prefer-downloads.lua

local mp = require("mp")
local utils = require("mp.utils")

ROOT_URL = "http://localhost:32700"

local char_to_hex = function(c)
  return string.format("%%%02X", string.byte(c))
end

function fetch_json(url)
    local curl_args = {
        "curl",
        "-L",
        "--silent",
        "--max-time", "5",
        "-H", "Accept: application/json",
        url
    }

    local subprocess = mp.command_native {
        name = "subprocess",
        capture_stdout = true,
        playback_only = false,
        args = curl_args
    }

    return utils.parse_json(subprocess.stdout or "") or {}
end

local function urlencode(url)
  if url == nil then
    return
  end
  url = url:gsub("([^%w ])", char_to_hex)
  url = url:gsub(" ", "+")
  return url
end

function on_load(defer, cont)
    local metadataItem = mp.get_property_native("user-data/plex/playing-media/decision/metadataItem")
    local source = metadataItem["source"]
    local guid = metadataItem["guid"]

    if not source or not guid then
        return
    end

    local providers = fetch_json(ROOT_URL .. "/media/providers")
    local provider = nil
    for _, curProvider in ipairs((providers.MediaContainer or {}).MediaProvider or {}) do
        if curProvider["source"] == source then
            provider = curProvider
            break
        end
    end

    if not provider then
        return
    end

    local providerPath = "/media/providers/" .. provider["id"]

    local downloadedMetadataPath = providerPath .. "/library/metadata/" .. urlencode(guid)

    local downloadedMetadata = fetch_json(ROOT_URL .. downloadedMetadataPath)

    if not downloadedMetadata then
        return
    end

    local partKey = (((((((downloadedMetadata.MediaContainer or {}).Metadata or {})[1] or {}).Media or {})[1] or {}).Part or {})[1] or {})["key"]

    if partKey then
        mp.set_property("stream-open-filename", ROOT_URL .. partKey)
    end
end

mp.add_hook("on_load", 30, on_load)