chronos/src/parser.typ

#import "diagram.typ": diagram, _par, _evt, _gap
#import "participant.typ": SHAPES
#import "separator.typ": _sep, _delay
#import "sequence.typ": _seq, _ret
#import "group.typ": _grp, _alt
#import "note.typ": _note, SIDES

#let COLORS = (
  aliceblue: rgb("#f0f8ff"),
  antiquewhite: rgb("#faebd7"),
  aqua: rgb("#00ffff"),
  aquamarine: rgb("#7fffd4"),
  azure: rgb("#f0ffff"),
  beige: rgb("#f5f5dc"),
  bisque: rgb("#ffe4c4"),
  black: rgb("#000000"),
  blanchedalmond: rgb("#ffebcd"),
  blue: rgb("#0000ff"),
  blueviolet: rgb("#8a2be2"),
  brown: rgb("#a52a2a"),
  burlywood: rgb("#deb887"),
  cadetblue: rgb("#5f9ea0"),
  chartreuse: rgb("#7fff00"),
  chocolate: rgb("#d2691e"),
  coral: rgb("#ff7f50"),
  cornflowerblue: rgb("#6495ed"),
  cornsilk: rgb("#fff8dc"),
  crimson: rgb("#dc143c"),
  cyan: rgb("#00ffff"),
  darkblue: rgb("#00008b"),
  darkcyan: rgb("#008b8b"),
  darkgoldenrod: rgb("#b8860b"),
  darkgray: rgb("#a9a9a9"),
  darkgreen: rgb("#006400"),
  darkgrey: rgb("#a9a9a9"),
  darkkhaki: rgb("#bdb76b"),
  darkmagenta: rgb("#8b008b"),
  darkolivegreen: rgb("#556b2f"),
  darkorange: rgb("#ff8c00"),
  darkorchid: rgb("#9932cc"),
  darkred: rgb("#8b0000"),
  darksalmon: rgb("#e9967a"),
  darkseagreen: rgb("#8fbc8f"),
  darkslateblue: rgb("#483d8b"),
  darkslategray: rgb("#2f4f4f"),
  darkslategrey: rgb("#2f4f4f"),
  darkturquoise: rgb("#00ced1"),
  darkviolet: rgb("#9400d3"),
  deeppink: rgb("#ff1493"),
  deepskyblue: rgb("#00bfff"),
  dimgray: rgb("#696969"),
  dimgrey: rgb("#696969"),
  dodgerblue: rgb("#1e90ff"),
  firebrick: rgb("#b22222"),
  floralwhite: rgb("#fffaf0"),
  forestgreen: rgb("#228b22"),
  fuchsia: rgb("#ff00ff"),
  gainsboro: rgb("#dcdcdc"),
  ghostwhite: rgb("#f8f8ff"),
  gold: rgb("#ffd700"),
  goldenrod: rgb("#daa520"),
  gray: rgb("#808080"),
  green: rgb("#008000"),
  greenyellow: rgb("#adff2f"),
  grey: rgb("#808080"),
  honeydew: rgb("#f0fff0"),
  hotpink: rgb("#ff69b4"),
  indianred: rgb("#cd5c5c"),
  indigo: rgb("#4b0082"),
  ivory: rgb("#fffff0"),
  khaki: rgb("#f0e68c"),
  lavender: rgb("#e6e6fa"),
  lavenderblush: rgb("#fff0f5"),
  lawngreen: rgb("#7cfc00"),
  lemonchiffon: rgb("#fffacd"),
  lightblue: rgb("#add8e6"),
  lightcoral: rgb("#f08080"),
  lightcyan: rgb("#e0ffff"),
