type environment {
  screen: (handle screen)
  program: (handle program)
  cursor-word: (handle word)
  nrows: int
  ncols: int
  code-separator-col: int
}

fn initialize-environment _env: (addr environment) {
  var env/esi: (addr environment) <- copy _env
  var program-ah/eax: (addr handle program) <- get env, program
  allocate program-ah
  var program/eax: (addr program) <- lookup *program-ah
  var cursor-word-ah/ecx: (addr handle word) <- get env, cursor-word
  initialize-program program, cursor-word-ah
  # initialize screen
  var screen-ah/eax: (addr handle screen) <- get env, screen
  var _screen/eax: (addr screen) <- lookup *screen-ah
  var screen/edi: (addr screen) <- copy _screen
  var nrows/eax: int <- copy 0
  var ncols/ecx: int <- copy 0
  nrows, ncols <- screen-size screen
  var dest/edx: (addr int) <- get env, nrows
  copy-to *dest, nrows
  dest <- get env, ncols
  copy-to *dest, ncols
  var repl-col/ecx: int <- copy ncols
  repl-col <- shift-right 1
  dest <- get env, code-separator-col
  copy-to *dest, repl-col
}

fn draw-screen _env: (addr environment) {
  var env/esi: (addr environment) <- copy _env
  var screen-ah/eax: (addr handle screen) <- get env, screen
  var _screen/eax: (addr screen) <- lookup *screen-ah
  var screen/edi: (addr screen) <- copy _screen
  var dest/edx: (addr int) <- get env, code-separator-col
  var tmp/eax: int <- copy *dest
  clear-canvas env
  tmp <- add 2  # repl-margin-left
  move-cursor screen, 3, tmp  # input-row
}

fn initialize-environment-with-fake-screen _self: (addr environment), nrows: int, ncols: int {
  var self/esi: (addr environment) <- copy _self
  var screen-ah/eax: (addr handle screen) <- get self, screen
  allocate screen-ah
  var screen-addr/eax: (addr screen) <- lookup *screen-ah
  initialize-screen screen-addr, nrows, ncols
  initialize-environment self
}

