ferogram/

peer_cache.rs

// Copyright (c) Ankit Chaubey <ankitchaubey.dev@gmail.com>
//
// ferogram: async Telegram MTProto client in Rust
// https://github.com/ankit-chaubey/ferogram
//
// Licensed under either the MIT License or the Apache License 2.0.
// See the LICENSE-MIT or LICENSE-APACHE file in this repository:
// https://github.com/ankit-chaubey/ferogram
//
// Feel free to use, modify, and share this code.
// Please keep this notice when redistributing.

use std::collections::{HashMap, HashSet};

use ferogram_tl_types as tl;

use crate::errors::InvocationError;

/// Opt-in experimental behaviours that deviate from strict Telegram spec.
///
/// All flags default to `false` (safe / spec-correct).  Enable only what you
/// need after reading the per-field warnings.
///
/// # Example
/// ```rust,no_run
/// use ferogram::{Client, ExperimentalFeatures};
///
/// # #[tokio::main] async fn main() -> Result<(), Box<dyn std::error::Error>> {
/// let (client, _sd) = Client::builder()
///     .api_id(12345)
///     .api_hash("abc")
///     .experimental_features(ExperimentalFeatures {
///         allow_zero_hash: true,   // bot-only; omit for user accounts
///         ..Default::default()
///     })
///     .connect().await?;
/// # Ok(()) }
/// ```
#[derive(Clone, Debug, Default)]
pub struct ExperimentalFeatures {
    /// When no `access_hash` is cached for a user or channel, fall back to
    /// `access_hash = 0` instead of returning [`InvocationError::PeerNotCached`].
    ///
    /// **Bot accounts only.** The Telegram spec explicitly permits `hash = 0`
    /// for bots when only a min-hash is available.  On user accounts this
    /// produces `USER_ID_INVALID` / `CHANNEL_INVALID`.
    pub allow_zero_hash: bool,

    /// When resolving a min-user via `InputPeerUserFromMessage`, if the
    /// containing channel's hash is not cached, proceed with
    /// `channel access_hash = 0` instead of returning
    /// [`InvocationError::PeerNotCached`].
    ///
    /// Almost always wrong.  The inner `InputPeerChannel { access_hash: 0 }`
    /// makes the whole `InputPeerUserFromMessage` invalid and Telegram will
    /// reject it.  Only useful for debugging / testing.
    pub allow_missing_channel_hash: bool,

    /// *(Reserved  - not yet implemented.)*
    ///
    /// When set, a cache miss would automatically call `users.getUsers` /
    /// `channels.getChannels` to fetch a fresh `access_hash` before
    /// constructing the `InputPeer`.  Currently has no effect.
    pub auto_resolve_peers: bool,
}

/// Caches access hashes for users and channels so every API call carries the
/// correct hash without re-resolving peers.
/// Discriminates the kind of peer stored in `PeerCache::username_to_peer`.
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum PeerType {
    User,
    Channel,
    Chat,
}

///
/// All fields are `pub` so that `save_session` / `connect` can read/write them
/// directly, and so that advanced callers can inspect the cache.
pub struct PeerCache {
    /// user_id -> access_hash (full users only, min=false)
    pub users: HashMap<i64, i64>,
    /// channel_id -> access_hash (full channels only, min=false)
    pub channels: HashMap<i64, i64>,
    /// Regular group chat IDs (Chat::Chat / ChatForbidden).
    /// Groups need no access_hash; track existence for peer validation.
    pub chats: HashSet<i64>,
    /// Channel IDs seen with min=true. These are real channels but have no
    /// valid access_hash. Stored separately so they are NEVER confused with
    /// regular groups. DO NOT put min channels in `chats`. A min channel must
    /// never become InputPeerChat  - that causes fatal RPC failures.
    pub channels_min: HashSet<i64>,
    /// user_id -> (peer_id, msg_id) for min users seen in a message context.
    /// Min users have an invalid access_hash; they must be referenced via
    /// InputPeerUserFromMessage using the peer and message where they appeared.
    pub min_contexts: HashMap<i64, (i64, i32)>,
    /// Reverse index: lowercase username → (id, PeerType).
    /// Populated by cache_user / cache_chat; always overwritten on update
    /// (usernames can change).
    pub username_to_peer: HashMap<String, (i64, PeerType)>,
    /// Reverse index: E.164 phone → user_id.
    pub phone_to_user: HashMap<String, i64>,
    /// Experimental opt-ins that change error-vs-fallback behaviour.
    experimental: ExperimentalFeatures,
}

