local vim = vim
local uv = vim.loop

local F = require "plenary.functional"

---@class Job
---@field command string          : Command to run
---@field args Array              : List of arguments to pass
---@field cwd string              : Working directory for job
---@field env Map|Array           : Environment looking like: { ['VAR'] = 'VALUE } or { 'VAR=VALUE' }
---@field skip_validation boolean : Skip validating the arguments
---@field enable_handlers boolean : If set to false, disables all callbacks associated with output
---@field on_start function       : Run when starting job
---@field on_stdout function      : (error: string, data: string, self? Job)
---@field on_stderr function      : (error: string, data: string, self? Job)
---@field on_exit function        : (self, code: number, signal: number)
---@field maximum_results number  : stop processing results after this number
---@field writer Job|table|string : Job that writes to stdin of this job.
---@field detached boolean        : Spawn the child in a detached state making it a process group leader
---@field enabled_recording boolean
local Job = {}
Job.__index = Job

local function close_safely(j, key)
  local handle = j[key]

  if not handle then
    return
  end

  if not handle:is_closing() then
    handle:close()
  end
end

local start_shutdown_check = function(child, options, code, signal)
  uv.check_start(child._shutdown_check, function()
    if not child:_pipes_are_closed(options) then
      return
    end

    -- Wait until all the pipes are closing.
    uv.check_stop(child._shutdown_check)
    child._shutdown_check = nil

    child:_shutdown(code, signal)

    -- Remove left over references
    child = nil
  end)
end

local shutdown_factory = function(child, options)
  return function(code, signal)
    if uv.is_closing(child._shutdown_check) then
      return child:shutdown(code, signal)
    else
      start_shutdown_check(child, options, code, signal)
    end
  end
end

local function expand(path)
  if vim.in_fast_event() then
    return assert(uv.fs_realpath(path), string.format("Path must be valid: %s", path))
  else
    -- TODO: Probably want to check that this is valid here... otherwise that's weird.
    return vim.fn.expand(path, true)
  end
end

---@class Array
--- Numeric table

---@class Map
--- Map-like table

---Create a new job
---@param o Job
---@return Job
function Job:new(o)
  if not o then
    error(debug.traceback "Options are required for Job:new")
  end

  local command = o.command
  if not command then
    if o[1] then
      command = o[1]
    else
      error(debug.traceback "'command' is required for Job:new")
    end
  elseif o[1] then
    error(debug.traceback "Cannot pass both 'command' and array args")
  end

  local args = o.args
  if not args then
    if #o > 1 then
      args = { select(2, unpack(o)) }
    end
  end

  local ok, is_exe = pcall(vim.fn.executable, command)
  if not o.skip_validation and ok and 1 ~= is_exe then
    error(debug.traceback(command .. ": Executable not found"))
  end

  local obj = {}

  obj.command = command
  obj.args = args
  obj._raw_cwd = o.cwd
  if o.env then
    if type(o.env) ~= "table" then
      error "[plenary.job] env has to be a table"
    end

    local transform = {}
    for k, v in pairs(o.env) do
      if type(k) == "number" then
        table.insert(transform, v)
      elseif type(k) == "string" then
        table.insert(transform, k .. "=" .. tostring(v))
      end
    end
    obj.env = transform
  end
  if o.interactive == nil then
    obj.interactive = true
  else
    obj.interactive = o.interactive
  end

  if o.detached then
    obj.detached = true
  end

  -- enable_handlers: Do you want to do ANYTHING with the stdout/stderr of the proc
  obj.enable_handlers = F.if_nil(o.enable_handlers, true, o.enable_handlers)