  lightgoldenrodyellow: rgb("#fafad2"),
  lightgray: rgb("#d3d3d3"),
  lightgreen: rgb("#90ee90"),
  lightgrey: rgb("#d3d3d3"),
  lightpink: rgb("#ffb6c1"),
  lightsalmon: rgb("#ffa07a"),
  lightseagreen: rgb("#20b2aa"),
  lightskyblue: rgb("#87cefa"),
  lightslategray: rgb("#778899"),
  lightslategrey: rgb("#778899"),
  lightsteelblue: rgb("#b0c4de"),
  lightyellow: rgb("#ffffe0"),
  lime: rgb("#00ff00"),
  limegreen: rgb("#32cd32"),
  linen: rgb("#faf0e6"),
  magenta: rgb("#ff00ff"),
  maroon: rgb("#800000"),
  mediumaquamarine: rgb("#66cdaa"),
  mediumblue: rgb("#0000cd"),
  mediumorchid: rgb("#ba55d3"),
  mediumpurple: rgb("#9370db"),
  mediumseagreen: rgb("#3cb371"),
  mediumslateblue: rgb("#7b68ee"),
  mediumspringgreen: rgb("#00fa9a"),
  mediumturquoise: rgb("#48d1cc"),
  mediumvioletred: rgb("#c71585"),
  midnightblue: rgb("#191970"),
  mintcream: rgb("#f5fffa"),
  mistyrose: rgb("#ffe4e1"),
  moccasin: rgb("#ffe4b5"),
  navajowhite: rgb("#ffdead"),
  navy: rgb("#000080"),
  oldlace: rgb("#fdf5e6"),
  olive: rgb("#808000"),
  olivedrab: rgb("#6b8e23"),
  orange: rgb("#ffa500"),
  orangered: rgb("#ff4500"),
  orchid: rgb("#da70d6"),
  palegoldenrod: rgb("#eee8aa"),
  palegreen: rgb("#98fb98"),
  paleturquoise: rgb("#afeeee"),
  palevioletred: rgb("#db7093"),
  papayawhip: rgb("#ffefd5"),
  peachpuff: rgb("#ffdab9"),
  peru: rgb("#cd853f"),
  pink: rgb("#ffc0cb"),
  plum: rgb("#dda0dd"),
  powderblue: rgb("#b0e0e6"),
  purple: rgb("#800080"),
  rebeccapurple: rgb("#663399"),
  red: rgb("#ff0000"),
  rosybrown: rgb("#bc8f8f"),
  royalblue: rgb("#4169e1"),
  saddlebrown: rgb("#8b4513"),
  salmon: rgb("#fa8072"),
  sandybrown: rgb("#f4a460"),
  seagreen: rgb("#2e8b57"),
  seashell: rgb("#fff5ee"),
  sienna: rgb("#a0522d"),
  silver: rgb("#c0c0c0"),
  skyblue: rgb("#87ceeb"),
  slateblue: rgb("#6a5acd"),
  slategray: rgb("#708090"),
  slategrey: rgb("#708090"),
  snow: rgb("#fffafa"),
  springgreen: rgb("#00ff7f"),
  steelblue: rgb("#4682b4"),
  tan: rgb("#d2b48c"),
  teal: rgb("#008080"),
  thistle: rgb("#d8bfd8"),
  tomato: rgb("#ff6347"),
  turquoise: rgb("#40e0d0"),
  violet: rgb("#ee82ee"),
  wheat: rgb("#f5deb3"),
  white: rgb("#ffffff"),
  whitesmoke: rgb("#f5f5f5"),
  yellow: rgb("#ffff00"),
  yellowgreen: rgb("#9acd32"),
)

