// Copyright 2020 Sigma Prime Pty Ltd.
//
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// copy of this software and associated documentation files (the "Software"),
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use std::borrow::Cow;
use std::time::Duration;

use tetsy_libp2p_core::PeerId;

use crate::types::{FastMessageId, GossipsubMessage, MessageId, RawGossipsubMessage};

/// The types of message validation that can be employed by gossipsub.
#[derive(Debug, Clone)]
pub enum ValidationMode {
    /// This is the default setting. This requires the message author to be a valid [`PeerId`] and to
    /// be present as well as the sequence number. All messages must have valid signatures.
    ///
    /// NOTE: This setting will reject messages from nodes using
    /// [`crate::behaviour::MessageAuthenticity::Anonymous`] and all messages that do not have
    /// signatures.
    Strict,
    /// This setting permits messages that have no author, sequence number or signature. If any of
    /// these fields exist in the message these are validated.
    Permissive,
    /// This setting requires the author, sequence number and signature fields of a message to be
    /// empty. Any message that contains these fields is considered invalid.
    Anonymous,
    /// This setting does not check the author, sequence number or signature fields of incoming
    /// messages. If these fields contain data, they are simply ignored.
    ///
    /// NOTE: This setting will consider messages with invalid signatures as valid messages.
    None,
}

/// Configuration parameters that define the performance of the gossipsub network.
#[derive(Clone)]
pub struct GossipsubConfig {
    protocol_id_prefix: Cow<'static, str>,
    history_length: usize,
    history_gossip: usize,
    mesh_n: usize,
    mesh_n_low: usize,
    mesh_n_high: usize,
    retain_scores: usize,
    gossip_lazy: usize,
    gossip_factor: f64,
    heartbeat_initial_delay: Duration,
    heartbeat_interval: Duration,
    fanout_ttl: Duration,
    check_explicit_peers_ticks: u64,
    max_transmit_size: usize,
    duplicate_cache_time: Duration,
    validate_messages: bool,
    validation_mode: ValidationMode,
    message_id_fn: fn(&GossipsubMessage) -> MessageId,
    fast_message_id_fn: Option<fn(&RawGossipsubMessage) -> FastMessageId>,
    allow_self_origin: bool,
    do_px: bool,
    prune_peers: usize,
    prune_backoff: Duration,
    backoff_slack: u32,
    flood_publish: bool,
    graft_flood_threshold: Duration,
    mesh_outbound_min: usize,
    opportunistic_graft_ticks: u64,
    opportunistic_graft_peers: usize,
    gossip_retransimission: u32,
    max_messages_per_rpc: Option<usize>,
    max_ihave_length: usize,
    max_ihave_messages: usize,
    iwant_followup_time: Duration,
    support_floodsub: bool,
    published_message_ids_cache_time: Duration,
}

impl GossipsubConfig {
    // All the getters

    /// The protocol id prefix to negotiate this protocol. The protocol id is of the form
    /// `/<prefix>/<supported-versions>`. As gossipsub supports version 1.0 and 1.1, there are two
    /// protocol id's supported.
    ///
    /// The default prefix is `meshsub`, giving the supported protocol ids: `/meshsub/1.1.0` and `/meshsub/1.0.0`, negotiated in that order.
    pub fn protocol_id_prefix(&self) -> &Cow<'static, str> {
        &self.protocol_id_prefix
    }

    // Overlay network parameters.
    /// Number of heartbeats to keep in the `memcache` (default is 5).
    pub fn history_length(&self) -> usize {
        self.history_length
    }

    /// Number of past heartbeats to gossip about (default is 3).
    pub fn history_gossip(&self) -> usize {
        self.history_gossip
    }

    /// Target number of peers for the mesh network (D in the spec, default is 6).
    pub fn mesh_n(&self) -> usize {
        self.mesh_n
    }

    /// Minimum number of peers in mesh network before adding more (D_lo in the spec, default is 5).
    pub fn mesh_n_low(&self) -> usize {
        self.mesh_n_low
    }

    /// Maximum number of peers in mesh network before removing some (D_high in the spec, default
    /// is 12).
    pub fn mesh_n_high(&self) -> usize {
        self.mesh_n_high
    }