  -- enable_recording: Do you want to record stdout/stderr into a table.
  --                    Since it cannot be enabled when enable_handlers is false,
  --                    we try and make sure they are associated correctly.
  obj.enable_recording = F.if_nil(
    F.if_nil(o.enable_recording, o.enable_handlers, o.enable_recording),
    true,
    o.enable_recording
  )

  if not obj.enable_handlers and obj.enable_recording then
    error "[plenary.job] Cannot record items but disable handlers"
  end

  obj._user_on_start = o.on_start
  obj._user_on_stdout = o.on_stdout
  obj._user_on_stderr = o.on_stderr
  obj._user_on_exit = o.on_exit

  obj._additional_on_exit_callbacks = {}

  obj._maximum_results = o.maximum_results

  obj.user_data = {}

  obj.writer = o.writer

  self._reset(obj)

  return setmetatable(obj, self)
end

function Job:_reset()
  self.is_shutdown = nil

  if self._shutdown_check and uv.is_active(self._shutdown_check) and not uv.is_closing(self._shutdown_check) then
    vim.api.nvim_err_writeln(debug.traceback "We may be memory leaking here. Please report to TJ.")
  end
  self._shutdown_check = uv.new_check()

  self.stdin = nil
  self.stdout = nil
  self.stderr = nil

  self._stdout_reader = nil
  self._stderr_reader = nil

  if self.enable_recording then
    self._stdout_results = {}
    self._stderr_results = {}
  else
    self._stdout_results = nil
    self._stderr_results = nil
  end
end

--- Stop a job and close all handles
function Job:_stop()
  close_safely(self, "stdin")
  close_safely(self, "stderr")
  close_safely(self, "stdout")
  close_safely(self, "handle")
end

function Job:_pipes_are_closed(options)
  for _, pipe in ipairs { options.stdin, options.stdout, options.stderr } do
    if pipe and not uv.is_closing(pipe) then
      return false
    end
  end

  return true
end

--- Shutdown a job.
function Job:shutdown(code, signal)
  if self._shutdown_check and not uv.is_active(self._shutdown_check) then
    vim.wait(1000, function()
      return self:_pipes_are_closed(self) and self.is_shutdown
    end, 1, true)
  end

  self:_shutdown(code, signal)
end

function Job:_shutdown(code, signal)
  if self.is_shutdown then
    return
  end

  self.code = code
  self.signal = signal

  if self._stdout_reader then
    pcall(self._stdout_reader, nil, nil, true)
  end

  if self._stderr_reader then
    pcall(self._stderr_reader, nil, nil, true)
  end

  if self._user_on_exit then
    self:_user_on_exit(code, signal)
  end

  for _, v in ipairs(self._additional_on_exit_callbacks) do
    v(self, code, signal)
  end

  if self.stdout then
    self.stdout:read_stop()
  end

  if self.stderr then
    self.stderr:read_stop()
  end

  self:_stop()

  self.is_shutdown = true

  self._stdout_reader = nil
  self._stderr_reader = nil
end

function Job:_create_uv_options()
  local options = {}

  options.command = self.command
  options.args = self.args
  options.stdio = { self.stdin, self.stdout, self.stderr }

  if self._raw_cwd then
    options.cwd = expand(self._raw_cwd)
  end
  if self.env then
    options.env = self.env
  end

  if self.detached then
    options.detached = true
  end

  return options
end

local on_output = function(self, result_key, cb)
  return coroutine.wrap(function(err, data, is_complete)
    local result_index = 1

    local line, start, result_line, found_newline

    -- We repeat forever as a coroutine so that we can keep calling this.
    while true do
      if data then
        data = data:gsub("\r", "")

        local processed_index = 1
        local data_length = #data + 1

        repeat
          start = string.find(data, "\n", processed_index, true) or data_length
          line = string.sub(data, processed_index, start - 1)
          found_newline = start ~= data_length

          -- Concat to last line if there was something there already.
          --    This happens when "data" is broken into chunks and sometimes
          --    the content is sent without any newlines.
          if result_line then
            -- results[result_index] = results[result_index] .. line
            result_line = result_line .. line

            -- Only put in a new line when we actually have new data to split.
            --    This is generally only false when we do end with a new line.
            --    It prevents putting in a "" to the end of the results.
          elseif start ~= processed_index or found_newline then
            -- results[result_index] = line
            result_line = line

