//! This agent's three Honcho workspaces through `roncho`'s blocking client (M5c spec, section 6):
//! one client per workspace, with its own key, and the steps that make sure a workspace, a peer
//! and a session exist before anything is written to them. Nothing here keeps or logs a response
//! body or a key: an error is its kind and its status.

use std::collections::{HashMap, HashSet};
use std::ffi::OsString;
use std::time::Duration;

use bxcore::secrets;
use roncho::blocking::{Client, Error};
use roncho::{PeerCreate, SessionCreate, SessionPeerConfig, WorkspaceCreate};
use serde_json::{Map, Value, json};

use crate::honcho::config::{FLEET_KEY, HonchoConfig, TRUSTED_KEY, UNTRUSTED_KEY};
use crate::honcho::ledger::Workspace;
use crate::honcho::naming::HonchoSession;

/// How long a connection may take, and a read may go without a byte.
pub const CONNECT: Duration = Duration::from_secs(5);
pub const READ: Duration = Duration::from_secs(30);
/// A chat's read: a non-streamed chat sends nothing until it is done (M5c spec, section 9).
pub const CHAT_READ: Duration = Duration::from_secs(150);

/// The timeouts a client is built with. Tests shorten them.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct Timeouts {
    pub connect: Duration,
    pub read: Duration,
}

impl Timeouts {
    pub const WRITES: Timeouts = Timeouts {
        connect: CONNECT,
        read: READ,
    };
}

/// Why a call to Honcho failed: its kind and status only, never the response's body.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum HonchoError {
    /// No answer that counts: no connection, a timeout, a closed socket, or a 5xx. Try again later.
    Unreachable {
        kind: &'static str,
        status: Option<u16>,
    },
    /// Honcho answered, and will answer the same again: a 4xx, a redirect, or a body that is not
    /// what `roncho` expects.
    Refused {
        kind: &'static str,
        status: Option<u16>,
    },
    /// The workspace's key was refused (401 or 403).
    KeyRefused { status: u16 },
}

impl HonchoError {
    pub fn kind(&self) -> &'static str {
        match self {
            HonchoError::Unreachable { kind, .. } | HonchoError::Refused { kind, .. } => kind,
            HonchoError::KeyRefused { .. } => "key-refused",
        }
    }

    pub fn status(&self) -> Option<u16> {
        match self {
            HonchoError::Unreachable { status, .. } | HonchoError::Refused { status, .. } => {
                *status
            }
            HonchoError::KeyRefused { status } => Some(*status),
        }
    }
}

impl std::fmt::Display for HonchoError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let what = match self {
            HonchoError::Unreachable { .. } => "Honcho is unreachable",
            HonchoError::Refused { .. } => "Honcho refused the request",
            HonchoError::KeyRefused { .. } => "Honcho refused the key",
        };
        match self.status() {
            Some(status) => write!(f, "{what} ({}, HTTP {status})", self.kind()),
            None => write!(f, "{what} ({})", self.kind()),
        }
    }
}

impl std::error::Error for HonchoError {}

/// `roncho`'s error as a `HonchoError`. Its text is dropped: a `Status` or `Decode` error carries
/// up to 4 KiB of the response, which can echo memory text (a 422 echoes the whole input).
pub fn classify(error: &Error) -> HonchoError {
    let unreachable = |kind, status| HonchoError::Unreachable { kind, status };
    let refused = |kind, status| HonchoError::Refused { kind, status };
    match error {
        Error::Connect(_) => unreachable("connect", None),
        Error::Timeout => unreachable("timeout", None),
        Error::Closed => unreachable("closed", None),
        Error::Io(_) => unreachable("io", None),
        Error::Status { status, .. } if *status >= 500 => unreachable("server", Some(*status)),
        Error::Status { status, .. } => refused("status", Some(*status)),
        Error::Unauthorized { status } => HonchoError::KeyRefused { status: *status },
        Error::Redirect { status } => refused("redirect", Some(*status)),
        Error::ActiveSessions { .. } => refused("active-sessions", Some(409)),
        Error::TooLarge => refused("too-large", None),
        Error::Decode(_) => refused("decode", None),
        Error::Stream(_) => refused("stream", None),
        Error::Config(_) => refused("config", None),
        _ => refused("other", None),
    }
}

/// What has been made sure of in one workspace during this run.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
enum Ensured {
    Workspace,
    Peer(String),
    Session(String),
}

/// The three clients, and what they have made sure of since `memoryd` started. After a restart
/// everything is made sure of again: each step is get-or-create, so that costs a request, no more.
#[derive(Debug)]
pub struct Clients {
    trusted: Client,
    untrusted: Client,
    fleet: Client,
    agent: String,
    owner: String,
    ensured: HashSet<(Workspace, Ensured)>,
}

/// The fleet workspace's configuration: nothing reasons over the fleet's notes (M5c spec,
/// section 6). All three are set, since Honcho checks each on its own.
pub fn fleet_configuration() -> Map<String, Value> {
    let mut map = Map::new();
    for feature in ["reasoning", "summary", "dream"] {
        map.insert(feature.to_string(), json!({ "enabled": false }));
    }
    map
}

/// A session's peers: the agent's, unobserved, and each speaker's, observed; no peer forms a
/// picture of the others.
pub fn session_peers(agent: &str, speakers: &[String]) -> HashMap<String, SessionPeerConfig> {
    let mut peers = HashMap::new();
    peers.insert(
        agent.to_string(),
        SessionPeerConfig::new()
            .observe_me(false)
            .observe_others(false),
    );
    for speaker in speakers {
        peers.insert(
            speaker.clone(),
            SessionPeerConfig::new()
                .observe_me(true)
                .observe_others(false),
        );
    }
    peers
}