#let CREOLE = (
  "bold": (
    open: "**",
    close: "**",
    func: strong
  ),
  "italic": (
    open: "//",
    close: "//",
    func: emph
  ),
  "mono": (
    open: "\"\"",
    close: "\"\"",
    func: it => text(it, font: "DejaVu Sans Mono")
  ),
  "stricken": (
    open: "--",
    close: "--",
    func: strike
  ),
  "under": (
    open: "__",
    close: "__",
    func: underline
  ),
  "wavy": (
    open: "~~",
    close: "~~",
    func: it => panic("Wavy underline is not supported (see https://github.com/typst/typst/issues/2835)")
  )
)

#let parse-creole(txt) = {
  txt = txt.replace("\\n", "\n")
           .replace("<<", sym.quote.angle.double.l)
           .replace(">>", sym.quote.angle.double.r)

  let part-stack = ()
  let style-stack = ()
  let cur-style = none

  let steps = ()
  let tmp = ""
  for char in txt {
    cur-style = if style-stack.len() == 0 {
      none
    } else {
      style-stack.last()
    }

    tmp += char

    for (name, style) in CREOLE.pairs() {
      if tmp.ends-with(style.close) {
        //if cur-style == name {
        if name in style-stack {
          tmp = tmp.slice(0, tmp.len() - style.close.len())

          let to-append = ""
          let rev-style-stack = style-stack.rev()
          let i = rev-style-stack.position(s => s == name)
          for _ in range(i) {
            let style = style-stack.pop()
            tmp = CREOLE.at(style).open + tmp
          }
          style-stack.pop()

          if tmp.len() == 0 {
            if part-stack.len() != 0 {
              to-append += (style.func)(part-stack.pop())
            }
          } else {
            to-append += (style.func)(tmp)
          }
          tmp = ""
          part-stack.last() = part-stack.last() + to-append

          break
        }
      }
      if tmp.ends-with(style.open) {
        tmp = tmp.slice(0, tmp.len() - style.open.len())
        part-stack.push(tmp)
        tmp = ""
        style-stack.push(name)
        break
      }
    }
    steps.push((part-stack, tmp, style-stack))
  }
  if part-stack.len() == 0 {
    part-stack.push(tmp)
  } else {
    part-stack.last() += tmp
  }

  if style-stack.len() != 0 {
    let dbg-steps = steps
    let dbg-txt = txt
    panic("Unclosed '" + style-stack.last() + "' style in string '" + txt + "'")
  }

  return part-stack.join()
}

#let parse-color(value) = {
  if value.starts-with("#") {
    value = value.slice(1)
  }
  let m = value.match(regex("^(.+)([|/\\\-])(.+)$"))
  if m != none {
    let (col1, angle, col2) = m.captures
    col1 = parse-color(col1)
    col2 = parse-color(col2)
    angle = (
      "|": 0deg,
      "/": 45deg,
      "-": 90deg,
      "\\": 135deg
    ).at(angle)
    return gradient.linear(col1, col2, angle: angle)
  }
  
  if lower(value) in COLORS {
    return COLORS.at(lower(value))
  }

  return rgb(value)
}

#let is-boundary-stmt(line) = {
  return line.starts-with("@startuml") or line.starts-with("@enduml")
}

#let is-comment-stmt(line) = {
  return line.starts-with("'")
}

#let is-ret-stmt(line) = {
  return line.starts-with("return")
}

#let parse-ret-stmt(line) = {
  let m = line.match(regex("^return(\s+(.*?))?$"))
  let comment = m.captures.last()
  return _ret(comment: comment)
}

#let is-par-stmt(line) = {
  for shape in SHAPES {
    if shape == "custom" {
      continue
    }
    if line.starts-with(shape) {
      return true
    }
  }
  return false
}

#let parse-par-stmt(line) = {
  let arg-stack = line.split(" ")
  let arg-stack2 = ()
  let in-string = false
  for arg in arg-stack {
    if in-string {
      if arg.ends-with("\"") {
        arg = arg.slice(0, arg.len()-1)
        in-string = false
      }
      arg-stack2.last() += " " + arg
    } else {
      if arg.starts-with("\"") {
        arg = arg.slice(1)
        if arg.ends-with("\"") {
          arg = arg.slice(0, arg.len()-1)
        } else {
          in-string = true
        }
      }
      if not in-string and arg.trim().len() == 0 {
        continue
      }
      arg-stack2.push(arg)
    }
  }
  arg-stack = arg-stack2.rev()

  let shape = arg-stack.pop()
  let display-name = auto
  let name = arg-stack.pop()
  let color = auto
  
  while arg-stack.len() != 0 {
    let arg = arg-stack.pop()
    if arg == "as" {
      display-name = name
      name = arg-stack.pop()
    } else if arg.starts-with("#") {
      color = parse-color(arg)
    }
  }

  if display-name != auto {
    display-name = parse-creole(display-name)
  }

  return _par(
    name,
    display-name: display-name,
    shape: shape,
    color: color
  )
}