            -- Otherwise, we don't need to do anything.
          end

          if found_newline then
            if not result_line then
              return vim.api.nvim_err_writeln(
                "Broken data thing due to: " .. tostring(result_line) .. " " .. tostring(data)
              )
            end

            if self.enable_recording then
              self[result_key][result_index] = result_line
            end

            if cb then
              cb(err, result_line, self)
            end

            -- Stop processing if we've surpassed the maximum.
            if self._maximum_results and result_index > self._maximum_results then
              -- Shutdown once we get the chance.
              --  Can't call it here, because we'll just keep calling ourselves.
              vim.schedule(function()
                self:shutdown()
              end)

              return
            end

            result_index = result_index + 1
            result_line = nil
          end

          processed_index = start + 1
        until not found_newline
      end

      if self.enable_recording then
        self[result_key][result_index] = result_line
      end

      -- If we didn't get a newline on the last execute, send the final results.
      if cb and is_complete and not found_newline then
        cb(err, result_line, self)
      end

      if data == nil or is_complete then
        return
      end

      err, data, is_complete = coroutine.yield()
    end
  end)
end

--- Stop previous execution and add new pipes.
--- Also regenerates pipes of writer.
function Job:_prepare_pipes()
  self:_stop()

  if self.writer then
    if Job.is_job(self.writer) then
      self.writer:_prepare_pipes()
      self.stdin = self.writer.stdout
    elseif self.writer.write then
      self.stdin = self.writer
    end
  end

  if not self.stdin then
    self.stdin = self.interactive and uv.new_pipe(false) or nil
  end

  self.stdout = uv.new_pipe(false)
  self.stderr = uv.new_pipe(false)
end

--- Execute job. Should be called only after preprocessing is done.
function Job:_execute()
  local options = self:_create_uv_options()

  if self._user_on_start then
    self:_user_on_start()
  end

  self.handle, self.pid = uv.spawn(options.command, options, shutdown_factory(self, options))

  if not self.handle then
    error(debug.traceback("Failed to spawn process: " .. vim.inspect(self)))
  end

  if self.enable_handlers then
    self._stdout_reader = on_output(self, "_stdout_results", self._user_on_stdout)
    self.stdout:read_start(self._stdout_reader)

    self._stderr_reader = on_output(self, "_stderr_results", self._user_on_stderr)
    self.stderr:read_start(self._stderr_reader)
  end

  if self.writer then
    if Job.is_job(self.writer) then
      self.writer:_execute()
    elseif type(self.writer) == "table" and vim.tbl_islist(self.writer) then
      local writer_len = #self.writer
      for i, v in ipairs(self.writer) do
        self.stdin:write(v)
        if i ~= writer_len then
          self.stdin:write "\n"
        else
          self.stdin:write("\n", function()
            pcall(self.stdin.close, self.stdin)
          end)
        end
      end
    elseif type(self.writer) == "string" then
      self.stdin:write(self.writer, function()
        self.stdin:close()
      end)
    elseif self.writer.write then
      self.stdin = self.writer
    else
      error("Unknown self.writer: " .. vim.inspect(self.writer))
    end
  end

  return self
end

function Job:start()
  self:_reset()
  self:_prepare_pipes()
  self:_execute()
end

function Job:sync(timeout, wait_interval)
  self:start()
  self:wait(timeout, wait_interval)

  return self.enable_recording and self:result() or nil, self.code
end

function Job:result()
  assert(self.enable_recording, "'enabled_recording' is not enabled for this job.")
  return self._stdout_results
end

function Job:stderr_result()
  assert(self.enable_recording, "'enabled_recording' is not enabled for this job.")
  return self._stderr_results
end

function Job:pid()
  return self.pid
end

function Job:wait(timeout, wait_interval, should_redraw)
  timeout = timeout or 5000
  wait_interval = wait_interval or 10

  if self.handle == nil then
    local msg = vim.inspect(self)
    vim.schedule(function()
      vim.api.nvim_err_writeln(msg)
    end)

    return
  end

  -- Wait five seconds, or until timeout.
  local wait_result = vim.wait(timeout, function()
    if should_redraw then
      vim.cmd [[redraw!]]
    end

