local component = require("component")
local fs = require("filesystem")
local term = require("term")
local computer = require("computer")

if not component.isAvailable("internet") then
  io.stderr:write("internet component is not available\n")
  return
end

local internet = component.internet

local args = {...}
local baseUrl = args[1] or "http://192.168.1.103/video/"
local outDir = args[2] or "video"

if baseUrl:sub(-1) ~= "/" then
  baseUrl = baseUrl .. "/"
end

local function u32be(s, off)
  return s:byte(off)   * 0x1000000
       + s:byte(off+1) * 0x10000
       + s:byte(off+2) * 0x100
       + s:byte(off+3)
end

local function formatBytes(n)
  if n >= 1024 * 1024 then
    return string.format("%.2f MB", n / 1024 / 1024)
  end
  if n >= 1024 then
    return string.format("%.1f KB", n / 1024)
  end
  return tostring(n) .. " B"
end

local function ensureDir(path)
  if not fs.exists(path) then
    fs.makeDirectory(path)
  end
end

local function download(url, path, label, index, total)
  print(string.format("[%d/%d] Requesting %s", index, total, url))

  local handle, err = internet.request(url)
  if not handle then
    return false, tostring(err)
  end

  if type(handle) ~= "function" and handle.finishConnect then
    local connected = false
    local started = computer.uptime()
    while computer.uptime() - started < 10 do
      local ok, result = pcall(handle.finishConnect)
      if ok and result then
        connected = true
        break
      end
      computer.pullSignal(0.05)
    end
    if not connected then
      pcall(handle.close)
      return false, "connection timeout"
    end
  end

  local file, ferr = io.open(path, "wb")
  if not file then
    if type(handle) ~= "function" then
      pcall(handle.close)
    end
    return false, tostring(ferr)
  end

  local downloaded = 0
  local t0 = computer.uptime()
  local lastDraw = 0
  local lastData = computer.uptime()

  while true do
    local chunk
    if type(handle) == "function" then
      chunk = handle()
    elseif handle.read then
      chunk = handle.read()
    else
      file:close()
      return false, "unsupported internet response handle"
    end

    if not chunk then
      if type(handle) == "function" then
        break
      end
      if downloaded > 0 and computer.uptime() - lastData > 1 then
        break
      end
      if downloaded == 0 and computer.uptime() - t0 > 10 then
        file:close()
        pcall(handle.close)
        return false, "empty response timeout"
      end
      computer.pullSignal(0.05)
    else
      file:write(chunk)
      downloaded = downloaded + #chunk
      lastData = computer.uptime()
    end

    local now = computer.uptime()
    if now - lastDraw >= 0.2 then
      lastDraw = now
      local _, y = term.getCursor()
      term.setCursor(1, y)
      term.clearLine()
      io.write(string.format("[%d/%d] %s: %s", index, total, label, formatBytes(downloaded)))
      io.flush()
      computer.pullSignal(0)
    end
  end

  file:close()
  if type(handle) ~= "function" then
    pcall(handle.close)
  end

  if downloaded <= 0 then
    if fs.exists(path) then
      fs.remove(path)
    end
    return false, "empty response"
  end

  local dt = computer.uptime() - t0
  local _, y = term.getCursor()
  term.setCursor(1, y)
  term.clearLine()
  print(string.format("[%d/%d] %s: %s in %.1fs", index, total, label, formatBytes(downloaded), dt))
  return true, nil
end

ensureDir(outDir)

term.clear()
print("OCV video downloader")
print("URL : " .. baseUrl)
print("DIR : " .. outDir)
print("")

local indexPath = fs.concat(outDir, "index.ocv")
local ok, err = download(baseUrl .. "index.ocv", indexPath, "index.ocv", 1, 1)
if not ok then
  io.stderr:write("download failed: " .. tostring(err) .. "\n")
  return
end

local f = io.open(indexPath, "rb")
if not f then
  io.stderr:write("cannot open downloaded index\n")
  return
end

local header = f:read(32)
f:close()

local magic = header and header:sub(1, 4) or ""
if not header or #header < 32 or (magic ~= "OCV3" and magic ~= "OCV4") then
  io.stderr:write("bad index.ocv: expected OCV3/OCV4\n")
  return
end

local screenH = u32be(header, 5)
local screenW = u32be(header, 9)
local fps = u32be(header, 13)
local frameSize = u32be(header, 17)
local frameCount = u32be(header, 21)
local chunkCount = u32be(header, 25)
local framesPerChunk = u32be(header, 29)
local codec = magic == "OCV4" and "delta" or "raw"

print("")
print(string.format("Format: %s (%s)", magic, codec))
print(string.format("Video : %dx%d chars, %d fps", screenW, screenH, fps))
print(string.format("Frames: %d, chunks: %d, frame size: %s, chunk frames: %d", frameCount, chunkCount, formatBytes(frameSize), framesPerChunk))
print("")

for i = 1, chunkCount do
  local name = string.format("part%04d.ocv", i)
  local partOk, partErr = download(baseUrl .. name, fs.concat(outDir, name), name, i + 1, chunkCount + 1)
  if not partOk then
    io.stderr:write("download failed: " .. name .. ": " .. tostring(partErr) .. "\n")
    return
  end
end

print("")
print("Done. Run: player " .. outDir)