local socket = require "socket";
local ssl = require "ssl";
local b64 = require "prosody.util.encodings".base64.encode;

local smtp_server = module:get_option_string("offline_email_smtp_server");
local smtp_port = module:get_option_number("offline_email_smtp_port", 587);
local smtp_username = module:get_option_string("offline_email_smtp_username");
local smtp_password = module:get_option_string("offline_email_smtp_password");
local smtp_from = module:get_option_string("offline_email_smtp_from", smtp_username);

local accounts = module:open_store("accounts");

local function read_response(sock)
    local lines = {};
    while true do
        local line, err = sock:receive("*l");
        if not line then return nil, err; end
        table.insert(lines, line);
        if line:sub(4, 4) == " " then break; end
    end
    local code = tonumber(lines[1]:sub(1, 3));
    return code, table.concat(lines, "\n");
end

local function send_command(sock, cmd)
    sock:send(cmd .. "\r\n");
    return read_response(sock);
end

local function send_email(to_email, subject, body_text)
    local sock = socket.tcp();
    sock:settimeout(10);

    local ok, err = sock:connect(smtp_server, smtp_port);
    if not ok then return nil, "connect: " .. tostring(err); end

    local code, resp = read_response(sock);
    if not code or code ~= 220 then
        sock:close();
        return nil, "greeting: " .. tostring(resp);
    end

    code = send_command(sock, "EHLO localhost");
    if code ~= 250 then sock:close(); return nil, "EHLO failed"; end

    code = send_command(sock, "STARTTLS");
    if code ~= 220 then sock:close(); return nil, "STARTTLS rejected"; end

    sock = ssl.wrap(sock, { mode = "client", protocol = "any", verify = "none" });
    ok = sock:dohandshake();
    if not ok then sock:close(); return nil, "TLS handshake failed"; end

    code = send_command(sock, "EHLO localhost");
    if code ~= 250 then sock:close(); return nil, "EHLO after TLS failed"; end

    local auth_str = b64("\0" .. smtp_username .. "\0" .. smtp_password);
    code = send_command(sock, "AUTH PLAIN " .. auth_str);
    if code ~= 235 then sock:close(); return nil, "AUTH failed"; end

    code = send_command(sock, "MAIL FROM:<" .. smtp_from .. ">");
    if code ~= 250 then sock:close(); return nil, "MAIL FROM failed"; end

    code = send_command(sock, "RCPT TO:<" .. to_email .. ">");
    if code ~= 250 then sock:close(); return nil, "RCPT TO failed"; end

    code = send_command(sock, "DATA");
    if code ~= 354 then sock:close(); return nil, "DATA failed"; end

    local message = "From: " .. smtp_from .. "\r\n" ..
        "To: " .. to_email .. "\r\n" ..
        "Subject: " .. subject .. "\r\n" ..
        "Content-Type: text/plain; charset=UTF-8\r\n" ..
        "\r\n" ..
        body_text .. "\r\n.\r\n";
    sock:send(message);
    code = read_response(sock);
    if code ~= 250 then sock:close(); return nil, "message rejected"; end

    send_command(sock, "QUIT");
    sock:close();
    return true;
end

local function notify_offline(to_user, stanza)
    local body = stanza:get_child_text("body");
    local is_encrypted = stanza:get_child("encrypted", "eu.siacs.conversations.axolotl") ~= nil;

    if not is_encrypted and (not body or body == "") then return; end

    local account = accounts:get(to_user);
    if not account or not account.email then return; end

    local from_jid = stanza.attr.from or "unknown";
    local from_name = from_jid:match("^([^@]+)") or from_jid;
    local subject = "New message from " .. from_name;
    local email_body;
    if is_encrypted then
        email_body = "Ahoy,\r\n\r\n" ..
            "while offline, you've received an encrypted message from " .. from_name .. ".\r\n\r\n" ..
            "This message was sent using end-to-end encryption (OMEMO).\r\n" ..
            "To view it, log in from the same device where your encryption keys are stored. " ..
            "The message cannot be read on a different device or client.\r\n\r\n" ..
            "Kind regards,\r\n\r\n" ..
            "Tiara";
    else
        email_body = "Ahoy,\r\n\r\n" ..
            "while offline, you received a plain-text message from " .. from_name .. ":\r\n\r\n" ..
            ">> " .. body .. "\r\n\r\n" ..
            "Kind regards,\r\n\r\n" ..
            "Tiara";
    end

    local ok, err = send_email(account.email, subject, email_body);
    if ok then
        module:log("info", "Sent offline email notification to %s for user %s", account.email, to_user);
    else
        module:log("warn", "Failed to send offline email to %s: %s", account.email, tostring(err));
    end
end

local bare_sessions = prosody.bare_sessions;
local jid = require "util.jid";

local function has_hibernating_session(username)
    local bare = username .. "@" .. module.host;
    local user = bare_sessions[bare];
    if not user then return false; end
    for _, session in pairs(user.sessions) do
        if session.hibernating then return true; end
    end
    return false;
end

-- Fired when user is offline (no sessions) or when smacks gives up on a hibernating session
module:hook("message/offline/handle", function(event)
    local to_user = event.username or (event.stanza.attr.to and event.stanza.attr.to:match("^([^@]+)"));
    if not to_user then return; end
    -- Skip if smacks is still hibernating — we'll get called again when it expires
    if has_hibernating_session(to_user) then
        module:log("debug", "Skipping email for %s — smacks session still hibernating", to_user);
        return;
    end
    notify_offline(to_user, event.stanza);
end, 1);