fn process _self: (addr environment), key: grapheme {
$process:body: {
    var self/esi: (addr environment) <- copy _self
    compare key, 0x445b1b  # left-arrow
    {
      break-if-!=
      var cursor-word-ah/edi: (addr handle word) <- get self, cursor-word
      var _cursor-word/eax: (addr word) <- lookup *cursor-word-ah
      var cursor-word/ecx: (addr word) <- copy _cursor-word
      # if not at start, move left within current word
      var at-start?/eax: boolean <- cursor-at-start? cursor-word
      compare at-start?, 0  # false
      {
        break-if-=
        cursor-left cursor-word
        break $process:body
      }
      # otherwise, move to end of prev word
      var prev-word-ah/esi: (addr handle word) <- get cursor-word, prev
      var prev-word/eax: (addr word) <- lookup *prev-word-ah
      {
        compare prev-word, 0
        break-if-=
        copy-object prev-word-ah, cursor-word-ah
        cursor-to-end prev-word
      }
      break $process:body
    }
    compare key, 0x435b1b  # right-arrow
    {
      break-if-!=
      var cursor-word-ah/edi: (addr handle word) <- get self, cursor-word
      var _cursor-word/eax: (addr word) <- lookup *cursor-word-ah
      var cursor-word/ecx: (addr word) <- copy _cursor-word
      # if not at end, move right within current word
      var at-end?/eax: boolean <- cursor-at-end? cursor-word
      compare at-end?, 0  # false
      {
        break-if-=
        cursor-right cursor-word
        break $process:body
      }
      # otherwise, move to start of next word
      var next-word-ah/esi: (addr handle word) <- get cursor-word, next
      var next-word/eax: (addr word) <- lookup *next-word-ah
      {
        compare next-word, 0
        break-if-=
        copy-object next-word-ah, cursor-word-ah
        cursor-to-start next-word
      }
      break $process:body
    }
    compare key, 0x7f  # del (backspace on Macs)
    {
      break-if-!=
      var cursor-word-ah/edi: (addr handle word) <- get self, cursor-word
      var _cursor-word/eax: (addr word) <- lookup *cursor-word-ah
      var cursor-word/ecx: (addr word) <- copy _cursor-word
      # if not at start of some word, delete grapheme before cursor within current word
      var at-start?/eax: boolean <- cursor-at-start? cursor-word
      compare at-start?, 0  # false
      {
        break-if-=
        delete-before-cursor cursor-word
        break $process:body
      }
      # otherwise delete current word and move to end of prev word
      var prev-word-ah/esi: (addr handle word) <- get cursor-word, prev
      var prev-word/eax: (addr word) <- lookup *prev-word-ah
      {
        compare prev-word, 0
        break-if-=
        copy-object prev-word-ah, cursor-word-ah
        cursor-to-end prev-word
        delete-next prev-word
      }
      break $process:body
    }
    compare key, 0x20  # space
    {
      break-if-!=
      # insert new word
      var cursor-word-ah/edx: (addr handle word) <- get self, cursor-word
      append-word cursor-word-ah
      var cursor-word/eax: (addr word) <- lookup *cursor-word-ah
      var next-word-ah/ecx: (addr handle word) <- get cursor-word, next
      copy-object next-word-ah, cursor-word-ah
      break $process:body
    }
    compare key, 0xa  # enter
    {
      break-if-!=
      # toggle display of subsidiary stack
      var cursor-word-ah/edx: (addr handle word) <- get self, cursor-word
      var cursor-word/eax: (addr word) <- lookup *cursor-word-ah
      var display-subsidiary-stack?/eax: (addr boolean) <- get cursor-word, display-subsidiary-stack?
      var tmp/ecx: int <- copy 1
      tmp <- subtract *display-subsidiary-stack?
      copy-to *display-subsidiary-stack?, tmp
      break $process:body
    }
    # otherwise insert key within current word
    var g/edx: grapheme <- copy key
    var print?/eax: boolean <- real-grapheme? key
    {
      compare print?, 0  # false
      break-if-=
      var cursor-word-ah/eax: (addr handle word) <- get self, cursor-word
      var cursor-word/eax: (addr word) <- lookup *cursor-word-ah
      add-grapheme-to-word cursor-word, g
      break $process:body
    }
    # silently ignore other hotkeys
}
}

fn evaluate-environment _env: (addr environment), stack: (addr value-stack) {
  var env/esi: (addr environment) <- copy _env
  # program
  var program-ah/eax: (addr handle program) <- get env, program
  var _program/eax: (addr program) <- lookup *program-ah
  var program/esi: (addr program) <- copy _program
  # defs
  var defs/edx: (addr handle function) <- get program, defs
  # line
  var sandbox-ah/esi: (addr handle sandbox) <- get program, sandboxes
  var sandbox/eax: (addr sandbox) <- lookup *sandbox-ah
  var line-ah/eax: (addr handle line) <- get sandbox, data
  var _line/eax: (addr line) <- lookup *line-ah
  var line/esi: (addr line) <- copy _line
  evaluate defs, 0, line, 0, stack
}