#let is-gap-stmt(line) = {
  return line == "|||" or line.match(regex("\|\|\d+\|\|")) != none
}

#let parse-gap-stmt(line) = {
  if line == "|||" {
    return _gap()
  }
  let size = int(line.slice(2, line.len() - 2))
  return _gap(size: size)
}

#let is-delay-stmt(line) = {
  return line.starts-with("...")
}

#let parse-delay-stmt(line) = {
  if line == "..." {
    return _delay()
  }
  let m = line.match(regex("\.\.\.\s*(.*?)\s*\.\.\."))
  let name = m.captures.first()
  return _delay(name: name)
}

#let is-sep-stmt(line) = {
  return line.starts-with("==") and line.ends-with("==")
}

#let parse-sep-stmt(line) = {
  let name = line.slice(2, -2).trim()
  return _sep(name)
}

#let is-evt-stmt(line) = {
  return (
    line.starts-with("activate") or
    line.starts-with("deactivate") or
    line.starts-with("create") or
    line.starts-with("destroy")
  )
}

#let parse-evt-stmt(line) = {
  let (evt, par, col) = line.match(
    regex(```(?x)
      ^
      (?<evt>.+?)
      \s+
      (?<par>.+?)
      (?<col>\s+.*)?
      $```.text
    )
  ).captures
  if col != none {
    col = parse-color(col.trim())
  }

  // TODO: lifeline style (i.e. use col)

  let event = (
    "activate": "enable",
    "deactivate": "disable",
    "create": "create",
    "destroy": "destroy"
  ).at(evt)
  return _evt(par, event)
}

#let is-grp-stmt(line) = {
  return (
    line.starts-with("group") or
    line.starts-with("loop") or
    line.starts-with("alt") or
    line.starts-with("else")
  )
}

#let parse-grp-stmt(line) = {
  let words = line.split(" ")
  let group-type = words.first()
  let rest = words.slice(1).join(" ")
  let is-group = group-type == "group"
  let name = group-type
  let desc = rest
  if is-group {
    let m = rest.match(
      regex(
        ```(?x)
        ^
        (.*?)
        (\[.*\])?
        $
        ```.text
      )
    )
    name = m.captures.first()
    desc = m.captures.last()
    if desc != none {
      desc = desc.trim(regex("[\[\]]*"))
    }
  }
  return (
    name: name,
    desc: desc,
    type: if is-group {
      "default"
    } else {
      group-type
    }
  )
}

#let is-simple-note-stmt(line) = {
  return line.starts-with(regex("/?\s*[hr]?note")) and line.contains(":")
}

#let parse-note-data(stmt) = {
  let aligned = stmt.starts-with("/")
  stmt = stmt.trim(regex("/?\s*"))
  let data-parts = stmt.split(regex("\s+"))
  let note-type = data-parts.at(0)
  let shape = (
    "note": "default",
    "hnote": "hex",
    "rnote": "rect"
  ).at(note-type)
  let side = data-parts.at(1)
  if side not in SIDES {
    panic("Invalid note side '" + side + "'")
  }

  let color = auto
  if data-parts.last().starts-with("#") {
    color = parse-color(data-parts.pop())
  }

  let pos = none
  if side == "left" or side == "right" {
    if data-parts.len() >= 3 {
      if data-parts.at(2) == "of" and data-parts.len() >= 4 {
        pos = data-parts.at(3)
      } else {
        pos = data-parts.at(2)
      }
    }
  } else if side == "over" {
    pos = data-parts.slice(2)
                    .join(" ")
                    .split(",")
                    .map(p => p.trim())
    if pos.len() == 1 {
      pos = pos.first()
    }
  }

  return (
    side: side,
    shape: shape,
    color: color,
    pos: pos,
    aligned: aligned
  )
}
#let parse-simple-note-stmt(line) = {
  let (data, ..note) = line.split(":")
  note = note.join(":")
  note = parse-creole(note.trim())

  let note-data = parse-note-data(data)

  return _note(
    note-data.side,
    note,
    color: note-data.color,
    pos: note-data.pos,
    shape: note-data.shape,
    aligned: note-data.aligned
  )
}