    /// Affects how peers are selected when pruning a mesh due to over subscription.
    ///
    ///  At least `retain_scores` of the retained peers will be high-scoring, while the remainder are
    ///  chosen randomly (D_score in the spec, default is 4).
    pub fn retain_scores(&self) -> usize {
        self.retain_scores
    }

    /// Minimum number of peers to emit gossip to during a heartbeat (D_lazy in the spec,
    /// default is 6).
    pub fn gossip_lazy(&self) -> usize {
        self.gossip_lazy
    }

    /// Affects how many peers we will emit gossip to at each heartbeat.
    ///
    /// We will send gossip to `gossip_factor * (total number of non-mesh peers)`, or
    /// `gossip_lazy`, whichever is greater. The default is 0.25.
    pub fn gossip_factor(&self) -> f64 {
        self.gossip_factor
    }

    /// Initial delay in each heartbeat (default is 5 seconds).
    pub fn heartbeat_initial_delay(&self) -> Duration {
        self.heartbeat_initial_delay
    }

    /// Time between each heartbeat (default is 1 second).
    pub fn heartbeat_interval(&self) -> Duration {
        self.heartbeat_interval
    }

    /// Time to live for fanout peers (default is 60 seconds).
    pub fn fanout_ttl(&self) -> Duration {
        self.fanout_ttl
    }

    /// The number of heartbeat ticks until we recheck the connection to explicit peers and
    /// reconnecting if necessary (default 300).
    pub fn check_explicit_peers_ticks(&self) -> u64 {
        self.check_explicit_peers_ticks
    }

    /// The maximum byte size for each gossipsub RPC (default is 65536 bytes).
    ///
    /// This represents the maximum size of the entire protobuf payload. It must be at least
    /// large enough to support basic control messages. If Peer eXchange is enabled, this
    /// must be large enough to transmit the desired peer information on pruning. It must be at
    /// least 100 bytes. Default is 65536 bytes.
    pub fn max_transmit_size(&self) -> usize {
        self.max_transmit_size
    }

    /// Duplicates are prevented by storing message id's of known messages in an LRU time cache.
    /// This settings sets the time period that messages are stored in the cache. Duplicates can be
    /// received if duplicate messages are sent at a time greater than this setting apart. The
    /// default is 1 minute.
    pub fn duplicate_cache_time(&self) -> Duration {
        self.duplicate_cache_time
    }

    /// When set to `true`, prevents automatic forwarding of all received messages. This setting
    /// allows a user to validate the messages before propagating them to their peers. If set to
    /// true, the user must manually call [`crate::Gossipsub::report_message_validation_result()`]
    /// on the behaviour to forward message once validated (default is `false`).
    /// The default is `false`.
    pub fn validate_messages(&self) -> bool {
        self.validate_messages
    }

    /// Determines the level of validation used when receiving messages. See [`ValidationMode`]
    /// for the available types. The default is ValidationMode::Strict.
    pub fn validation_mode(&self) -> &ValidationMode {
        &self.validation_mode
    }

    /// A user-defined function allowing the user to specify the message id of a gossipsub message.
    /// The default value is to concatenate the source peer id with a sequence number. Setting this
    /// parameter allows the user to address packets arbitrarily. One example is content based
    /// addressing, where this function may be set to `hash(message)`. This would prevent messages
    /// of the same content from being duplicated.
    ///
    /// The function takes a [`GossipsubMessage`] as input and outputs a String to be interpreted as
    /// the message id.
    pub fn message_id(&self, message: &GossipsubMessage) -> MessageId {
        (self.message_id_fn)(message)
    }

    /// A user-defined optional function that computes fast ids from raw messages. This can be used
    /// to avoid possibly expensive transformations from [`RawGossipsubMessage`] to
    /// [`GossipsubMessage`] for duplicates. Two semantically different messages must always
    /// have different fast message ids, but it is allowed that two semantically identical messages
    /// have different fast message ids as long as the message_id_fn produces the same id for them.
    ///
    /// The function takes a [`RawGossipsubMessage`] as input and outputs a String to be
    /// interpreted as the fast message id. Default is None.
    pub fn fast_message_id(&self, message: &RawGossipsubMessage) -> Option<FastMessageId> {
        self.fast_message_id_fn
            .map(|fast_message_id_fn| fast_message_id_fn(message))
    }