fn render _env: (addr environment) {
  var env/esi: (addr environment) <- copy _env
  clear-canvas env
  var screen-ah/edi: (addr handle screen) <- get env, screen
  var _screen/eax: (addr screen) <- lookup *screen-ah
  var screen/edi: (addr screen) <- copy _screen
  var _repl-col/ecx: (addr int) <- get env, code-separator-col
  var repl-col/ecx: int <- copy *_repl-col
  repl-col <- add 2  # repl-margin-left
  # cursor-word
  var cursor-word-ah/ebx: (addr handle word) <- get env, cursor-word
  var _cursor-word/eax: (addr word) <- lookup *cursor-word-ah
  var cursor-word/ebx: (addr word) <- copy _cursor-word
  # program
  var program-ah/eax: (addr handle program) <- get env, program
  var _program/eax: (addr program) <- lookup *program-ah
  var program/esi: (addr program) <- copy _program
  # defs
  var defs/edx: (addr handle function) <- get program, defs
  # line
  var sandbox-ah/esi: (addr handle sandbox) <- get program, sandboxes
  var sandbox/eax: (addr sandbox) <- lookup *sandbox-ah
  var line-ah/eax: (addr handle line) <- get sandbox, data
  var _line/eax: (addr line) <- lookup *line-ah
  var line/esi: (addr line) <- copy _line
  # cursor-col
  var cursor-col: int
  var cursor-col-a/eax: (addr int) <- address cursor-col
  #
  var dummy/ecx: int <- render-line screen, defs, 0, line, 3, repl-col, cursor-word, cursor-col-a  # input-row=3
  move-cursor screen, 3, cursor-col  # input-row
}

fn render-line screen: (addr screen), defs: (addr handle function), bindings: (addr table), _line: (addr line), top-row: int, left-col: int, cursor-word: (addr word), cursor-col-a: (addr int) -> right-col/ecx: int {
  # curr-word
  var line/esi: (addr line) <- copy _line
  var first-word-ah/eax: (addr handle word) <- get line, data
  var curr-word/eax: (addr word) <- lookup *first-word-ah
  # loop-carried dependency
  var curr-col/ecx: int <- copy left-col
  #
  {
    compare curr-word, 0
    break-if-=
    # if necessary, first render columns for subsidiary stack
    $render-line:subsidiary: {
      {
        var display-subsidiary-stack?/eax: (addr boolean) <- get curr-word, display-subsidiary-stack?
        compare *display-subsidiary-stack?, 0  # false
        break-if-= $render-line:subsidiary
      }
      # does function exist?
      var callee/edi: (addr function) <- copy 0
      {
        var curr-stream-storage: (stream byte 0x10)
        var curr-stream/esi: (addr stream byte) <- address curr-stream-storage
        emit-word curr-word, curr-stream
        var callee-h: (handle function)
        var callee-ah/eax: (addr handle function) <- address callee-h
        find-function defs, curr-stream, callee-ah
        var _callee/eax: (addr function) <- lookup *callee-ah
        callee <- copy _callee
        compare callee, 0
        break-if-= $render-line:subsidiary
      }
      move-cursor screen, top-row, curr-col
      print-word screen, curr-word
      {
        var word-len/eax: int <- word-length curr-word
        curr-col <- add word-len
        curr-col <- add 2
        add-to top-row, 1
      }
      # obtain stack at call site
      var stack-storage: value-stack
      var stack/edx: (addr value-stack) <- address stack-storage
      initialize-value-stack stack, 0x10
      {
        var prev-word-ah/eax: (addr handle word) <- get curr-word, prev
        var prev-word/eax: (addr word) <- lookup *prev-word-ah
        compare prev-word, 0
        break-if-=
        evaluate defs, bindings, line, prev-word, stack
      }
      # construct new bindings
      var callee-bindings-storage: table
      var callee-bindings/esi: (addr table) <- address callee-bindings-storage
      initialize-table callee-bindings, 0x10
      bind-args callee, stack, callee-bindings
      # obtain body
      var callee-body-ah/eax: (addr handle line) <- get callee, body
      var callee-body/eax: (addr line) <- lookup *callee-body-ah
      # - render subsidiary stack
      curr-col <- render-line screen, defs, callee-bindings, callee-body, top-row, curr-col, cursor-word, cursor-col-a
      #
      move-cursor screen, top-row, curr-col
      print-code-point screen, 0x21d7  # ⇗
      #
      curr-col <- add 2
      subtract-from top-row, 1
    }
    # now render main column
    curr-col <- render-column screen, defs, bindings, line, curr-word, top-row, curr-col, cursor-word, cursor-col-a
    var next-word-ah/edx: (addr handle word) <- get curr-word, next
    curr-word <- lookup *next-word-ah
    loop
  }
  right-col <- copy curr-col
}

