// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

library fuchsia.logger;

using zx;

enum LogLevelFilter : int8 {
    NONE = -1;
    INFO = 0;
    WARN = 1;
    ERROR = 2;
    FATAL = 3;
};

/// Max number of tags that can be passed to filter by listener.
const uint8 MAX_TAGS = 5;

/// Max tag length that can be passed to filter by listener.
const uint8 MAX_TAG_LEN_BYTES = 63;

struct LogFilterOptions {
    bool filter_by_pid;
    uint64 pid;

    bool filter_by_tid;
    uint64 tid;

    /// If more than zero, logs would be filtered based on verbosity and
    /// `min_severity` would be ignored.
    uint8 verbosity;

    LogLevelFilter min_severity;

    /// If non-empty, return all messages which contain at least one specified
    /// tag.  If empty, messages will not be filtered by tag.
    /// Passed tags should not be more than `MAX_TAG_LEN_BYTES` bytes in length
    /// and max tags can be `MAX_TAGS`.
    /// Listener would be discarded if the limit is not followed.
    vector<string:MAX_TAG_LEN_BYTES>:MAX_TAGS tags;
};

/// Max tags that will be attached to a LogMessage.
const uint8 MAX_TAGS_PER_LOG_MESSAGE = 5;

/// Max byte size for message payload.
const uint32 MAX_DATAGRAM_LEN_BYTES = 2032;

struct LogMessage {
    uint64 pid;
    uint64 tid;
    /// https://fuchsia.dev/fuchsia-src/reference/syscalls/clock_get_monotonic.md
    zx.time time;
    int32 severity;

    /// See //zircon/system/ulib/syslog/include/syslog/wire_format.h. As messages
    /// can be served out of order, this should only be logged if more than last
    /// count.
    uint32 dropped_logs;
    vector<string:MAX_TAG_LEN_BYTES>:MAX_TAGS_PER_LOG_MESSAGE tags;
    string:MAX_DATAGRAM_LEN_BYTES msg;
};

/// Interface for LogListenerSafe to register to listen to logs.
[Discoverable]
protocol Log {
    [Deprecated]
    Listen(LogListener log_listener, LogFilterOptions? options);

    [Deprecated]
    DumpLogs(LogListener log_listener, LogFilterOptions? options);

    /// Listens to new log entries by calling Log() on `log_listener`. A null `options` indicates no
    /// filtering is requested.
    [Transitional]
    ListenSafe(LogListenerSafe log_listener, LogFilterOptions? options);

    /// Dumps all cached logs by calling LogMany() followed by Done() on `log_listener`.
    /// A null `options` indicates no filtering is requested.
    [Transitional]
    DumpLogsSafe(LogListenerSafe log_listener, LogFilterOptions? options);
};

/// Drains a program's logs.
[Discoverable]
protocol LogSink {
    /// Send this socket to be drained.
    ///
    /// See //zircon/system/ulib/syslog/include/syslog/wire_format.h for what is expected to be
    /// received over the socket.
    Connect(handle<socket> socket);
};

/// Max log bytes per call to a listener.
const uint64 MAX_LOG_MANY_SIZE_BYTES = 16384;

/// Included temporarily for backwards compatiblity. Use `LogListenerSafe`.
[Deprecated]
protocol LogListener {
    Log(LogMessage log);
    LogMany(vector<LogMessage>:MAX log);
    Done();
};

/// A listener who will notify the `Log` of the receipt of each message.
protocol LogListenerSafe {
    /// Called for single messages.
    ///
    /// The return value is used for flow control, and implementers should acknowledge receipt of
    /// each message in order to continue receiving future messages.
    Log(LogMessage log) -> ();

    /// Called when serving cached logs.
    ///
    /// Max logs size per call is `MAX_LOG_MANY_SIZE_BYTES` bytes.
    ///
    /// The return value is used for flow control, and implementers should acknowledge receipt of
    /// each batch in order to continue receiving future messages.
    LogMany(vector<LogMessage>:MAX log) -> ();

    /// Called when this listener was passed to `DumpLogsSafe()` and all cached logs have been sent.
    Done();
};