#let is-multiline-note-stmt(line) = {
  return line.starts-with(regex("/?\s*[hr]?note")) and not line.contains(":")
}

#let parse-multiline-note-stmt(line) = {
  let note-data = parse-note-data(line)
  note-data.insert("lines", ())

  return note-data
}

#let parse-seq-tips(arrow) = {
  let m = arrow.trim().match(
    regex(```(?x)
      ^
      ([ox])?
      (<|<<|\\|\\\\|/|//)?
      (-{1,2})
      (>|>>|\\|\\\\|/|//)?
      ([ox])?
      $
    ```.text
    )
  )

  if m == none {
    //panic(arrow)
    return none
  }

  let flip = false
  let (pre-start, start, mid, end, post-end) = m.captures
  if start != none and end == none {
    flip = true
  }

  if start != none {
    start = (
      "<": ">",
      "\\": "/",
      "\\\\": "//",
      "/": "\\",
      "//": "\\\\",
    ).at(start, default: start)
  }

  let start-tip = (pre-start, start).filter(t => t != none)
  let end-tip = (post-end, end).filter(t => t != none)
  if start-tip.len() == 1 {
    start-tip = start-tip.first()
  } else if start-tip.len() == 0 {
    start-tip = ""
  }
  if end-tip.len() == 1 {
    end-tip = end-tip.first()
  } else if end-tip.len() == 0 {
    end-tip = ""
  }

  if pre-start == "x" {
    start-tip = "x"
  }
  if post-end == "x" {
    end-tip = "x"
  }

  return (start-tip, mid == "--", end-tip, flip)
}

#let parse-seq-stmt(line) = {
  let p1 = ""
  let arrow = ""
  let p2 = ""
  let mods = ""
  let comment = ""
  let color = ""
  let state = "idle"
  let in-string = false
  let steps = ()
  let post-par = ""
  let p1-as = ""
  let p2-as = ""

  for char in line.clusters() {
    steps.push((state, char, in-string))
    if steps.len() > 12 {
      let a = steps
    }

    // Idle: go until first non whitespace character
    // if first char is " -> in-string
    if state == "idle" {
      if char.match(regex("\s")) == none {
        if char == "\"" {
          in-string = true
        } else {
          p1 += char
        }

        if p1 in ("[", "?") {
          state = "post-p1"
        } else {
          state = "p1"
        }
      }
    
    // First participant: if in string, go until end of string,
    // otherwise go until arrow character
    } else if state == "p1" {
      if in-string {
        if char == "\"" {
          in-string = false
          state = "post-p1"
        } else {
          p1 += char
        }
      } else {
        if char.match(regex(`-|<|>|\\|\\\\|/|//`.text)) != none {
          arrow += char
          state = "arrow"
        } else if char.match(regex("\s")) != none {
          state = "post-p1"
        } else {
          p1 += char
          if p1 in ("[", "?") {
            state = "post-p1"
          }
        }
      }

    } else if state == "post-p1" {
      if char.match(regex(`o|x|-|<|>|\\|\\\\|/|//`.text)) != none {
        arrow += char
        state = "arrow"

      } else if char.match(regex("\s")) == none {
        post-par += char
        if post-par.match(regex("as\s")) != none {
          state = "p1-as"
          post-par = ""
        
        } else if post-par.match("^(a(s(\s?))?)?$") == none {
          panic("Unexpected characters '" + post-par + "' after first participant")
        }
      }

    } else if state == "p1-as" {
      if char.match(regex("\s|o|x|-|<|>|\\|\\\\|/|//")) != none {
        arrow += char
        state = "arrow"
      } else {
        p1-as += char
      }
    
