# i eventually want the shell to be a standalone program and shit

fn pad(text, width) -> string do
  let result = text

  while (result:len() < width)
    result = result ~ " "

  return result
end

fn help_row(label, description) do
  let column = pad(label, 22)

  if label:len() >= 22 do
    column = label ~ "  "
  end

  puts("    #{column}#{description}\n")
end

fn help_group(title, group_name) do
  puts("\n  #{title}\n")

  for index in 0..commands:len() do
    if commands[index].group == group_name do
      help_row(commands[index].usage, commands[index].help)
    end
  end
end

fn cmd_help(context) do
  help_group("shell", "shell")
  help_group("gils (builtin)", "gils")
  # gils scripts are real files in /bin, native programs in /usr/bin
  const scripts = fs:entries("/bin")
  if scripts != :nil do
    puts("\n  gils (/bin scripts)\n")
    for index in 0..scripts:len() do
      const name = scripts[index].name
      if (name:len() > 3 and name[(name:len() - 3)..] == ".rv") do help_row(name[0..(name:len() - 3)], "") end
    end
  end
  const progs = fs:entries("/usr/bin")
  if progs != :nil do
    puts("\n  programs (/usr/bin)\n")
    for index in 0..progs:len() do help_row(progs[index].name, "") end
  end

  puts("\n  fonts (font <name>)\n")
  for index in 0..fonts:len() do help_row(fonts[index].name, "8x#{fonts[index].height}") end
  const font_files = fs:entries("/usr/share")
  if font_files != :nil do
    puts("\n  fonts on disk (font load /usr/share/x.psf)\n")
    for index in 0..font_files:len() do help_row(font_files[index].name, "") end
  end

  puts("\n")
end

fn welcome() do
  let fs_status = "no filesystem"

  if fs.ready do
    fs_status = "revelfs mounted"
  end

  puts("\n")
  puts("   kernel written in revo - by an alcoholic\n")
  puts("   #{(mem_total() shr 20)} MiB ram | #{fs_status} | #{prog_count()} programs\n")
  puts("   type help to see what it does\n\n")
  puts(prompt())
end

# global so /bin scripts can call it from a nested eval fiber
global arg_name = fn(line, start) -> { name: string, rest: num } do
  let quoted = :false
  let begin = start

  if begin < line:len() and line[begin] == "\"" do
    begin += 1
    quoted = :true
  end

  let index = begin

  if quoted do
    while (index < line:len() and line[index] != "\"")
      index += 1
  end else do
    while (index < line:len() and line[index] != " ")
      index += 1
  end

  const name = line[begin..index]
  let rest = index

  if quoted and rest < line:len() do
    rest += 1
  end

  if rest < line:len() and line[rest] == " " do
    rest += 1
  end

  return { name = name, rest = rest }
end

fn parent_of(path) -> string do
  if path == "/" do
    return "/"
  end

  let index = path:len() - 1

  while (index > 0 and path[index] != "/")
    index -= 1

  if index == 0 do
    return "/"
  end

  return path[0..index]
end

fn cmd_cd(context) do
  const arg = if (context.argv:len() > 1) context.argv[1] else "/"

  const target = if (arg == "..") parent_of(wd.path) else expand_path(arg)

  if target == "/proc"
      or target == "/bin"
      or fs:is_dir(target) do
    wd.path = target
  end else do
    fail("cd: #{arg}: not a directory\n")
  end
end

fn cmd_pwd(context)
  puts("#{wd.path}\n")

fn wipe()
  console:clear()

fn cmd_clear(context)
  wipe()

fn zoom_by(delta) do
  const entry = console.font_entry

  # ttf is vector, stepping the size interactively is fine
  if entry != :nil and entry.kind == :ttf do
    let size = entry.size + delta * 4

    if (size < 8) size = 8
    if (size > 72) size = 72

    if size == entry.size do
      puts("zoom #{size}px\n")
      return :nil
    end

    const face = load_ttf(entry.path, size)

    if face == :nil do
      puts("zoom: rasterize failed\n")
      return :nil
    end

    add_font(entry.name, face.glyphs, face.width, face.height, :ttf, entry.path, size)
    console:set_font(find_font(entry.name))
    puts("zoom #{size}px\n")

    return :nil
  end

  # bitmap fonts js use integer pixel scale
  let scale = console.scale + delta

  if (scale < 1) scale = 1
  if (scale > 6) scale = 6

  console.scale = scale
  wipe()

  puts("zoom #{scale}x\n")
end

fn cmd_zoom(context) do
  const direction =
    if (context.argv:len() > 1)
      context.argv[1]
    else ""

  match direction
  | "in" => zoom_by(1)
  | "out" => zoom_by(-1)
  | _ => puts("usage: zoom in | zoom out\n")
end

fn font_basename(path) -> string do
  let start = 0
  let index = 0

  while (index < path:len()) do
    if path[index] == "/" do
      start = index + 1
    end

    index += 1
  end

  let name = path[start..]
  let dot = -1

  for i in 0..name:len() do
    if (name[i] == ".")
      dot = i
  end

  if (dot > 0)
    name = name[0..dot]

