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498 lines
15 KiB
Go
498 lines
15 KiB
Go
package tview
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import (
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"math/rand"
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"regexp"
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"strconv"
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"strings"
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"unicode/utf8"
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"github.com/gdamore/tcell/v2"
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"github.com/rivo/uniseg"
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)
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// escapedTagPattern matches an escaped tag, e.g. "[red[]", at the beginning of
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// a string.
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var escapedTagPattern = regexp.MustCompile(`^\[[^\[\]]+\[+\]`)
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// stepOptions is a bit field of options for [step]. A value of 0 results in
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// [step] having the same behavior as uniseg.Step, i.e. no tview-related parsing
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// is performed.
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type stepOptions int
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// Bit fields for [stepOptions].
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const (
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stepOptionsNone stepOptions = 0
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stepOptionsStyle stepOptions = 1 << iota // Parse style tags.
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stepOptionsRegion // Parse region tags.
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)
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// stepState represents the current state of the parser implemented in [step].
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type stepState struct {
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unisegState int // The state of the uniseg parser.
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boundaries int // Information about boundaries, as returned by uniseg.Step.
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style tcell.Style // The current style.
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region string // The current region.
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escapedTagState int // States for parsing escaped tags (defined in [step]).
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grossLength int // The length of the cluster, including any tags not returned.
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// The styles for the initial call to [step].
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initialForeground tcell.Color
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initialBackground tcell.Color
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initialAttributes tcell.AttrMask
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}
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// IsWordBoundary returns true if the boundary between the returned grapheme
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// cluster and the one following it is a word boundary.
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func (s *stepState) IsWordBoundary() bool {
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return s.boundaries&uniseg.MaskWord != 0
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}
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// IsSentenceBoundary returns true if the boundary between the returned grapheme
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// cluster and the one following it is a sentence boundary.
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func (s *stepState) IsSentenceBoundary() bool {
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return s.boundaries&uniseg.MaskSentence != 0
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}
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// LineBreak returns whether the string can be broken into the next line after
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// the returned grapheme cluster. If optional is true, the line break is
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// optional. If false, the line break is mandatory, e.g. after a newline
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// character.
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func (s *stepState) LineBreak() (lineBreak, optional bool) {
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switch s.boundaries & uniseg.MaskLine {
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case uniseg.LineCanBreak:
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return true, true
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case uniseg.LineMustBreak:
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return true, false
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}
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return false, false // uniseg.LineDontBreak.
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}
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// Width returns the grapheme cluster's width in cells.
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func (s *stepState) Width() int {
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return s.boundaries >> uniseg.ShiftWidth
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}
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// GrossLength returns the grapheme cluster's length in bytes, including any
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// tags that were parsed but not explicitly returned.
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func (s *stepState) GrossLength() int {
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return s.grossLength
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}
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// Style returns the style for the grapheme cluster.
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func (s *stepState) Style() tcell.Style {
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return s.style
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}
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// step uses uniseg.Step to iterate over the grapheme clusters of a string but
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// (optionally) also parses the string for style or region tags.
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//
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// This function can be called consecutively to extract all grapheme clusters
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// from str, without returning any contained (parsed) tags. The return values
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// are the first grapheme cluster, the remaining string, and the new state. Pass
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// the remaining string and the returned state to the next call. If the rest
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// string is empty, parsing is complete. Call the returned state's methods for
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// boundary and width information.
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//
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// The returned cluster may be empty if the given string consists of only
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// (parsed) tags. The boundary and width information will be meaningless in
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// this case but the style will describe the style at the end of the string.
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//
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// Pass nil for state on the first call. This will assume an initial style with
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// [Styles.PrimitiveBackgroundColor] as the background color and
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// [Styles.PrimaryTextColor] as the text color, no current region. If you want
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// to start with a different style or region, you can set the state accordingly
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// but you must then set [state.unisegState] to -1.
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//
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// You may call uniseg.HasTrailingLineBreakInString on the last non-empty
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// cluster to determine if the string ends with a hard line break.
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func step(str string, state *stepState, opts stepOptions) (cluster, rest string, newState *stepState) {
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// Set up initial state.