impl Default for PeerCache {
    fn default() -> Self {
        Self::new(ExperimentalFeatures::default())
    }
}

impl PeerCache {
    /// Create a new empty cache with the given experimental-feature flags.
    pub fn new(experimental: ExperimentalFeatures) -> Self {
        Self {
            users: HashMap::new(),
            channels: HashMap::new(),
            chats: HashSet::new(),
            channels_min: HashSet::new(),
            min_contexts: HashMap::new(),
            username_to_peer: HashMap::new(),
            phone_to_user: HashMap::new(),
            experimental,
        }
    }

    pub fn cache_user(&mut self, user: &tl::enums::User) {
        if let tl::enums::User::User(u) = user {
            if u.min {
                // min=true: access_hash is not valid; requires a message context.
            } else if let Some(hash) = u.access_hash {
                // Never overwrite a valid non-zero hash with zero.
                if hash != 0 {
                    self.users.insert(u.id, hash);
                } else {
                    self.users.entry(u.id).or_insert(0);
                }
                // Full user always supersedes any min context.
                self.min_contexts.remove(&u.id);
            }
            // Reverse indices (update even for min users so username lookup works)
            if let Some(ref uname) = u.username {
                self.username_to_peer
                    .insert(uname.to_lowercase(), (u.id, PeerType::User));
            }
            if let Some(ref phone) = u.phone {
                self.phone_to_user.insert(phone.clone(), u.id);
            }
        }
    }

    /// Cache a user that arrived in a message context.
    ///
    /// For min users (access_hash is invalid), stores the peer+msg context so
    /// they can later be referenced via `InputPeerUserFromMessage`.
    ///
    /// Uses **latest-wins** semantics: a newer message context replaces the
    /// stored one.  Recent messages are less likely to have been deleted.
    pub fn cache_user_with_context(&mut self, user: &tl::enums::User, peer_id: i64, msg_id: i32) {
        if let tl::enums::User::User(u) = user {
            if u.min {
                // Never downgrade a cached full user to a min context.
                if !self.users.contains_key(&u.id) {
                    // Latest-wins: overwrite with the most recent message context.
                    self.min_contexts.insert(u.id, (peer_id, msg_id));
                }
            } else if let Some(hash) = u.access_hash {
                // Never overwrite a non-zero hash with zero.
                if hash != 0 {
                    self.users.insert(u.id, hash);
                } else {
                    self.users.entry(u.id).or_insert(0);
                }
                self.min_contexts.remove(&u.id);
            }
            // Reverse indices
            if let Some(ref uname) = u.username {
                self.username_to_peer
                    .insert(uname.to_lowercase(), (u.id, PeerType::User));
            }
            if let Some(ref phone) = u.phone {
                self.phone_to_user.insert(phone.clone(), u.id);
            }
        }
    }

    pub fn cache_chat(&mut self, chat: &tl::enums::Chat) {
        match chat {
            tl::enums::Chat::Channel(c) => {
                if c.min {
                    // min channel: no access_hash available.
                    // Store in channels_min; never put in chats (InputPeerChat fails).
                    if !self.channels.contains_key(&c.id) {
                        self.channels_min.insert(c.id);
                    }
                } else if let Some(hash) = c.access_hash {
                    // Never overwrite a valid non-zero hash with zero.
                    if hash != 0 {
                        self.channels.insert(c.id, hash);
                    } else {
                        self.channels.entry(c.id).or_insert(0);
                    }
                    // Full channel supersedes any min tracking.
                    self.channels_min.remove(&c.id);
                }
                // Reverse username index for channels (update regardless of min)
                if let Some(ref uname) = c.username {
                    self.username_to_peer
                        .insert(uname.to_lowercase(), (c.id, PeerType::Channel));
                }
            }
            tl::enums::Chat::ChannelForbidden(c) => {
                // Only store if the hash is non-zero.
                if c.access_hash != 0 {
                    self.channels.insert(c.id, c.access_hash);
                } else {
                    self.channels.entry(c.id).or_insert(0);
                }
                self.channels_min.remove(&c.id);
            }
            tl::enums::Chat::Chat(c) => {
                // Regular groups need no access_hash; track existence only.
                self.chats.insert(c.id);
            }
            tl::enums::Chat::Forbidden(c) => {
                self.chats.insert(c.id);
            }
            _ => {}
        }
    }

    pub fn cache_users(&mut self, users: &[tl::enums::User]) {
        for u in users {
            self.cache_user(u);
        }
    }

    pub fn cache_chats(&mut self, chats: &[tl::enums::Chat]) {
        for c in chats {
            self.cache_chat(c);
        }
    }

