# this is just a simple prompt to test that shit is working

fn pad(s, width) do
  let out = s
  while out:len() < width do out = out ~ " " end
  return out
end

fn help_row(cmd, desc) puts("    #{pad(cmd, 20)}#{desc}\n")

fn cmd_help() do
  puts("\n  shell\n")
  help_row("help", "show this")
  help_row("clear", "wipe the screen")
  help_row("time", "utc clock")
  help_row("mem", "free / total ram")
  help_row("uptime", "seconds since boot")
  help_row("ps", "running processes")
  help_row("zoom in|out", "scale the font")
  help_row("echo <text>", "print it back")
  puts("\n  files\n")
  help_row("ls", "list files")
  help_row("cat <name>", "print a file")
  help_row("write <name> <text>", "create or overwrite")
  help_row("rm <name>", "delete a file")
  help_row("mkfs", "format the disk")
  puts("\n  programs\n")
  help_row("run", "list programs")
  help_row("run <name>", "")
  puts("\n")
end

fn welcome() do
  let fsline = "no filesystem"
  if fs.ready do fsline = "revelfs mounted" end
  puts("\n")
  puts("   a tiny os whose brain lives in revo, zig only touches the metal\n")
  puts("   #{(mem_total() shr 20)} MiB ram | #{fsline} | #{prog_count()} programs\n")
  puts("   type help to see what it does\n\n% ")
end

fn arg_name(line, start) do
  let quoted = :false
  let begin = start
  if (begin < line:len() and line[begin] == "\"") do begin += 1 quoted = :true end
  # scan to the end of the name, a closing quote or a space depending on how it opened
  let i = begin
  if quoted do
    while (i < line:len() and line[i] != "\"") do i += 1 end
  end
  else do
    while (i < line:len() and line[i] != " ") do i += 1 end
  end
  const name = line[begin..i]
  # step past the closing quote and the separating space so rest points at the text
  let rest = i
  if (quoted and rest < line:len()) do rest += 1 end
  if (rest < line:len() and line[rest] == " ") do rest += 1 end
  { name = name, rest = rest }
end

fn cmd_write(line) do
  const a = arg_name(line, 6)
  if a.name:len() == 0 do puts("usage: write <name> <text>\n") return :nil end
  fs:write(a.name, line[a.rest..])
end

fn cmd_cat(line) do
  const a = arg_name(line, 4)
  if a.name:len() == 0 do puts("usage: cat <name>\n") return :nil end
  fs:cat(a.name)
end

fn cmd_rm(line) do
  const a = arg_name(line, 3)
  if a.name:len() == 0 do puts("usage: rm <name>\n") return :nil end
  fs:rm(a.name)
end

fn zoom_by(delta) do
  let scale = con.scale + delta
  if scale < 1 do scale = 1 end
  if scale > 6 do scale = 6 end
  con.scale = scale
  cmd_clear()
  puts("zoom #{scale}x\n")
end

fn cmd_zoom(words) do
  const dir = if words:len() > 1 words[1] else ""
  if dir == "in" do zoom_by(1) end
  else if dir == "out" do zoom_by(-1) end
  else do puts("usage: zoom in | zoom out\n") end
end

fn cmd_clear() con:clear()

fn bcd(byte) (byte shr 4) * 10 + (byte band 15)
fn rtc(reg) do
  outb(0x70, reg)
  inb(0x71)
end
fn cmd_time() puts("utc #{bcd(rtc(4))}:#{bcd(rtc(2))}:#{bcd(rtc(0))}\n")

# 0x prefixed 16 digit hex
fn hex(n) do
  const digits = "0123456789abcdef"
  let out = ""
  for i in 0..16 do out = out ~ digits[(n shr ((15 - i) * 4)) band 15] end
  "0x#{out}"
end

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

# the boot memory map dump
fn dump_memmap() do
  puts("memory map:\n")
  for i in 0..memmap_count() do
    puts("  #{hex(memmap_base(i))} len=#{hex(memmap_len(i))} type=#{mem_type_name(memmap_kind(i))}\n")
  end
  puts("usable: #{(mem_total() shr 20)} MiB, free: #{(mem_free() shr 20)} MiB\n")
end

fn cmd_mem() puts("#{(mem_free() shr 20)} MiB free / #{(mem_total() shr 20)} MiB usable\n")
fn cmd_uptime() puts("#{math.floor(uptime() / 100)}s (#{uptime()} ticks)\n")
fn cmd_ps() puts("#{proc_count()} process(es) running\n")

fn run(line) do
  if line:trim():len() == 0 do puts("% ") return :nil end
  const words = line:split(" ")
  const cmd = words[0]
  if cmd == "run" do
    if words:len() <= 1 do list_progs() puts("% ") return :nil end
    if run_prog(words[1]) == :true return :nil
    puts("% ")
    return :nil
  end
  match cmd
    | "help" => cmd_help()
    | "clear" => cmd_clear()
    | "time" => cmd_time()
    | "mem" => cmd_mem()
    | "uptime" => cmd_uptime()
    | "ps" => cmd_ps()
    | "zoom" => cmd_zoom(words)
    | "mkfs" => fs:format()
    | "ls" => fs:ls()
    | "cat" => cmd_cat(line)
    | "write" => cmd_write(line)
    | "rm" => cmd_rm(line)
    | "echo" => if line:len() > 5 puts("#{line[5..]}\n") else puts("\n")
    | _ => puts("unknown command: #{cmd}\n")
  puts("% ")
end