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if state == nil {
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state = &stepState{
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unisegState: -1,
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style: tcell.StyleDefault.Background(Styles.PrimitiveBackgroundColor).Foreground(Styles.PrimaryTextColor),
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}
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}
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if state.unisegState < 0 {
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state.initialForeground, state.initialBackground, state.initialAttributes = state.style.Decompose()
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}
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if len(str) == 0 {
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newState = state
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return
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}
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// Get a grapheme cluster.
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preState := state.unisegState
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cluster, rest, state.boundaries, state.unisegState = uniseg.StepString(str, preState)
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state.grossLength = len(cluster)
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// Parse tags.
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if opts != 0 {
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const (
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etNone int = iota
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etStart
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etChar
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etClosing
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)
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// Finite state machine for escaped tags.
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switch state.escapedTagState {
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case etStart:
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if cluster[0] == '[' || cluster[0] == ']' { // Invalid escaped tag.
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state.escapedTagState = etNone
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} else { // Other characters are allowed.
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state.escapedTagState = etChar
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}
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case etChar:
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if cluster[0] == ']' { // In theory, this should not happen.
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state.escapedTagState = etNone
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} else if cluster[0] == '[' { // Starting closing sequence.
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// Swallow the first one.
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cluster, rest, state.boundaries, state.unisegState = uniseg.StepString(rest, preState)
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state.grossLength = len(cluster)
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if cluster[0] == ']' {
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state.escapedTagState = etNone
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} else {
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state.escapedTagState = etClosing
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}
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} // More characters. Remain in etChar.
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case etClosing:
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if cluster[0] != '[' {
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state.escapedTagState = etNone
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}
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}
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// Regular tags.
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if state.escapedTagState == etNone {
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if cluster[0] == '[' {
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// We've already opened a tag. Parse it.
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length, style, region := parseTag(str, state)
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if length > 0 {
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state.style = style
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state.region = region
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cluster, rest, state.boundaries, state.unisegState = uniseg.StepString(str[length:], preState)
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state.grossLength = len(cluster) + length
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}
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// Is this an escaped tag?
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if escapedTagPattern.MatchString(str[length:]) {
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state.escapedTagState = etStart
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}
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}
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if len(rest) > 0 && rest[0] == '[' {
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// A tag might follow the cluster. If so, we need to fix the state
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// for the boundaries to be correct.
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if length, _, _ := parseTag(rest, state); length > 0 {
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if len(rest) > length {
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_, l := utf8.DecodeRuneInString(rest[length:])
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cluster += rest[length : length+l]
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}
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cluster, _, state.boundaries, state.unisegState = uniseg.StepString(cluster, preState)
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}
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}
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}
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}
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newState = state
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return
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}
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// parseTag parses str for consecutive style and/or region tags, assuming that
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// str starts with the opening bracket for the first tag. It returns the string
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// length of all valid tags (0 if the first tag is not valid) and the updated
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// style and region for valid tags (based on the provided state).
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func parseTag(str string, state *stepState) (length int, style tcell.Style, region string) {
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// Automata states for parsing tags.
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const (
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tagStateNone = iota
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tagStateDoneTag
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tagStateStart
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tagStateRegionStart
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tagStateEndForeground
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tagStateStartBackground
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tagStateNumericForeground
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tagStateNameForeground
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tagStateEndBackground
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tagStateStartAttributes
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tagStateNumericBackground
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tagStateNameBackground
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tagStateAttributes
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tagStateRegionEnd
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tagStateRegionName
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tagStateEndAttributes
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tagStateStartURL
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tagStateEndURL
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tagStateURL
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)
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// Helper function which checks if the given byte is one of a list of
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// characters, including letters and digits.
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isOneOf := func(b byte, chars string) bool {
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if b >= 'a' && b <= 'z' || b >= 'A' && b <= 'Z' || b >= '0' && b <= '9' {
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return true
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}
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return strings.IndexByte(chars, b) >= 0
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}
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// Attribute map.
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attrs := map[byte]tcell.AttrMask{
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'B': tcell.AttrBold,
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'U': tcell.AttrUnderline,
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'I': tcell.AttrItalic,
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'L': tcell.AttrBlink,
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'D': tcell.AttrDim,
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'S': tcell.AttrStrikeThrough,
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'R': tcell.AttrReverse,
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}
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var (
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tagState, tagLength int
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tempStr strings.Builder
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)
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tStyle := state.style
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tRegion := state.region
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// Process state transitions.