    /// Store an already-resolved `InputPeer`'s access hash into the cache.
    ///
    /// Called when a caller provides a `PeerRef::Input` so that the subsequent
    /// `peer_to_input` lookup succeeds without an RPC.
    pub fn cache_input_peer(&mut self, ip: &tl::enums::InputPeer) {
        match ip {
            tl::enums::InputPeer::User(u) => {
                if u.access_hash != 0 {
                    self.users.insert(u.user_id, u.access_hash);
                } else {
                    self.users.entry(u.user_id).or_insert(0);
                }
                self.min_contexts.remove(&u.user_id);
            }
            tl::enums::InputPeer::Channel(c) => {
                if c.access_hash != 0 {
                    self.channels.insert(c.channel_id, c.access_hash);
                } else {
                    self.channels.entry(c.channel_id).or_insert(0);
                }
                self.channels_min.remove(&c.channel_id);
            }
            tl::enums::InputPeer::Chat(c) => {
                self.chats.insert(c.chat_id);
            }
            // UserFromMessage: cache the container peer's hash AND record the
            // min_context so peer_to_input() can rebuild InputPeerUserFromMessage.
            tl::enums::InputPeer::UserFromMessage(u) => {
                // Cache the container peer's access hash
                self.cache_input_peer(&u.peer);
                // Extract container peer_id for the min_context entry
                let container_peer_id = match &u.peer {
                    tl::enums::InputPeer::Channel(c) => Some(c.channel_id),
                    tl::enums::InputPeer::Chat(c) => Some(c.chat_id),
                    tl::enums::InputPeer::User(pu) => Some(pu.user_id),
                    tl::enums::InputPeer::PeerSelf => Some(0i64),
                    _ => None,
                };
                if let Some(peer_id) = container_peer_id {
                    // Only set min_context if there is no full hash cached yet.
                    if !self.users.contains_key(&u.user_id) {
                        self.min_contexts.insert(u.user_id, (peer_id, u.msg_id));
                    }
                }
            }
            // ChannelFromMessage: cache the container peer hash and channel entry.
            tl::enums::InputPeer::ChannelFromMessage(c) => {
                self.cache_input_peer(&c.peer);
                // The channel itself has no standalone hash here; mark as known
                // via channels_min so we don't lose track of it.
                self.channels_min.insert(c.channel_id);
            }
            tl::enums::InputPeer::Empty | tl::enums::InputPeer::PeerSelf => {}
        }
    }

    /// Remove stale cache entries when Telegram rejects them with
    /// `PEER_ID_INVALID`, `CHANNEL_INVALID`, `USER_ID_INVALID`, or
    /// `CHANNEL_PRIVATE`.  The caller should then retry the operation.
    pub fn invalidate_peer(&mut self, peer: &tl::enums::Peer) {
        match peer {
            tl::enums::Peer::User(u) => {
                self.users.remove(&u.user_id);
                self.min_contexts.remove(&u.user_id);
            }
            tl::enums::Peer::Channel(c) => {
                self.channels.remove(&c.channel_id);
                self.channels_min.remove(&c.channel_id);
            }
            tl::enums::Peer::Chat(_) => {} // basic groups have no hash to invalidate
        }
    }

    pub(crate) fn user_input_peer(
        &self,
        user_id: i64,
    ) -> Result<tl::enums::InputPeer, InvocationError> {
        if user_id == 0 {
            return Ok(tl::enums::InputPeer::PeerSelf);
        }

        // Full hash: best case.
        if let Some(&hash) = self.users.get(&user_id) {
            return Ok(tl::enums::InputPeer::User(tl::types::InputPeerUser {
                user_id,
                access_hash: hash,
            }));
        }