    /// By default, gossipsub will reject messages that are sent to us that have the same message
    /// source as we have specified locally. Enabling this, allows these messages and prevents
    /// penalizing the peer that sent us the message. Default is false.
    pub fn allow_self_origin(&self) -> bool {
        self.allow_self_origin
    }

    /// Whether Peer eXchange is enabled; this should be enabled in bootstrappers and other well
    /// connected/trusted nodes. The default is true.
    pub fn do_px(&self) -> bool {
        self.do_px
    }

    /// Controls the number of peers to include in prune Peer eXchange.
    /// When we prune a peer that's eligible for PX (has a good score, etc), we will try to
    /// send them signed peer records for up to `prune_peers` other peers that we
    /// know of. It is recommended that this value is larger than `mesh_n_high` so that the pruned
    /// peer can reliably form a full mesh. The default is typically 16 however until signed
    /// records are spec'd this is disabled and set to 0.
    pub fn prune_peers(&self) -> usize {
        self.prune_peers
    }

    /// Controls the backoff time for pruned peers. This is how long
    /// a peer must wait before attempting to graft into our mesh again after being pruned.
    /// When pruning a peer, we send them our value of `prune_backoff` so they know
    /// the minimum time to wait. Peers running older versions may not send a backoff time,
    /// so if we receive a prune message without one, we will wait at least `prune_backoff`
    /// before attempting to re-graft. The default is one minute.
    pub fn prune_backoff(&self) -> Duration {
        self.prune_backoff
    }

    /// Number of heartbeat slots considered as slack for backoffs. This gurantees that we wait
    /// at least backoff_slack heartbeats after a backoff is over before we try to graft. This
    /// solves problems occuring through high latencies. In particular if
    /// `backoff_slack * heartbeat_interval` is longer than any latencies between processing
    /// prunes on our side and processing prunes on the receiving side this guarantees that we
    /// get not punished for too early grafting. The default is 1.
    pub fn backoff_slack(&self) -> u32 {
        self.backoff_slack
    }

    /// Whether to do flood publishing or not. If enabled newly created messages will always be
    /// sent to all peers that are subscribed to the topic and have a good enough score.
    /// The default is true.
    pub fn flood_publish(&self) -> bool {
        self.flood_publish
    }

    /// If a GRAFT comes before `graft_flood_threshold` has elapsed since the last PRUNE,
    /// then there is an extra score penalty applied to the peer through P7.
    pub fn graft_flood_threshold(&self) -> Duration {
        self.graft_flood_threshold
    }

    /// Minimum number of outbound peers in the mesh network before adding more (D_out in the spec).
    /// This value must be smaller or equal than `mesh_n / 2` and smaller than `mesh_n_low`.
    /// The default is 2.
    pub fn mesh_outbound_min(&self) -> usize {
        self.mesh_outbound_min
    }

    /// Number of heartbeat ticks that specifcy the interval in which opportunistic grafting is
    /// applied. Every `opportunistic_graft_ticks` we will attempt to select some high-scoring mesh
    /// peers to replace lower-scoring ones, if the median score of our mesh peers falls below a
    /// threshold (see https://godoc.org/github.com/libp2p/go-libp2p-pubsub#PeerScoreThresholds).
    /// The default is 60.
    pub fn opportunistic_graft_ticks(&self) -> u64 {
        self.opportunistic_graft_ticks
    }

    /// Controls how many times we will allow a peer to request the same message id through IWANT
    /// gossip before we start ignoring them. This is designed to prevent peers from spamming us
    /// with requests and wasting our resources. The default is 3.
    pub fn gossip_retransimission(&self) -> u32 {
        self.gossip_retransimission
    }

    /// The maximum number of new peers to graft to during opportunistic grafting. The default is 2.
    pub fn opportunistic_graft_peers(&self) -> usize {
        self.opportunistic_graft_peers
    }

    /// The maximum number of messages we will process in a given RPC. If this is unset, there is
    /// no limit. The default is None.
    pub fn max_messages_per_rpc(&self) -> Option<usize> {
        self.max_messages_per_rpc
    }