    // Arrow: 
    } else if state == "arrow" {
      if char.match(regex(`o|x|-|<|>|\\|\\\\|/|//`.text)) != none {
        arrow += char
      } else {
        if char == "\"" {
          in-string = true
          state = "p2"
        } else if char == " " {
          state = "pre-p2"
        } else {
          p2 += char
          state = "p2"
        }
      }
    
    } else if state == "pre-p2" {
      if char.match(regex("\s")) == none {
        if char == "\"" {
          in-string = true
        } else {
          p2 += char
        }
        state = "p2"
      }
    
    
    // Second participant: if in string go until end of string
    } else if state == "p2" {
      if in-string {
        if char == "\"" {
          in-string = false
          state = "post-p2"
        } else {
          p2 += char
        }
      } else {
        if char.match(regex("\s")) != none {
          state = "post-p2"
        } else if char in "+-*!" {
          state = "mods"
          mods += char
        } else if char == ":" {
          state = "comment"
        } else {
          p2 += char
        }
      }
    
    } else if state == "post-p2" {
      if post-par.len() == 0 {
        if char.match(regex("\s")) != none {
          continue
        }
        if char in "+-*!" {
          state = "mods"
          mods += char
        } else if char == ":" {
          state = "comment"
        } else {
          post-par += char
        }
      
      } else {
        post-par += char
        if post-par.match(regex("^\s*as\s$")) != none {
          state = "p2-as"
          post-par = ""
        
        } else if post-par.match(regex("^\s*(a(s(\s?))?)?$")) == none {
          let a = steps
          panic("Unexpected characters '" + post-par + "' after second participant")
        }
      }

    } else if state == "p2-as" {
      if char.match(regex("\s|\+|-|\*|!")) != none {
        mods += char
        state = "mods"
      } else if char == ":" {
        state = "comment"
      } else {
        p2-as += char
      }
    
    } else if state == "mods" {
      if char.match(regex("\s|\+|-|\*|!")) != none {
        mods += char
      } else {
        if char == ":" {
          state = "comment"
        } else if char.match(regex("\s")) != none {
          state = "post-mods"
        } else {
          panic("Unexpected character '" + char + "' after mods")
        }
      }

    } else if state == "post-mods" {
      if char == ":" {
        state = "comment"
      }

    } else if state == "comment" {
      comment += char
    }
  }
  p1 = parse-creole(p1)
  p2 = parse-creole(p2)
  comment = parse-creole(comment.trim())
  p1-as = p1-as.trim()
  p2-as = p2-as.trim()
  let elmts = ()

  if p1-as != "" {
    elmts += _par(p1-as, display-name: p1)
    p1 = p1-as
  }
  if p2-as != "" {
    elmts += _par(p2-as, display-name: p2)
    p2 = p2-as
  }

  /*let m = line.match(
    regex(```(?x)
      ^
      (?<p1>[a-zA-Z0-9_]+)
      \s*
      (?<arrow>[^o].*?)
      \s*
      (?<p2>[a-zA-Z0-9_]+)
      \s*
      (?<mods>[+\-*! ]{2,})?
      \s*
      (:\s*(?<comment>.*))?
      ```.text
    )
  )*/

  /*
  let m = line.match(
    regex(```(?x)
      ^
      (?<p1>[a-zA-Z0-9_\[?]+)
      \s*
      (?<arrow>[^o].*?)
      \s*
      (?<p2>[a-zA-Z0-9_\]?]+)
      \s*
      (?<mods>[+\-*! ]*?)
      \s*
      (?<color>\#.+)?
      \s*
      (?::\s*(?<comment>.*))?
      $
      ```.text
    )
  )

  if m == none {
    panic(line)
  }
  let (p1, arrow, p2, mods, color, comment) = m.captures
  */

  /*
  let p1 = line.find(regex("^[a-zA-Z0-9_]+"))
  
  line = line.slice(p1.len()).trim()
  let i = line.position(regex("(?:[^o])[a-zA-Z0-9_ ]"))
  if i == none {
    return ()
  }
  let arrow = line.slice(0, i)
  line = line.slice(i).trim()

  let p2 = line.find(regex("^[a-zA-Z0-9_]+"))
  line = line.slice(p2.len()).trim()
  */