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for len(str) > 0 {
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ch := str[0]
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str = str[1:]
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tagLength++
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// Transition.
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switch tagState {
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case tagStateNone:
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if ch == '[' { // Start of a tag.
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tagState = tagStateStart
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} else { // Not a tag. We're done.
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return
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}
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case tagStateStart:
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if ch == '"' { // Start of a region tag.
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tempStr.Reset()
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tagState = tagStateRegionStart
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} else if !isOneOf(ch, "#:-") { // Invalid style tag.
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return
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} else if ch == '-' { // Reset foreground color.
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tStyle = tStyle.Foreground(state.initialForeground)
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tagState = tagStateEndForeground
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} else if ch == ':' { // No foreground color.
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tagState = tagStateStartBackground
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} else {
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tempStr.Reset()
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tempStr.WriteByte(ch)
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if ch == '#' { // Numeric foreground color.
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tagState = tagStateNumericForeground
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} else { // Letters or numbers.
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tagState = tagStateNameForeground
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}
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}
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case tagStateEndForeground:
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if ch == ']' { // End of tag.
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tagState = tagStateDoneTag
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} else if ch == ':' {
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tagState = tagStateStartBackground
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} else { // Invalid tag.
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return
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}
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case tagStateNumericForeground:
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if ch == ']' || ch == ':' {
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if tempStr.Len() != 7 { // Must be #rrggbb.
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return
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}
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tStyle = tStyle.Foreground(tcell.GetColor(tempStr.String()))
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}
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if ch == ']' { // End of tag.
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tagState = tagStateDoneTag
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} else if ch == ':' { // Start of background color.
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tagState = tagStateStartBackground
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} else if strings.IndexByte("0123456789abcdefABCDEF", ch) >= 0 { // Hex digit.
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tempStr.WriteByte(ch)
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tagState = tagStateNumericForeground
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} else { // Invalid tag.
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return
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}
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case tagStateNameForeground:
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if ch == ']' || ch == ':' {
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name := tempStr.String()
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if name[0] >= '0' && name[0] <= '9' { // Must not start with a digit.
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return
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}
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tStyle = tStyle.Foreground(tcell.ColorNames[name])
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}
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if !isOneOf(ch, "]:") { // Invalid tag.
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return
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} else if ch == ']' { // End of tag.
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tagState = tagStateDoneTag
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} else if ch == ':' { // Start of background color.
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tagState = tagStateStartBackground
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} else { // Letters or numbers.
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tempStr.WriteByte(ch)
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}
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case tagStateStartBackground:
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if !isOneOf(ch, "#:-]") { // Invalid style tag.
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return
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} else if ch == ']' { // End of tag.
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tagState = tagStateDoneTag
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} else if ch == '-' { // Reset background color.
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tStyle = tStyle.Background(state.initialBackground)
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tagState = tagStateEndBackground
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} else if ch == ':' { // No background color.
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tagState = tagStateStartAttributes
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} else {
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tempStr.Reset()
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tempStr.WriteByte(ch)
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if ch == '#' { // Numeric background color.
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tagState = tagStateNumericBackground
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} else { // Letters or numbers.
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tagState = tagStateNameBackground
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}
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}
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case tagStateEndBackground:
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if ch == ']' { // End of tag.
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tagState = tagStateDoneTag
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} else if ch == ':' { // Start of attributes.
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tagState = tagStateStartAttributes
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} else { // Invalid tag.
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return
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}
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case tagStateNumericBackground:
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if ch == ']' || ch == ':' {
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if tempStr.Len() != 7 { // Must be #rrggbb.
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return
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}
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tStyle = tStyle.Background(tcell.GetColor(tempStr.String()))
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}
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if ch == ']' { // End of tag.
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tagState = tagStateDoneTag
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} else if ch == ':' { // Start of attributes.
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tagState = tagStateStartAttributes
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} else if strings.IndexByte("0123456789abcdefABCDEF", ch) >= 0 { // Hex digit.
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tempStr.WriteByte(ch)
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tagState = tagStateNumericBackground
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} else { // Invalid tag.