    /// The maximum number of messages to include in an IHAVE message.
    /// Also controls the maximum number of IHAVE ids we will accept and request with IWANT from a
    /// peer within a heartbeat, to protect from IHAVE floods. You should adjust this value from the
    /// default if your system is pushing more than 5000 messages in GossipSubHistoryGossip
    /// heartbeats; with the defaults this is 1666 messages/s. The default is 5000.
    pub fn max_ihave_length(&self) -> usize {
        self.max_ihave_length
    }

    /// GossipSubMaxIHaveMessages is the maximum number of IHAVE messages to accept from a peer
    /// within a heartbeat.
    pub fn max_ihave_messages(&self) -> usize {
        self.max_ihave_messages
    }

    /// Time to wait for a message requested through IWANT following an IHAVE advertisement.
    /// If the message is not received within this window, a broken promise is declared and
    /// the router may apply behavioural penalties. The default is 3 seconds.
    pub fn iwant_followup_time(&self) -> Duration {
        self.iwant_followup_time
    }

    /// Enable support for flooodsub peers. Default false.
    pub fn support_floodsub(&self) -> bool {
        self.support_floodsub
    }

    /// Published message ids time cache duration. The default is 10 seconds.
    pub fn published_message_ids_cache_time(&self) -> Duration {
        self.published_message_ids_cache_time
    }
}

impl Default for GossipsubConfig {
    fn default() -> Self {
        // use ConfigBuilder to also validate defaults
        GossipsubConfigBuilder::default()
            .build()
            .expect("Default config parameters should be valid parameters")
    }
}

/// The builder struct for constructing a gossipsub configuration.
pub struct GossipsubConfigBuilder {
    config: GossipsubConfig,
}

impl Default for GossipsubConfigBuilder {
    fn default() -> Self {
        GossipsubConfigBuilder {
            config: GossipsubConfig {
                protocol_id_prefix: Cow::Borrowed("meshsub"),
                history_length: 5,
                history_gossip: 3,
                mesh_n: 6,
                mesh_n_low: 5,
                mesh_n_high: 12,
                retain_scores: 4,
                gossip_lazy: 6, // default to mesh_n
                gossip_factor: 0.25,
                heartbeat_initial_delay: Duration::from_secs(5),
                heartbeat_interval: Duration::from_secs(1),
                fanout_ttl: Duration::from_secs(60),
                check_explicit_peers_ticks: 300,
                max_transmit_size: 65536,
                duplicate_cache_time: Duration::from_secs(60),
                validate_messages: false,
                validation_mode: ValidationMode::Strict,
                message_id_fn: |message| {
                    // default message id is: source + sequence number
                    // NOTE: If either the peer_id or source is not provided, we set to 0;
                    let mut source_string = if let Some(peer_id) = message.source.as_ref() {
                        peer_id.to_base58()
                    } else {
                        PeerId::from_bytes(&[0, 1, 0])
                            .expect("Valid peer id")
                            .to_base58()
                    };
                    source_string
                        .push_str(&message.sequence_number.unwrap_or_default().to_string());
                    MessageId::from(source_string)
                },
                fast_message_id_fn: None,
                allow_self_origin: false,
                do_px: false,
                prune_peers: 0, // NOTE: Increasing this currently has little effect until Signed records are implemented.
                prune_backoff: Duration::from_secs(60),
                backoff_slack: 1,
                flood_publish: true,
                graft_flood_threshold: Duration::from_secs(10),
                mesh_outbound_min: 2,
                opportunistic_graft_ticks: 60,
                opportunistic_graft_peers: 2,
                gossip_retransimission: 3,
                max_messages_per_rpc: None,
                max_ihave_length: 5000,
                max_ihave_messages: 10,
                iwant_followup_time: Duration::from_secs(3),
                support_floodsub: false,
                published_message_ids_cache_time: Duration::from_secs(10),
            },
        }
    }
}

impl From<GossipsubConfig> for GossipsubConfigBuilder {
    fn from(config: GossipsubConfig) -> Self {
        GossipsubConfigBuilder { config }
    }
}

impl GossipsubConfigBuilder {
    /// The protocol id to negotiate this protocol (default is `/meshsub/1.0.0`).
    pub fn protocol_id_prefix(&mut self, protocol_id: impl Into<Cow<'static, str>>) -> &mut Self {
        self.config.protocol_id_prefix = protocol_id.into();
        self
    }