  return name
end

fn load_psf(path) -> { glyphs: table, width: num, height: num } | :nil do
  const size = fs:size(path)

  if size < 4 do
    return :nil
  end

  const data = fs:read_bytes(path, 0, size)

  if data[0]:ascii() != 0x36 or data[1]:ascii() != 0x04 do
    return :nil
  end

  const height = data[3]:ascii()

  if height == 0 or size < 4 + 128 * height do
    return :nil
  end

  let glyphs = {}

  for code in 32..128 do
    const base = 4 + code * height
    let rows = {}

    for row in 0..height do
      rows:push(reverse8(data[base + row]:ascii()))
    end

    glyphs:push(rows)
  end

  return { glyphs = glyphs, width = 8, height = height }
end

fn has_slash(text) -> bool do
  for index in 0..text:len() do
    if (text[index] == "/")
      return :true
  end

  return :false
end

fn ends_with(text, suffix) -> bool do
  if text:len() < suffix:len() do
    return :false
  end

  return text[(text:len() - suffix:len())..] == suffix
end

fn str_to_int(text) -> num do
  let value = 0

  for index in 0..text:len() do
    const code = text[index]:ascii()

    if code >= 48 and code <= 57 do
      value = value * 10 + (code - 48)
    end
  end

  return value
end

#* resolve a font name to a path and a kind *#
fn font_file(name) -> { path: string, kind: ( :ttf | :psf | :none ) } do
  return match
  | has_slash(name) => do
      const p = expand_path(name)

      if ends_with(p, ".ttf") and fs:size(p) >= 0 do
        return { path = p, kind = :ttf }
      end

      if ends_with(p, ".psf") and fs:size(p) >= 0 do
        return { path = p, kind = :psf }
      end

      if fs:size(p ~ ".ttf") >= 0 do
        return { path = p ~ ".ttf", kind = :ttf }
      end

      if fs:size(p ~ ".psf") >= 0 do
        return { path = p ~ ".psf", kind = :psf }
      end

      return { path = p, kind = :none }
    end
  | fs:size("/usr/share/#{name}.psf") >= 0 => { path = "/usr/share/#{name}.psf", kind = :psf }
  | fs:size("/usr/share/#{name}.ttf") >= 0 => { path = "/usr/share/#{name}.ttf", kind = :ttf }
  | _ => { path = name, kind = :none }
end

fn cmd_font(context) do
  if context.argv:len() < 2 do
    puts("fonts:")

    for index in 0..fonts:len() do
      puts(" #{fonts[index].name}(#{fonts[index].width}x#{fonts[index].height})")
    end

    puts("\n")
    const font_files = fs:entries("/usr/share")
    if font_files != :nil do
      puts("on disk:")

      for index in 0..font_files:len() do
        puts(" #{font_files[index].name}")
      end

      puts("\n")
    end

    return :nil
  end

  # `font load <path> [size]` still works, but a bare name/path is the same thing
  let name = context.argv[1]
  let arg_at = 1

  if name == "load" do
    if context.argv:len() < 3 do
      puts("usage: font load <path> [size]\n")
      return :nil
    end

    name = context.argv[2]
    arg_at = 2
  end

  # an explicit size (ttf only) forces a fresh rasterize. without one we just
  # switch to whatever is already in the registry under that name
  let size = 0

  if context.argv:len() > arg_at + 1 do
    size = str_to_int(context.argv[arg_at + 1])
  end

  if size == 0 do
    const existing = find_font(name)

    if existing != :nil do
      console:set_font(existing)
      return :nil
    end
  end

  const info = font_file(name)

  if info.kind == :none do
    puts("font: #{name}: no such font\n")
    return :nil
  end

  const reg_name = font_basename(info.path)

  if info.kind == :psf do
    const prior = find_font(reg_name)

    if prior != :nil do
      console:set_font(prior)
      return :nil
    end

    const parsed = load_psf(info.path)

    if parsed == :nil do
      puts("font: #{name}: not a psf font\n")
      return :nil
    end

    add_font(reg_name, parsed.glyphs, parsed.width, parsed.height, :bitmap, :nil, 0)
    console:set_font(find_font(reg_name))

    return :nil
  end

  # ttf: rasterize ascii at the requested size (default 18)
  if size == 0 do
    size = 18
  end

  const face = load_ttf(info.path, size)

  if face == :nil do
    puts("font: #{name}: bad ttf\n")
    return :nil
  end

  add_font(reg_name, face.glyphs, face.width, face.height, :ttf, info.path, size)
  console:set_font(find_font(reg_name))
end

fn bcd(byte) -> num do
  return (byte shr 4) * 10 + (byte band 15)
end

fn rtc(cmos_reg) -> num do
  outb(0x70, cmos_reg)
  return inb(0x71)
end

fn cmd_time(context) do
  const hour = 4 |> rtc |> bcd
  const min = 2 |> rtc |> bcd
  const sec = 0 |> rtc |> bcd

  puts("utc #{hour}:#{min}:#{sec}\n")
end

#* 0x prefixed 16 digit hex *#
fn hex(value) -> string do
  const digits = "0123456789abcdef"
  let result = ""

  for index in 0..16 do
    result = result ~ digits[(value shr ((15 - index) * 4)) band 15]
  end

  return "0x#{result}"
end

fn mem_type_name(kind) -> string do
  match kind
  | 0 => "usable"
  | 1 => "reserved"
  | 2 => "acpi-reclaimable"
  | 3 => "acpi-nvs"
  | 4 => "bad"
  | 5 => "bootloader-reclaimable"
  | 6 => "kernel+modules"
  | 7 => "framebuffer"
  | _ => "unknown"
end