    if self.is_shutdown then
      assert(not self.handle or self.handle:is_closing(), "Job must be shutdown if it's closing")
    end

    return self.is_shutdown
  end, wait_interval, not should_redraw)

  if not wait_result then
    error(
      string.format(
        "'%s %s' was unable to complete in %s ms",
        self.command,
        table.concat(self.args or {}, " "),
        timeout
      )
    )
  end

  return self
end

function Job:co_wait(wait_time)
  wait_time = wait_time or 5

  if self.handle == nil then
    vim.api.nvim_err_writeln(vim.inspect(self))
    return
  end

  while not vim.wait(wait_time, function()
    return self.is_shutdown
  end) do
    coroutine.yield()
  end

  return self
end

--- Wait for all jobs to complete
function Job.join(...)
  local jobs_to_wait = { ... }
  local num_jobs = table.getn(jobs_to_wait)

  -- last entry can be timeout
  local timeout
  if type(jobs_to_wait[num_jobs]) == "number" then
    timeout = table.remove(jobs_to_wait, num_jobs)
    num_jobs = num_jobs - 1
  end

  local completed = 0

  return vim.wait(timeout or 10000, function()
    for index, current_job in pairs(jobs_to_wait) do
      if current_job.is_shutdown then
        jobs_to_wait[index] = nil
        completed = completed + 1
      end
    end

    return num_jobs == completed
  end)
end

local _request_id = 0
local _request_status = {}

function Job:and_then(next_job)
  self:add_on_exit_callback(function()
    next_job:start()
  end)
end

function Job:and_then_wrap(next_job)
  self:add_on_exit_callback(vim.schedule_wrap(function()
    next_job:start()
  end))
end

function Job:after(fn)
  self:add_on_exit_callback(fn)
  return self
end

function Job:and_then_on_success(next_job)
  self:add_on_exit_callback(function(_, code)
    if code == 0 then
      next_job:start()
    end
  end)
end

function Job:and_then_on_success_wrap(next_job)
  self:add_on_exit_callback(vim.schedule_wrap(function(_, code)
    if code == 0 then
      next_job:start()
    end
  end))
end

function Job:after_success(fn)
  self:add_on_exit_callback(function(j, code, signal)
    if code == 0 then
      fn(j, code, signal)
    end
  end)
end

function Job:and_then_on_failure(next_job)
  self:add_on_exit_callback(function(_, code)
    if code ~= 0 then
      next_job:start()
    end
  end)
end

function Job:and_then_on_failure_wrap(next_job)
  self:add_on_exit_callback(vim.schedule_wrap(function(_, code)
    if code ~= 0 then
      next_job:start()
    end
  end))
end

function Job:after_failure(fn)
  self:add_on_exit_callback(function(j, code, signal)
    if code ~= 0 then
      fn(j, code, signal)
    end
  end)
end

function Job.chain(...)
  _request_id = _request_id + 1
  _request_status[_request_id] = false

  local jobs = { ... }

  for index = 2, #jobs do
    local prev_job = jobs[index - 1]
    local job = jobs[index]

    prev_job:add_on_exit_callback(vim.schedule_wrap(function()
      job:start()
    end))
  end

  local last_on_exit = jobs[#jobs]._user_on_exit
  jobs[#jobs]._user_on_exit = function(self, err, data)
    if last_on_exit then
      last_on_exit(self, err, data)
    end

    _request_status[_request_id] = true
  end

  jobs[1]:start()

  return _request_id
end

function Job.chain_status(id)
  return _request_status[id]
end

function Job.is_job(item)
  if type(item) ~= "table" then
    return false
  end

  return getmetatable(item) == Job
end

function Job:add_on_exit_callback(cb)
  table.insert(self._additional_on_exit_callbacks, cb)
end

--- Send data to a job.
function Job:send(data)
  if not self.stdin then
    error "job has no 'stdin'. Have you run `job:start()` yet?"
  end

  self.stdin:write(data)
end

return Job