  //let comment = none
  let enable-dst = false
  let disable-src = false
  let create-dst = false
  let destroy-dst = false
  /*if line.contains(":") {
    (line, comment) = line.split(":")
    comment = comment.trim()
    line = line.trim()
  }*/
  if mods.contains("++") {
    enable-dst = true
  }
  if mods.contains("--") {
    disable-src = true
  }
  if mods.contains("**") {
    create-dst = true
  }
  if mods.contains("!!") {
    destroy-dst = true
  }

  // TODO start / end tips
  let seq-tips = parse-seq-tips(arrow)
  if seq-tips == none {
    return ()
  }
  let (start-tip, dashed, end-tip, flip) = seq-tips
  if flip and p1 == p2 {
    (start-tip, end-tip) = (end-tip, start-tip)
  }
  //panic(start-tip, dashed, end-tip)
  //comment += json.encode((start-tip, dashed, end-tip)).replace("\n", "")

  elmts += _seq(
    p1, p2,
    comment: comment,
    dashed: dashed,
    start-tip: start-tip,
    end-tip: end-tip,
    enable-dst: enable-dst,
    disable-src: disable-src,
    create-dst: create-dst,
    destroy-dst: destroy-dst,
    flip: flip
  )
  return elmts
}

#let from-plantuml(code, width: auto) = {
  let code = code.text
  code = code.replace(regex("(?s)/'.*?'/"), "")

  let elmts = ()
  let lines = code.split("\n")
  let group-stack = ()
  let note-data = none

  for line in lines {
    if note-data != none {
      let l = line.trim()
      if l in ("end note", "endrnote", "endhnote") {
        elmts += _note(
          note-data.side,
          note-data.lines.join("\n"),
          color: note-data.color,
          pos: note-data.pos,
          shape: note-data.shape,
          aligned: note-data.aligned
        )
        note-data = none
      } else {
        note-data.lines.push(line)
      }
      continue
    }

    line = line.trim()
    if line.len() == 0 { continue }

    if is-boundary-stmt(line) or is-comment-stmt(line) {
      continue
    } else if is-par-stmt(line) {
      elmts += parse-par-stmt(line)
    } else if is-gap-stmt(line) {
      elmts += parse-gap-stmt(line)
    } else if is-delay-stmt(line) {
      elmts += parse-delay-stmt(line)
    } else if is-sep-stmt(line) {
      elmts += parse-sep-stmt(line)
    } else if is-evt-stmt(line) {
      elmts += parse-evt-stmt(line)
    } else if is-ret-stmt(line) {
      elmts += parse-ret-stmt(line)
    } else if is-grp-stmt(line) {
      let group-data = parse-grp-stmt(line)
      group-data.insert("start-i", elmts.len())
      group-stack.push(group-data)
    } else if line == "end" {
      if group-stack.len() == 0 {
        continue
      }

      let data = group-stack.pop()

      if data.type in ("alt", "else") {
        let sections = ()
        let section-elmts = ()

        while true {
          section-elmts = elmts.slice(data.start-i)
          elmts = elmts.slice(0, data.start-i)
          sections.push(section-elmts)
          sections.push(data.desc)
          if data.type == "alt" {
            break

          } else if data.type != "else" {
            panic("Alt/else group mismatch")
          }
          data = group-stack.pop()
        }

        elmts += _alt(..sections.rev())
        continue
      }

      let grp-elmts = elmts.slice(data.start-i)
      elmts = elmts.slice(0, data.start-i)
      elmts += _grp(
        data.name,
        grp-elmts,
        desc: data.desc,
        type: data.type
      )
    } else if is-simple-note-stmt(line) {
      elmts += parse-simple-note-stmt(line)
    } else if is-multiline-note-stmt(line) {
      note-data = parse-multiline-note-stmt(line)
    } else {
      elmts += parse-seq-stmt(line)
    }
  }

  return diagram(elmts, width: width)
}