# Render:
#   - starting at top-row, left-col: final-word
#   - starting somewhere below at left-col: the stack result from interpreting first-world to final-word (inclusive)
#     unless final-word is truly the final word, in which case it might be incomplete
#
# Outputs:
# - Return the farthest column written.
# - If final-word is same as cursor-word, do some additional computation to set
#   cursor-col-a.
fn render-column screen: (addr screen), defs: (addr handle function), bindings: (addr table), scratch: (addr line), final-word: (addr word), top-row: int, left-col: int, cursor-word: (addr word), cursor-col-a: (addr int) -> right-col/ecx: int {
  var max-width/ecx: int <- copy 0
  {
    # indent stack
    var indented-col/ebx: int <- copy left-col
    indented-col <- add 1  # margin-right - 2 for padding spaces
    # compute stack
    var stack: value-stack
    var stack-addr/edi: (addr value-stack) <- address stack
    initialize-value-stack stack-addr, 0x10  # max-words
    evaluate defs, bindings, scratch, final-word, stack-addr
    # render stack
    var curr-row/edx: int <- copy top-row
    curr-row <- add 3  # stack-margin-top
    var _max-width/eax: int <- value-stack-max-width stack-addr
    var max-width/esi: int <- copy _max-width
    var i/eax: int <- value-stack-length stack-addr
    {
      compare i, 0
      break-if-<=
      move-cursor screen, curr-row, indented-col
      {
        var val/eax: int <- pop-int-from-value-stack stack-addr
        render-integer screen, val, max-width
        var size/eax: int <- decimal-size val
        compare size, max-width
        break-if-<=
        max-width <- copy size
      }
      curr-row <- increment
      i <- decrement
      loop
    }
  }

  # render word, initialize result
  reset-formatting screen
  move-cursor screen, top-row, left-col
  print-word screen, final-word
  {
    var size/eax: int <- word-length final-word
    compare size, max-width
    break-if-<=
    max-width <- copy size
  }

  # update cursor
  {
    var f/eax: (addr word) <- copy final-word
    compare f, cursor-word
    break-if-!=
    var cursor-index/eax: int <- cursor-index cursor-word
    cursor-index <- add left-col
    var dest/edi: (addr int) <- copy cursor-col-a
    copy-to *dest, cursor-index
  }

  # post-process right-col
  right-col <- copy max-width
  right-col <- add left-col
  right-col <- add 3  # margin-right
}

# synaesthesia
fn render-integer screen: (addr screen), val: int, max-width: int {
  var bg/eax: int <- hash-color val
  var fg/ecx: int <- copy 7
  {
    compare bg, 2
    break-if-!=
    fg <- copy 0
  }
  {
    compare bg, 3
    break-if-!=
    fg <- copy 0
  }
  {
    compare bg, 6
    break-if-!=
    fg <- copy 0
  }
  start-color screen, fg, bg
  print-grapheme screen, 0x20  # space
  print-int32-decimal-right-justified screen, val, max-width
  print-grapheme screen, 0x20  # space
}

fn hash-color val: int -> result/eax: int {
  result <- try-modulo val, 7  # assumes that 7 is always the background color
}

fn clear-canvas _env: (addr environment) {
  var env/esi: (addr environment) <- copy _env
  var screen-ah/edi: (addr handle screen) <- get env, screen
  var _screen/eax: (addr screen) <- lookup *screen-ah
  var screen/edi: (addr screen) <- copy _screen
  clear-screen screen
  var nrows/eax: (addr int) <- get env, nrows
  var _repl-col/ecx: (addr int) <- get env, code-separator-col
  var repl-col/ecx: int <- copy *_repl-col
  draw-vertical-line screen, 1, *nrows, repl-col
  move-cursor screen, 3, 2
  print-string screen, "x 2* = 2 x *"
}

fn real-grapheme? g: grapheme -> result/eax: boolean {
  result <- copy 1  # true
}