    /// Number of heartbeats to keep in the `memcache` (default is 5).
    pub fn history_length(&mut self, history_length: usize) -> &mut Self {
        self.config.history_length = history_length;
        self
    }

    /// Number of past heartbeats to gossip about (default is 3).
    pub fn history_gossip(&mut self, history_gossip: usize) -> &mut Self {
        self.config.history_gossip = history_gossip;
        self
    }

    /// Target number of peers for the mesh network (D in the spec, default is 6).
    pub fn mesh_n(&mut self, mesh_n: usize) -> &mut Self {
        self.config.mesh_n = mesh_n;
        self
    }

    /// Minimum number of peers in mesh network before adding more (D_lo in the spec, default is 4).
    pub fn mesh_n_low(&mut self, mesh_n_low: usize) -> &mut Self {
        self.config.mesh_n_low = mesh_n_low;
        self
    }

    /// Maximum number of peers in mesh network before removing some (D_high in the spec, default
    /// is 12).
    pub fn mesh_n_high(&mut self, mesh_n_high: usize) -> &mut Self {
        self.config.mesh_n_high = mesh_n_high;
        self
    }

    /// Affects how peers are selected when pruning a mesh due to over subscription.
    ///
    /// At least [`Self::retain_scores`] of the retained peers will be high-scoring, while the remainder are
    /// chosen randomly (D_score in the spec, default is 4).
    pub fn retain_scores(&mut self, retain_scores: usize) -> &mut Self {
        self.config.retain_scores = retain_scores;
        self
    }

    /// Minimum number of peers to emit gossip to during a heartbeat (D_lazy in the spec,
    /// default is 6).
    pub fn gossip_lazy(&mut self, gossip_lazy: usize) -> &mut Self {
        self.config.gossip_lazy = gossip_lazy;
        self
    }

    /// Affects how many peers we will emit gossip to at each heartbeat.
    ///
    /// We will send gossip to `gossip_factor * (total number of non-mesh peers)`, or
    /// `gossip_lazy`, whichever is greater. The default is 0.25.
    pub fn gossip_factor(&mut self, gossip_factor: f64) -> &mut Self {
        self.config.gossip_factor = gossip_factor;
        self
    }

    /// Initial delay in each heartbeat (default is 5 seconds).
    pub fn heartbeat_initial_delay(&mut self, heartbeat_initial_delay: Duration) -> &mut Self {
        self.config.heartbeat_initial_delay = heartbeat_initial_delay;
        self
    }

    /// Time between each heartbeat (default is 1 second).
    pub fn heartbeat_interval(&mut self, heartbeat_interval: Duration) -> &mut Self {
        self.config.heartbeat_interval = heartbeat_interval;
        self
    }

    /// The number of heartbeat ticks until we recheck the connection to explicit peers and
    /// reconnecting if necessary (default 300).
    pub fn check_explicit_peers_ticks(&mut self, check_explicit_peers_ticks: u64) -> &mut Self {
        self.config.check_explicit_peers_ticks = check_explicit_peers_ticks;
        self
    }

    /// Time to live for fanout peers (default is 60 seconds).
    pub fn fanout_ttl(&mut self, fanout_ttl: Duration) -> &mut Self {
        self.config.fanout_ttl = fanout_ttl;
        self
    }

    /// The maximum byte size for each gossip (default is 2048 bytes).
    pub fn max_transmit_size(&mut self, max_transmit_size: usize) -> &mut Self {
        self.config.max_transmit_size = max_transmit_size;
        self
    }

    /// Duplicates are prevented by storing message id's of known messages in an LRU time cache.
    /// This settings sets the time period that messages are stored in the cache. Duplicates can be
    /// received if duplicate messages are sent at a time greater than this setting apart. The
    /// default is 1 minute.
    pub fn duplicate_cache_time(&mut self, cache_size: Duration) -> &mut Self {
        self.config.duplicate_cache_time = cache_size;
        self
    }

