local enet = require("enet")
local socket = require("socket")
local util = require("util")
local common = require("common")
local save_file = require("save_file")

local server = {}

local function migrate_save(save)
    save.players = save.players or {}
end

local function save_data(srv)
    -- TODO: handle failure
    save_file.write(srv.save_file, srv.data)
end

local function get_player(srv, name)
    for _, player in ipairs(srv.data.players) do
        if player.name == name then
            return player
        end
    end
end

local function get_players(srv)
    local players = {}
    for _, player in ipairs(srv.data.players) do
        table.insert(players, {
            name = player.name,
            active = srv.players[player.name] ~= nil,
        })
    end
    return players
end

local function get_info_pkt(srv)
    return util.json_enc({
        type = "client_info",
        players = get_players(srv),
    })
end

local function broadcast_info(srv)
    local pkt = get_info_pkt(srv)
    for _, clt in pairs(srv.clients) do
        clt.peer:send(pkt)
    end
end

local function create_player(srv, name)
    local player = { name = name }
    table.insert(srv.data.players, player)
    print("[server] created player " .. name)
    save_data(srv)
    return player
end

local function disconnect(srv, clt)
    srv.clients[clt.peer] = nil
    if clt.player then
        srv.players[clt.player.name] = nil
    end
    broadcast_info(srv)
end

local function select_player(srv, clt, pkt)
    if #pkt.name > 128 then
        return "name_too_long"
    end
    if srv.players[pkt.name] then
        return nil, "already_active"
    end
    local player = get_player(srv, pkt.name)
    if pkt.create and player then
        return nil, "already_exists"
    end
    if not pkt.create and not player then
        return nil, "not_exists"
    end

    if pkt.create then
        player = create_player(srv, pkt.name)
    end
    return player
end

function server.create(filename, match_addr)
    local srv = {}

    srv.host = enet.host_create()
    srv.secret = util.rand_string(common.secret_len)
    srv.clients = {}
    srv.players = {}

    srv.match = srv.host:connect(match_addr or common.default_match_addr)
    srv.match_req = socket.gettime()

    local save, err = save_file.read(filename)
    if err then
        return nil, err
    end
    srv.save_file = filename
    srv.data = save
    migrate_save(save)

    return srv
end

local function handle_match(srv, pkt)
    if pkt.type == "server_match" then
        local game_id = type(pkt.game_id) == "string" and util.base64_dec(pkt.game_id)
        if not game_id then
            print("[server] server_match: invalid game_id")
            return
        end

        if srv.game_id then
            print("[server] server_match: received while game already running")
            return
        end

        srv.game_id = game_id
        srv.invite = util.base64_enc(srv.game_id .. srv.secret)
    elseif pkt.type == "server_join" then
        if type(pkt.peer_addr) ~= "string" then
            print("[server] server_join: invalid peer_addr")
            return
        end
        srv.host:connect(pkt.peer_addr)
    end
end

local function handle_client(srv, peer, pkt)
    if pkt.type == "server_hi" then
        local secret = type(pkt.secret) == "string" and util.base64_dec(pkt.secret)
        if not secret then
            print("[server] server_hi: invalid secret")
            return
        end

        if srv.clients[peer] then
            print("[server] server_hi: client already connected")
            return
        end

        if secret == srv.secret then
            print("[server] auth success " .. tostring(peer))
            local clt = { peer = peer }
            srv.clients[peer] = clt
            util.send(peer, {
                type = "client_hi",
            })
            peer:send(get_info_pkt(srv))
        else
            print("[server] auth failure " .. tostring(peer))
            util.send(peer, { type = "client_reject" })
            peer:disconnect_later()
       end
    end

    local clt = srv.clients[peer]
    if not clt then
        print("[server] dropping unauthenicated packet from " .. tostring(peer))
        return
    end

    if pkt.type == "server_player" then
        if clt.player then
            print("[server] dropping server_player from already authenticated player")
            return
        end

        if type(pkt.name) ~= "string" or type(pkt.create) ~= "boolean" then
            print("[server] server_player: invalid packet")
            return
        end

        local player, err = select_player(srv, clt, pkt)
        if err then
            print("[server] failed to select player " .. tostring(clt.peer))
            util.send(clt.peer, {
                type = "client_player_fail",
                error = err,
            })
        else
            print("[server] select player " .. tostring(clt.peer) .. ": " .. player.name)
            srv.players[player.name] = clt
            clt.player = player
            util.send(clt.peer, {
                type = "client_player",
                name = player.name,
            })
            broadcast_info(srv)
        end
    end
end

function server.update(srv)
    local event = srv.host:service(20)
    while event do
        if event.type == "receive" then
            local pkt = util.json_dec(event.data)
            if pkt then
                if event.peer == srv.match then
                    handle_match(srv, pkt)
                else
                    handle_client(srv, event.peer, pkt)
                end
            end
        elseif event.type == "connect" then
            if event.peer == srv.match then
                util.send(srv.match, { type = "match_register" })
            end
            print("[server] connect " .. tostring(event.peer))
        elseif event.type == "disconnect" then
            print("[server] disconnect " .. tostring(event.peer))
            if event.peer == srv.match then
                -- TODO
            else
                local clt = srv.clients[event.peer]
                if clt then
                    disconnect(srv, clt)
                end
            end
        end
        event = srv.host:service()
    end
end

function server.match_status(srv)
    if srv.game_id then
        return "active", srv.invite
    elseif srv.match_req + 3 >= socket.gettime() then
        return "wait"
    else
        return "fail"
    end
end

function server.close(srv)
    save_data(srv)
    local peers = srv.host:peer_count()
    for i = 1, peers do
        srv.host:get_peer(i):disconnect()
    end
    srv.host:flush()
    srv.host:destroy()
end

return server