Cli.fish_engine: def of cli@0.2.0.0
Import: import cli@0.2.0.0/cli.bend as Cli
Lines 7223-7292 of cli@0.2.0.0/cli.bend: https://jend.leeeet.dev/read.txt?path=cli@0.2.0.0/cli.bend&start_line=7223&end_line=7292

import Base

# The function every fish script shares, for function prefix id: it walks
# the words before the cursor as the bash engine does.
def fish_engine(+id: String) -> List<&2, String>:
  [
    "",
    "# Succeeds when the words before the cursor reach path $argv[1] and the next",
    "# word can be one of $argv[2..-1]: n, an option or subcommand; h, a",
    "# subcommand after help; v, an option's value; p<k>, positional slot k.",
    String.concat(["function ", id, "_is"]),
    "    # fish 4 deprecates -o, which fish 3 needs.",
    "    set -l words (commandline -xpc 2>/dev/null; or commandline -opc)",
    "    set -e words[1]",
    "    set -l path 0",
    String.concat(["    set -l shape (", id, "_shape 0 | string split ' ')"]),
    "    set -l want 0",
    "    set -l end 0",
    "    set -l help 0",
    "    set -l n 0",
    "    for word in $words",
    "        if test $want = 1",
    "            set want 0",
    "        else if test $end = 0; and test \"$word\" = --",
    "            set end 1",
    "        else if test $end = 0; and string match -q -r -- '^--.' $word",
    String.concat(["            if not string match -q -- '*=*' $word; and ", id, "_valued $path $word"]),
    "                set want 1",
    "            end",
    "        else if test $end = 0; and string match -q -r -- '^-.' $word",
    "            set -l chars (string split '' -- (string sub -s 2 -- $word))",
    "            for i in (seq (count $chars))",
    String.concat(["                if ", id, "_valued $path -$chars[$i]"]),
    "                    test $i = (count $chars); and set want 1",
    "                    break",
    "                end",
    "            end",
    "        else if test $shape[1] = 1",
    "            if test $end = 1",
    "                return 1",
    "            else if test $help = 0; and test \"$word\" = help",
    "                set help 1",
    "            else",
    String.concat(["                set path (", id, "_dest $path $word); or return 1"]),
    String.concat(["                set shape (", id, "_shape $path | string split ' ')"]),
    "            end",
    "        else",
    "            # n counts the slots filled. The variadic slot stays open, but a",
    "            # rest() value takes every later word, so nothing more completes.",
    "            set n (math $n + 1)",
    "            if test $n = $shape[2]; and test $shape[3] = 1",
    "                set end 1",
    "            else if test $n = $shape[2]",
    "                set n (math $n - 1)",
    "            end",
    "        end",
    "    end",
    "    test $path = $argv[1]; or return 1",
    "    set -l tags",
    "    if test $want = 1",
    "        set tags v",
    "    else",
    "        test $end = 0; and test $help = 0; and set -a tags n",
    "        test $end = 0; and test $help = 1; and set -a tags h",
    "        test $shape[1] = 0; and test $help = 0; and set -a tags p(math $n + 1)",
    "    end",
    "    for tag in $argv[2..-1]",
    "        contains -- $tag $tags; and return 0",
    "    end",
    "    return 1",
    "end",
  ]

Uses (3):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=String
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=String.concat