    /// When set, prevents automatic forwarding of all received messages. This setting
    /// allows a user to validate the messages before propagating them to their peers. If set,
    /// the user must manually call [`crate::Gossipsub::report_message_validation_result()`] on the
    /// behaviour to forward a message once validated.
    pub fn validate_messages(&mut self) -> &mut Self {
        self.config.validate_messages = true;
        self
    }

    /// Determines the level of validation used when receiving messages. See [`ValidationMode`]
    /// for the available types. The default is ValidationMode::Strict.
    pub fn validation_mode(&mut self, validation_mode: ValidationMode) -> &mut Self {
        self.config.validation_mode = validation_mode;
        self
    }

    /// A user-defined function allowing the user to specify the message id of a gossipsub message.
    /// The default value is to concatenate the source peer id with a sequence number. Setting this
    /// parameter allows the user to address packets arbitrarily. One example is content based
    /// addressing, where this function may be set to `hash(message)`. This would prevent messages
    /// of the same content from being duplicated.
    ///
    /// The function takes a [`GossipsubMessage`] as input and outputs a String to be
    /// interpreted as the message id.
    pub fn message_id_fn(&mut self, id_fn: fn(&GossipsubMessage) -> MessageId) -> &mut Self {
        self.config.message_id_fn = id_fn;
        self
    }

    /// A user-defined optional function that computes fast ids from raw messages. This can be used
    /// to avoid possibly expensive transformations from [`RawGossipsubMessage`] to
    /// [`GossipsubMessage`] for duplicates. Two semantically different messages must always
    /// have different fast message ids, but it is allowed that two semantically identical messages
    /// have different fast message ids as long as the message_id_fn produces the same id for them.
    ///
    /// The function takes a [`RawGossipsubMessage`] as input and outputs a String to be interpreted
    /// as the fast message id. Default is None.
    pub fn fast_message_id_fn(
        &mut self,
        fast_id_fn: fn(&RawGossipsubMessage) -> FastMessageId,
    ) -> &mut Self {
        self.config.fast_message_id_fn = Some(fast_id_fn);
        self
    }

    /// Enables Peer eXchange. This should be enabled in bootstrappers and other well
    /// connected/trusted nodes. The default is true.
    pub fn do_px(&mut self) -> &mut Self {
        self.config.do_px = true;
        self
    }

    /// Controls the number of peers to include in prune Peer eXchange.
    ///
    /// When we prune a peer that's eligible for PX (has a good score, etc), we will try to
    /// send them signed peer records for up to [`Self::prune_peers] other peers that we
    /// know of. It is recommended that this value is larger than [`Self::mesh_n_high`] so that the
    /// pruned peer can reliably form a full mesh. The default is 16.
    pub fn prune_peers(&mut self, prune_peers: usize) -> &mut Self {
        self.config.prune_peers = prune_peers;
        self
    }

    /// Controls the backoff time for pruned peers. This is how long
    /// a peer must wait before attempting to graft into our mesh again after being pruned.
    /// When pruning a peer, we send them our value of [`Self::prune_backoff`] so they know
    /// the minimum time to wait. Peers running older versions may not send a backoff time,
    /// so if we receive a prune message without one, we will wait at least [`Self::prune_backoff`]
    /// before attempting to re-graft. The default is one minute.
    pub fn prune_backoff(&mut self, prune_backoff: Duration) -> &mut Self {
        self.config.prune_backoff = prune_backoff;
        self
    }

    /// Number of heartbeat slots considered as slack for backoffs. This gurantees that we wait
    /// at least backoff_slack heartbeats after a backoff is over before we try to graft. This
    /// solves problems occuring through high latencies. In particular if
    /// `backoff_slack * heartbeat_interval` is longer than any latencies between processing
    /// prunes on our side and processing prunes on the receiving side this guarantees that we
    /// get not punished for too early grafting. The default is 1.
    pub fn backoff_slack(&mut self, backoff_slack: u32) -> &mut Self {
        self.config.backoff_slack = backoff_slack;
        self
    }

    /// Whether to do flood publishing or not. If enabled newly created messages will always be
    /// sent to all peers that are subscribed to the topic and have a good enough score.
    /// The default is true.
    pub fn flood_publish(&mut self, flood_publish: bool) -> &mut Self {
        self.config.flood_publish = flood_publish;
        self
    }