#* the boot memory map dump *#
fn dump_memmap() do
  puts("memory map:\n")

  for index in 0..memmap_count() do
    puts("  #{hex(memmap_base(index))} len=#{hex(memmap_len(index))} type=#{mem_type_name(memmap_kind(index))}\n")
  end

  puts("usable: #{(mem_total() shr 20)} MiB, free: #{(mem_free() shr 20)} MiB\n")
end

fn cmd_mem(context)
  puts("#{(mem_free() shr 20)} MiB free / #{(mem_total() shr 20)} MiB usable\n")

fn cmd_uptime(context)
  puts("#{math.floor(uptime() / 100)}s (#{uptime()} ticks)\n")

fn cmd_ps(context)
  puts("#{proc_count()} process(es) running\n")

fn cmd_echo(context) do
  if context.line:len() > 5 do
    puts("#{context.line[5..]}\n")
  end else do
    puts("\n")
  end
end

fn cmd_mkfs(context)
  fs:format()

#* resolve a command name to a path and a kind *#
fn exec_file(target) -> { path: string, kind: ( :elf | :script | :none ) } do
  let candidates = {}

  if has_slash(target) do
    candidates:push(expand_path(target))
    candidates:push(expand_path(target) ~ ".rv")
  end else do
    candidates:push(expand_path(target))
    candidates:push(expand_path(target) ~ ".rv")
    candidates:push("/usr/bin/#{target}")
    candidates:push("/bin/#{target}.rv")
  end

  for index in 0..candidates:len() do
    const path = candidates[index]

    if fs:size(path) >= 0 do
      const head = fs:read_bytes(path, 0, 4)

      if head:len() >= 4
          and head[0]:ascii() == 127
          and head[1]:ascii() == 69
          and head[2]:ascii() == 76
          and head[3]:ascii() == 70 do
        return { path = path, kind = :elf }
      end

      return { path = path, kind = :script }
    end
  end

  return { path = target, kind = :none }
end

fn cmd_run(context) do
  if context.argv:len() <= 1 do
    list_progs()
    return :nil
  end

  const target = context.argv[1]
  const info = exec_file(target)

  if info.kind == :none do
    fail("run: #{target}: not found\n")
    return :nil
  end

  const sub_argv = context.rest:split(" ")
  const sub_ctx = make_ctx(context.rest, sub_argv)

  if info.kind == :script do
    run_script_path(info.path, target, sub_ctx)

    return :nil
  end

  if load_file_elf(info.path, sub_ctx.rest) == :true do
    return :hold
  end

  fail("run: #{target}: not executable\n")

  return :nil
end

#* run one shell line *#
fn run(line) -> :nil do
  # the fact that the shell needs to interface directly with ed isnt, very nice
  # this is a TODO btw
  if gils_ed_active() do
    gils_ed_feed(line)
    return :nil
  end

  if line:trim():len() == 0 do
    puts(prompt())
    return :nil
  end

  const argv = line:split(" ")
  const context = make_ctx(line, argv)
  shell_status.code = 0
  const command = lookup(argv[0])

  if command != :nil do
    # :hold means the command took over (modal editor / launched a program) so
    # we dont draw a fresh prompt, otherwise we do
    const result = command.handler(context)

    if result != :hold do
      puts(prompt())
    end

    return :nil
  end

  if run_script(argv[0], context) == :true do
    puts(prompt())
    return :nil
  end

  if run_prog(argv[0], context.rest) == :true do
    return :nil
  end

  shell_status.code = 127
  puts("#{argv[0]}: command not found\n")
  puts(prompt())
end

register("help", "shell", "show this", cmd_help)
register("clear", "shell", "wipe the screen", cmd_clear)
register("time", "shell", "utc clock", cmd_time)
register("mem", "shell", "free / total ram", cmd_mem)
register("uptime", "shell", "seconds since boot", cmd_uptime)
register("ps", "shell", "running processes", cmd_ps)
register("zoom in|out", "shell", "scale the font", cmd_zoom)
register("font [name] [size]", "shell", "switch/load a console font (psf or ttf)", cmd_font)
register("echo <text>", "shell", "print it back", cmd_echo)
register("mkfs", "shell", "format the disk", cmd_mkfs)
register("cd <path>", "gils", "change directory", cmd_cd)
register("pwd", "gils", "print working dir", cmd_pwd)
register("run <path> [args]", "shell", "run a program or revo script", cmd_run)