff hunk")
		}
		if curStatus != startStatus {
			if startStatus != DSUnchanged && curStatus == DSUnchanged {
				// Skip over the block of unchanged text
				startStatus = DSUnchanged
			} else {
				return curLine, nil
			}
		}
		if forward {
			curLine++
		} else {
			curLine--
		}
	}
}

// SearchMatch returns true if the given location is within a match of the last search.
// It is used for search highlighting
func (b *Buffer) SearchMatch(pos Loc) bool {
	return b.LineArray.SearchMatch(b, pos)
}

// WriteLog writes a string to the log buffer
func WriteLog(s string) {
	LogBuf.EventHandler.Insert(LogBuf.End(), s)
}

// GetLogBuf returns the log buffer
func GetLogBuf() *Buffer {
	return LogBuf
}