    /// If a GRAFT comes before `graft_flood_threshold` has elapsed since the last PRUNE,
    /// then there is an extra score penalty applied to the peer through P7.
    pub fn graft_flood_threshold(&mut self, graft_flood_threshold: Duration) -> &mut Self {
        self.config.graft_flood_threshold = graft_flood_threshold;
        self
    }

    /// Minimum number of outbound peers in the mesh network before adding more (D_out in the spec).
    /// This value must be smaller or equal than `mesh_n / 2` and smaller than `mesh_n_low`.
    /// The default is 2.
    pub fn mesh_outbound_min(&mut self, mesh_outbound_min: usize) -> &mut Self {
        self.config.mesh_outbound_min = mesh_outbound_min;
        self
    }

    /// Number of heartbeat ticks that specifcy the interval in which opportunistic grafting is
    /// applied. Every `opportunistic_graft_ticks` we will attempt to select some high-scoring mesh
    /// peers to replace lower-scoring ones, if the median score of our mesh peers falls below a
    /// threshold (see https://godoc.org/github.com/libp2p/go-libp2p-pubsub#PeerScoreThresholds).
    /// The default is 60.
    pub fn opportunistic_graft_ticks(&mut self, opportunistic_graft_ticks: u64) -> &mut Self {
        self.config.opportunistic_graft_ticks = opportunistic_graft_ticks;
        self
    }

    /// Controls how many times we will allow a peer to request the same message id through IWANT
    /// gossip before we start ignoring them. This is designed to prevent peers from spamming us
    /// with requests and wasting our resources.
    pub fn gossip_retransimission(&mut self, gossip_retransimission: u32) -> &mut Self {
        self.config.gossip_retransimission = gossip_retransimission;
        self
    }

    /// The maximum number of new peers to graft to during opportunistic grafting. The default is 2.
    pub fn opportunistic_graft_peers(&mut self, opportunistic_graft_peers: usize) -> &mut Self {
        self.config.opportunistic_graft_peers = opportunistic_graft_peers;
        self
    }

    /// The maximum number of messages we will process in a given RPC. If this is unset, there is
    /// no limit. The default is None.
    pub fn max_messages_per_rpc(&mut self, max: Option<usize>) -> &mut Self {
        self.config.max_messages_per_rpc = max;
        self
    }

    /// The maximum number of messages to include in an IHAVE message.
    /// Also controls the maximum number of IHAVE ids we will accept and request with IWANT from a
    /// peer within a heartbeat, to protect from IHAVE floods. You should adjust this value from the
    /// default if your system is pushing more than 5000 messages in GossipSubHistoryGossip
    /// heartbeats; with the defaults this is 1666 messages/s. The default is 5000.
    pub fn max_ihave_length(&mut self, max_ihave_length: usize) -> &mut Self {
        self.config.max_ihave_length = max_ihave_length;
        self
    }

    /// GossipSubMaxIHaveMessages is the maximum number of IHAVE messages to accept from a peer
    /// within a heartbeat.
    pub fn max_ihave_messages(&mut self, max_ihave_messages: usize) -> &mut Self {
        self.config.max_ihave_messages = max_ihave_messages;
        self
    }

    /// By default, gossipsub will reject messages that are sent to us that has the same message
    /// source as we have specified locally. Enabling this, allows these messages and prevents
    /// penalizing the peer that sent us the message. Default is false.
    pub fn allow_self_origin(&mut self, allow_self_origin: bool) -> &mut Self {
        self.config.allow_self_origin = allow_self_origin;
        self
    }

    /// Time to wait for a message requested through IWANT following an IHAVE advertisement.
    /// If the message is not received within this window, a broken promise is declared and
    /// the router may apply behavioural penalties. The default is 3 seconds.
    pub fn iwant_followup_time(&mut self, iwant_followup_time: Duration) -> &mut Self {
        self.config.iwant_followup_time = iwant_followup_time;
        self
    }

    /// Enable support for flooodsub peers.
    pub fn support_floodsub(&mut self) -> &mut Self {
        self.config.support_floodsub = true;
        self
    }