        // Min user: resolve via the message context where they were seen.
        if let Some(&(peer_id, msg_id)) = self.min_contexts.get(&user_id) {
            // The containing peer can be a channel, a basic group, or a DM user.
            // Build the correct InputPeer variant for each case.
            let container = if let Some(&hash) = self.channels.get(&peer_id) {
                tl::enums::InputPeer::Channel(tl::types::InputPeerChannel {
                    channel_id: peer_id,
                    access_hash: hash,
                })
            } else if self.channels_min.contains(&peer_id) {
                if self.experimental.allow_missing_channel_hash {
                    tracing::warn!(
                        "[ferogram] PeerCache: channel {peer_id} is a min channel \
                         (contains min user {user_id}), using hash=0. \
                         This will likely cause CHANNEL_INVALID. \
                         Resolve the channel first."
                    );
                    tl::enums::InputPeer::Channel(tl::types::InputPeerChannel {
                        channel_id: peer_id,
                        access_hash: 0,
                    })
                } else {
                    return Err(InvocationError::PeerNotCached(format!(
                        "min user {user_id} was seen in channel {peer_id}, \
                         but that channel is only known as a min channel (no access_hash). \
                         Resolve the channel first, or enable \
                         ExperimentalFeatures::allow_missing_channel_hash."
                    )));
                }
            } else if self.chats.contains(&peer_id) {
                // Basic group: no access_hash needed.
                tl::enums::InputPeer::Chat(tl::types::InputPeerChat { chat_id: peer_id })
            } else if let Some(&hash) = self.users.get(&peer_id) {
                // DM: min user was seen in a direct message with another user.
                tl::enums::InputPeer::User(tl::types::InputPeerUser {
                    user_id: peer_id,
                    access_hash: hash,
                })
            } else {
                return Err(InvocationError::PeerNotCached(format!(
                    "min user {user_id} was seen in peer {peer_id}, \
                     but that peer is not cached (not a known channel, chat, or user). \
                     Ensure the containing chat flows through the update loop first."
                )));
            };
            return Ok(tl::enums::InputPeer::UserFromMessage(Box::new(
                tl::types::InputPeerUserFromMessage {
                    peer: container,
                    msg_id,
                    user_id,
                },
            )));
        }

        // No hash at all.
        if self.experimental.allow_zero_hash {
            tracing::warn!(
                "[ferogram] PeerCache: no access_hash for user {user_id}, using 0. \
                 Valid for bots only (Telegram spec). On user accounts this will \
                 cause USER_ID_INVALID. Resolve the peer first or disable \
                 ExperimentalFeatures::allow_zero_hash."
            );
            Ok(tl::enums::InputPeer::User(tl::types::InputPeerUser {
                user_id,
                access_hash: 0,
            }))
        } else {
            Err(InvocationError::PeerNotCached(format!(
                "no access_hash cached for user {user_id}. \
                 Ensure at least one message from this user flows through the \
                 update loop before using them as a peer, or call \
                 client.resolve_peer() first."
            )))
        }
    }

    fn channel_input_peer(&self, channel_id: i64) -> Result<tl::enums::InputPeer, InvocationError> {
        if let Some(&hash) = self.channels.get(&channel_id) {
            return Ok(tl::enums::InputPeer::Channel(tl::types::InputPeerChannel {
                channel_id,
                access_hash: hash,
            }));
        }

        if self.experimental.allow_zero_hash {
            tracing::warn!(
                "[ferogram] PeerCache: no access_hash for channel {channel_id}, using 0. \
                 Valid for bots only (Telegram spec). On user accounts this will \
                 cause CHANNEL_INVALID. Resolve the peer first or disable \
                 ExperimentalFeatures::allow_zero_hash."
            );
            Ok(tl::enums::InputPeer::Channel(tl::types::InputPeerChannel {
                channel_id,
                access_hash: 0,
            }))
        } else {
            Err(InvocationError::PeerNotCached(format!(
                "no access_hash cached for channel {channel_id}. \
                 Ensure the channel flows through the update loop before using \
                 it as a peer, or call client.resolve_peer() first."
            )))
        }
    }

    pub fn peer_to_input(
        &self,
        peer: &tl::enums::Peer,
    ) -> Result<tl::enums::InputPeer, InvocationError> {
        match peer {
            tl::enums::Peer::User(u) => self.user_input_peer(u.user_id),
            tl::enums::Peer::Chat(c) => Ok(tl::enums::InputPeer::Chat(tl::types::InputPeerChat {
                chat_id: c.chat_id,
            })),
            tl::enums::Peer::Channel(c) => self.channel_input_peer(c.channel_id),
        }
    }
}