msg = require('mp.msg')
msg.trace('sane-sysvol: load: begin')

non_blocking_popen = require("non_blocking_popen")

RD_SIZE = 4096

function startswith(superstring, substring)
  return superstring:sub(1, substring:len()) == substring
end
function strip_prefix(superstring, substring)
  return superstring:sub(substring:len())
end

function ltrim(s)
  -- remove all leading whitespace from `s`
  local i = 1
  while s:sub(i, i) == " " or s:sub(i, i) == "\t" do
    i = i + 1
  end
  return s:sub(i)
end

function subprocess(args)
  mp.command_native({
    name = "subprocess",
    args = args,
    -- these arguments below probably don't matter: copied from sane-cast
    detach = false,
    capture_stdout = false,
    capture_stderr = false,
    passthrough_stdin = false,
    playback_only = false,
  })
end

function sysvol_new()
  return {
    -- sysvol is pipewire-native volume
    -- it's the cube of the equivalent 0-100% value represented inside mpv
    sysvol = nil,
    change_sysvol = function(self, mpv_vol)
      -- called when mpv wants to set the system-wide volume
      if mpv_vol == nil then
        return
      end

      local old_mpv_vol = nil
      if self.sysvol ~= nil then
        old_mpv_vol = 100 * self.sysvol^(1/3)
      end
      if old_mpv_vol ~= nil and math.floor(old_mpv_vol) == math.floor(mpv_vol) then
        return
      end

      local volstr = tostring(mpv_vol) .. "%"
      msg.debug("setting system-wide volume:", volstr)
      self.sysvol = (0.01*mpv_vol)^3
      subprocess({
        "wpctl",
        "set-volume",
        "@DEFAULT_AUDIO_SINK@",
        volstr
      })
    end,
    on_sysvol_change = function(self, sysvol)
      if sysvol == nil then
        return
      end
      -- called when the pipewire system volume is changed (either by us, or an external application)
      local new_mpv_vol = 100 * sysvol^(1/3)
      local old_mpv_vol = nil
      if self.sysvol ~= nil then
        old_mpv_vol = 100 * self.sysvol^(1/3)
      end

      if old_mpv_vol ~= nil and math.abs(new_mpv_vol - old_mpv_vol) < 1.0 then
        msg.debug("NOT announcing volume change to mpv (because it was what triggered the change):", old_mpv_vol, new_mpv_vol)
        return
      end

      self.sysvol = sysvol
      msg.debug("announcing volume change to mpv:", old_mpv_vol, new_mpv_vol)
      mp.set_property_native("user-data/sane-sysvol/volume", new_mpv_vol)
    end
  }
end

function pwmon_parser_new()
  return {
    -- volume: pipewire-native volume. usually 0.0 - 1.0, but can go higher (e.g. 3.25)
    -- `wpctl get-volume` and this volume are related, in that the volume reported by
    -- wpctl is the cube-root of this one.
    volume = {}, -- object-id (number) -> volume (number)
    mute = {}, -- object-id (number) -> mute (bool)
    last_audio_device_id = nil, -- TODO: might not actually be necessary

    -- parser state:
    in_changed = false,
    changed_id = nil,
    in_device = false,
    in_direction = false,
    in_output = false,
    in_vol = false,
    in_mute = false,