    /// Published message ids time cache duration. The default is 10 seconds.
    pub fn published_message_ids_cache_time(
        &mut self,
        published_message_ids_cache_time: Duration,
    ) -> &mut Self {
        self.config.published_message_ids_cache_time = published_message_ids_cache_time;
        self
    }

    /// Constructs a [`GossipsubConfig`] from the given configuration and validates the settings.
    pub fn build(&self) -> Result<GossipsubConfig, &str> {
        // check all constraints on config

        if self.config.max_transmit_size < 100 {
            return Err("The maximum transmission size must be greater than 100 to permit basic control messages");
        }

        if self.config.history_length < self.config.history_gossip {
            return Err(
                "The history_length must be greater than or equal to the history_gossip \
                length",
            );
        }

        if !(self.config.mesh_outbound_min < self.config.mesh_n_low
            && self.config.mesh_n_low <= self.config.mesh_n
            && self.config.mesh_n <= self.config.mesh_n_high)
        {
            return Err("The following inequality doesn't hold \
                mesh_outbound_min < mesh_n_low <= mesh_n <= mesh_n_high");
        }

        if self.config.mesh_outbound_min * 2 > self.config.mesh_n {
            return Err(
                "The following inequality doesn't hold mesh_outbound_min <= self.config.mesh_n / 2",
            );
        }
        Ok(self.config.clone())
    }
}

impl std::fmt::Debug for GossipsubConfig {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let mut builder = f.debug_struct("GossipsubConfig");
        let _ = builder.field("protocol_id_prefix", &self.protocol_id_prefix);
        let _ = builder.field("history_length", &self.history_length);
        let _ = builder.field("history_gossip", &self.history_gossip);
        let _ = builder.field("mesh_n", &self.mesh_n);
        let _ = builder.field("mesh_n_low", &self.mesh_n_low);
        let _ = builder.field("mesh_n_high", &self.mesh_n_high);
        let _ = builder.field("retain_scores", &self.retain_scores);
        let _ = builder.field("gossip_lazy", &self.gossip_lazy);
        let _ = builder.field("gossip_factor", &self.gossip_factor);
        let _ = builder.field("heartbeat_initial_delay", &self.heartbeat_initial_delay);
        let _ = builder.field("heartbeat_interval", &self.heartbeat_interval);
        let _ = builder.field("fanout_ttl", &self.fanout_ttl);
        let _ = builder.field("max_transmit_size", &self.max_transmit_size);
        let _ = builder.field("duplicate_cache_time", &self.duplicate_cache_time);
        let _ = builder.field("validate_messages", &self.validate_messages);
        let _ = builder.field("validation_mode", &self.validation_mode);
        let _ = builder.field("allow_self_origin", &self.allow_self_origin);
        let _ = builder.field("do_px", &self.do_px);
        let _ = builder.field("prune_peers", &self.prune_peers);
        let _ = builder.field("prune_backoff", &self.prune_backoff);
        let _ = builder.field("backoff_slack", &self.backoff_slack);
        let _ = builder.field("flood_publish", &self.flood_publish);
        let _ = builder.field("graft_flood_threshold", &self.graft_flood_threshold);
        let _ = builder.field("mesh_outbound_min", &self.mesh_outbound_min);
        let _ = builder.field("opportunistic_graft_ticks", &self.opportunistic_graft_ticks);
        let _ = builder.field("opportunistic_graft_peers", &self.opportunistic_graft_peers);
        let _ = builder.field("max_messages_per_rpc", &self.max_messages_per_rpc);
        let _ = builder.field("max_ihave_length", &self.max_ihave_length);
        let _ = builder.field("max_ihave_messages", &self.max_ihave_messages);
        let _ = builder.field("iwant_followup_time", &self.iwant_followup_time);
        let _ = builder.field("support_floodsub", &self.support_floodsub);
        let _ = builder.field(
            "published_message_ids_cache_time",
            &self.published_message_ids_cache_time,
        );
        builder.finish()
    }
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn create_thing() {
        let builder: GossipsubConfig = GossipsubConfigBuilder::default()
            .protocol_id_prefix("purple")
            .build()
            .unwrap();

        dbg!(builder);
    }
}