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return
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}
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case tagStateNameBackground:
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if ch == ']' || ch == ':' {
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name := tempStr.String()
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if name[0] >= '0' && name[0] <= '9' { // Must not start with a digit.
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return
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}
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tStyle = tStyle.Background(tcell.ColorNames[name])
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}
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if !isOneOf(ch, "]:") { // Invalid tag.
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return
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} else if ch == ']' { // End of tag.
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tagState = tagStateDoneTag
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} else if ch == ':' { // Start of background color.
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tagState = tagStateStartAttributes
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} else { // Letters or numbers.
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tempStr.WriteByte(ch)
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}
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case tagStateStartAttributes:
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if ch == ']' { // End of tag.
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tagState = tagStateDoneTag
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} else if ch == '-' { // Reset attributes.
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tStyle = tStyle.Attributes(state.initialAttributes)
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tagState = tagStateEndAttributes
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} else if ch == ':' { // Start of URL.
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tagState = tagStateStartURL
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} else if strings.IndexByte("buildsrBUILDSR", ch) >= 0 { // Attribute tag.
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tempStr.Reset()
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tempStr.WriteByte(ch)
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tagState = tagStateAttributes
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} else { // Invalid tag.
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return
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}
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case tagStateAttributes:
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if ch == ']' || ch == ':' {
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flags := tempStr.String()
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_, _, a := tStyle.Decompose()
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for index := 0; index < len(flags); index++ {
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ch := flags[index]
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if ch >= 'a' && ch <= 'z' {
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a |= attrs[ch-('a'-'A')]
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} else {
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a &^= attrs[ch]
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}
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}
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tStyle = tStyle.Attributes(a)
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}
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if ch == ']' { // End of tag.
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tagState = tagStateDoneTag
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} else if ch == ':' { // Start of URL.
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tagState = tagStateStartURL
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} else if strings.IndexByte("buildsrBUILDSR", ch) >= 0 { // Attribute tag.
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tempStr.WriteByte(ch)
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} else { // Invalid tag.
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return
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}
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case tagStateEndAttributes:
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if ch == ']' { // End of tag.
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tagState = tagStateDoneTag
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} else if ch == ':' { // Start of URL.
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tagState = tagStateStartURL
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} else { // Invalid tag.
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return
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}
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case tagStateStartURL:
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if ch == ']' { // End of tag.
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tagState = tagStateDoneTag
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} else if ch == '-' { // Reset URL.
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tStyle = tStyle.Url("").UrlId("")
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tagState = tagStateEndURL
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} else { // URL character.
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tempStr.Reset()
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tempStr.WriteByte(ch)
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tStyle = tStyle.UrlId(strconv.Itoa(int(rand.Uint32()))) // Generate a unique ID for this URL.
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tagState = tagStateURL
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}
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case tagStateEndURL:
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if ch == ']' { // End of tag.
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tagState = tagStateDoneTag
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} else { // Invalid tag.
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return
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}
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case tagStateURL:
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if ch == ']' { // End of tag.
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tStyle = tStyle.Url(tempStr.String())
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tagState = tagStateDoneTag
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} else { // URL character.
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tempStr.WriteByte(ch)
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}
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case tagStateRegionStart:
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if ch == '"' { // End of region tag.
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tagState = tagStateRegionEnd
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} else if isOneOf(ch, "_,;: -.") { // Region name.
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tempStr.WriteByte(ch)
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tagState = tagStateRegionName
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} else { // Invalid tag.
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return
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}
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case tagStateRegionEnd:
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if ch == ']' { // End of tag.
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tRegion = tempStr.String()
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tagState = tagStateDoneTag
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} else { // Invalid tag.
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return
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}
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case tagStateRegionName:
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if ch == '"' { // End of region tag.
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tagState = tagStateRegionEnd
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} else if isOneOf(ch, "_,;: -.") { // Region name.
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tempStr.WriteByte(ch)
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} else { // Invalid tag.
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return
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}
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}
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// The last transition led to a tag end. Make the tag permanent.
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if tagState == tagStateDoneTag {
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length, style, region = tagLength, tStyle, tRegion
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tagState = tagStateNone // Reset state.
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}
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}
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return
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}
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