    feed_line = function(self, line)
      line = ltrim(line)
      if startswith(line, "changed:") then
        self.in_changed = true
        self.changed_id = nil
        self.in_device = false
        self.in_direction = false
        self.in_output = false
        self.in_vol = false
        self.in_mute = false
        self.in_properties = false
      elseif startswith(line, "added:") or startswith(line, "removed:") then
        self.in_changed = false
        self.changed_id = nil
        self.in_device = false
        self.in_direction = false
        self.in_output = false
        self.in_vol = false
        self.in_mute = false
        self.in_properties = false
      elseif startswith(line, "id: ") and self.in_changed then
        if self.changed_id == nil then
          self.changed_id = tonumber(strip_prefix(line, "id: "))
          msg.debug("changed_id:", self.changed_id)
        end
      elseif startswith(line, "type: ") and self.in_changed then
        self.in_device = startswith(line, "type: PipeWire:Interface:Device")
        msg.trace("parsed type:", line, self.in_device)
      elseif startswith(line, "Prop: ") and self.in_changed and self.in_device then
        self.in_direction = startswith(line, "Prop: key Spa:Pod:Object:Param:Route:direction")
        if self.in_direction then
          self.in_output = false
        end
        -- which of the *Volumes params we read is unclear.
        -- alternative to this is to just detect the change, and then cal wpctl get-volume @DEFAULT_AUDIO_SINK@
        self.in_vol = startswith(line, "Prop: key Spa:Pod:Object:Param:Props:channelVolumes")
        self.in_mute = startswith(line, "Prop: key Spa:Pod:Object:Param:Props:softMute")
        msg.trace("parsed `Prop:`", line, self.in_vol)
      elseif line:find("Spa:Enum:Direction:Output", 1, true) and self.in_direction then
        self.in_output = true
      elseif startswith(line, "Float ") and self.in_changed and self.in_device and self.in_output and self.in_vol then
        value = tonumber(strip_prefix(line, "Float "))
        self:feed_volume(value)
      elseif startswith(line, "Bool ") and self.in_changed and self.in_device and self.in_output and self.in_mute then
        value = tonumber(strip_prefix(line, "Bool ")) == "true"
        self:feed_mute(value)
      elseif startswith(line, "properties:") and self.in_changed and self.in_device then
        self.in_properties = true
      elseif line == 'media.class = "Audio/Device"' and self.in_changed and self.in_device and self.in_properties then
        self.last_audio_device_id = self.changed_id
        msg.debug("last_audio_device_id:", self.changed_id)
      end
    end,

    feed_volume = function(self, vol)
      msg.debug("volume:", self.changed_id, vol)
      self.volume[self.changed_id] = vol
    end,
    feed_mute = function(self, mute)
      msg.debug("mute:", self.changed_id, mute)
      self.mute[self.changed_id] = mute
    end,
    get_effective_volume = function(self, id)
      if id == nil then
        id = self.last_audio_device_id
      end

      if self.mute[id] then
        return 0
      else
        return self.volume[id]
      end
    end
  }
end

function pwmon_new()
  return {
    -- non_blocking_popen handle for the pw-mon process
    -- which can be periodically read and parsed to detect volume changes
    handle = non_blocking_popen.non_blocking_popen("pw-mon", RD_SIZE),
    stdout_unparsed = "",
    pwmon_parser = pwmon_parser_new(),
    service = function(self)
      -- do a single non-blocking read, and parse the result
      -- in the *rare* case in which more than RD_SIZE data is ready, we service that remaining data on the next call
      local buf, res = self.handle:read(RD_SIZE)
      if res == "closed" then
        msg.debug("pw-mon unexpectedly closed!")
      end
      if buf ~= nil then
        self.stdout_unparsed = self.stdout_unparsed .. buf
        self:consume_stdout()
      end
    end,
    consume_stdout = function(self)
      local idx_newline, next_newline = 0, 0
      while next_newline ~= nil do
        next_newline = self.stdout_unparsed:find("\n", idx_newline + 1, true)
        if next_newline ~= nil then
          self:ingest_line(self.stdout_unparsed:sub(idx_newline + 1, next_newline - 1))
          idx_newline = next_newline
        end
      end
      self.stdout_unparsed = self.stdout_unparsed:sub(idx_newline + 1)
    end,
    ingest_line = function(self, line)
      msg.trace("pw-mon:", line)
      local old_vol = self.pwmon_parser:get_effective_volume()
      self.pwmon_parser:feed_line(line)
      local new_vol = self.pwmon_parser:get_effective_volume()
      if new_vol ~= old_vol then
        msg.debug("pipewire volume change:", old_vol, new_vol)
        mp.set_property_native("user-data/sane-sysvol/pw-mon-volume", new_vol)
      end
    end
  }
end


mp.set_property_native("user-data/sane-sysvol/volume", 0)

local sysvol = sysvol_new()
mp.observe_property("user-data/sane-sysvol/volume", "native", function(_, val)
  sysvol:change_sysvol(val)
end)
mp.observe_property("user-data/sane-sysvol/pw-mon-volume", "native", function(_, val)
  sysvol:on_sysvol_change(val)
end)

local pwmon = pwmon_new()
mp.register_event('tick', function() pwmon:service() end)

msg.trace("sane-sysvol: load: complete")