local component = require("component")
local fs = require("filesystem")
local internet = require("internet")
local shell = require("shell")
local text = require("text")

if not component.isAvailable("internet") then
  io.stderr:write("This program requires an internet card to run.")
  return
end

local args, options = shell.parse(...)
options.q = options.q or options.Q

if #args < 1 then
  io.write("Usage: wget [-fq] <url> [<filename>]\n")
  io.write(" -f: Force overwriting existing files.\n")
  io.write(" -q: Quiet mode - no status messages.\n")
  io.write(" -Q: Superquiet mode - no error messages.")
  return
end

local url = text.trim(args[1])
local filename = args[2]
if not filename then
  filename = url
  local index = string.find(filename, "/[^/]*$")
  if index then
    filename = string.sub(filename, index + 1)
  end
  index = string.find(filename, "?", 1, true)
  if index then
    filename = string.sub(filename, 1, index - 1)
  end
end
filename = text.trim(filename)
if filename == "" then
  if not options.Q then
    io.stderr:write("could not infer filename, please specify one")
  end
  return nil, "missing target filename" -- for programs using wget as a function
end
filename = shell.resolve(filename)

local preexisted
if fs.exists(filename) then
  preexisted = true
  if not options.f then
    if not options.Q then
      io.stderr:write("file already exists")
    end
    return nil, "file already exists" -- for programs using wget as a function
  end
end

local f, reason = io.open(filename, "a")
if not f then
  if not options.Q then
    io.stderr:write("failed opening file for writing: " .. reason)
  end
  return nil, "failed opening file for writing: " .. reason -- for programs using wget as a function
end
f:close()
f = nil

if not options.q then
  io.write("Downloading... ")
end
local result, response = pcall(internet.request, url, nil, {["user-agent"]="Wget/OpenComputers"})
if result then
  local result, reason = pcall(function()
    for chunk in response do
      if not f then
        f, reason = io.open(filename, "wb")
        assert(f, "failed opening file for writing: " .. tostring(reason))
      end
      f:write(chunk)
    end
  end)
  if not result then
    if not options.q then
      io.stderr:write("failed.\n")
    end
    if f then
      f:close()
      if not preexisted then
        fs.remove(filename)
      end
    end
    if not options.Q then
      io.stderr:write("HTTP request failed: " .. reason .. "\n")
    end
    return nil, reason -- for programs using wget as a function
  end
  if not options.q then
    io.write("success.\n")
  end

  if f then
    f:close()
  end

  if not options.q then
    io.write("Saved data to " .. filename .. "\n")
  end
else
  if not options.q then
    io.write("failed.\n")
  end
  if not options.Q then
    io.stderr:write("HTTP request failed: " .. response .. "\n")
  end
  return nil, response -- for programs using wget as a function
end
return true -- for programs using wget as a function