/// A create that found the thing there (409) did what it was for.
fn created<T>(result: Result<T, Error>) -> Result<(), HonchoError> {
    match result {
        Ok(_) => Ok(()),
        Err(e) => match classify(&e) {
            HonchoError::Refused {
                status: Some(409), ..
            } => Ok(()),
            other => Err(other),
        },
    }
}

/// One workspace's client: no `roncho.toml` read, the timeouts given, the key when there is one.
pub(crate) fn client(
    url: &str,
    workspace: &str,
    key: Option<&secrets::Secret>,
    timeouts: Timeouts,
) -> Result<Client, String> {
    let mut builder = Client::builder()
        .without_config_file()
        .base_url(url)
        .workspace_id(workspace)
        .connect_timeout(timeouts.connect)
        .read_timeout(timeouts.read);
    if let Some(key) = key {
        builder = builder.api_key(key.expose());
    }
    builder
        .build()
        .map_err(|e| format!("the Honcho client for {workspace}: {e}"))
}

/// The key named `name` in `[secrets]`, if one is configured, read now.
pub(crate) fn key(
    config: &HonchoConfig,
    name: &str,
    env: &dyn Fn(&str) -> Option<OsString>,
    warnings: &mut Vec<String>,
) -> Result<Option<secrets::Secret>, String> {
    let Some(source) = config.keys.get(name) else {
        return Ok(None);
    };
    let loaded = secrets::load("memoryd", name, source, env).map_err(|e| e.to_string())?;
    warnings.extend(loaded.warning);
    Ok(Some(loaded.secret))
}

impl Clients {
    /// A client for each of the three workspaces, each with its key when one is configured. The
    /// warnings are the key files' plaintext warnings, for the caller to log. An error names the
    /// key or the workspace, never a key's value.
    pub fn new(
        config: &HonchoConfig,
        env: &dyn Fn(&str) -> Option<OsString>,
        timeouts: Timeouts,
    ) -> Result<(Clients, Vec<String>), String> {
        let mut warnings = Vec::new();
        let trusted_key = key(config, TRUSTED_KEY, env, &mut warnings)?;
        let untrusted_key = key(config, UNTRUSTED_KEY, env, &mut warnings)?;
        let fleet_key = key(config, FLEET_KEY, env, &mut warnings)?;
        let clients = Clients {
            trusted: client(&config.url, &config.trusted, trusted_key.as_ref(), timeouts)?,
            untrusted: client(
                &config.url,
                &config.untrusted,
                untrusted_key.as_ref(),
                timeouts,
            )?,
            fleet: client(&config.url, &config.fleet, fleet_key.as_ref(), timeouts)?,
            agent: config.agent.clone(),
            owner: config.owner.clone(),
            ensured: HashSet::new(),
        };
        Ok((clients, warnings))
    }

    /// The client of `workspace`.
    pub fn client(&self, workspace: Workspace) -> &Client {
        match workspace {
            Workspace::Trusted => &self.trusted,
            Workspace::Untrusted => &self.untrusted,
            Workspace::Fleet => &self.fleet,
        }
    }

    /// Make sure `workspace` exists; the fleet one is made with `fleet_configuration`, the other
    /// two with Honcho's defaults.
    pub fn ensure_workspace(&mut self, workspace: Workspace) -> Result<(), HonchoError> {
        let key = (workspace, Ensured::Workspace);
        if self.ensured.contains(&key) {
            return Ok(());
        }
        let client = self.client(workspace);
        let mut create = WorkspaceCreate::new(client.workspace_id());
        if workspace == Workspace::Fleet {
            create = create.with_configuration(fleet_configuration());
        }
        created(client.get_or_create_workspace(&create))?;
        self.ensured.insert(key);
        Ok(())
    }

    /// Make sure peer `peer` exists in `workspace`. The agent's own peer is made unobserved
    /// (`observe_me` false): Honcho draws no conclusions from the agent's own output.
    pub fn ensure_peer(&mut self, workspace: Workspace, peer: &str) -> Result<(), HonchoError> {
        let key = (workspace, Ensured::Peer(peer.to_string()));
        if self.ensured.contains(&key) {
            return Ok(());
        }
        let mut create = PeerCreate::new(peer);
        if peer == self.agent {
            let mut configuration = Map::new();
            configuration.insert("observe_me".to_string(), json!(false));
            create = create.with_configuration(configuration);
        }
        created(self.client(workspace).peer(&create))?;
        self.ensured.insert(key);
        Ok(())
    }

    /// Make sure `session` exists in `workspace`, with the agent's peer and its speakers' peers,
    /// after the workspace and every peer. A session must exist before a message is added to
    /// it: Honcho makes a missing one on the fly, with no peers configured.
    pub fn ensure_session(
        &mut self,
        workspace: Workspace,
        session: &HonchoSession,
    ) -> Result<(), HonchoError> {
        self.ensure_workspace(workspace)?;
        let agent = self.agent.clone();
        self.ensure_peer(workspace, &agent)?;
        for speaker in &session.speakers {
            self.ensure_peer(workspace, speaker)?;
        }
        let key = (workspace, Ensured::Session(session.name.clone()));
        if self.ensured.contains(&key) {
            return Ok(());
        }
        let peers = session_peers(&agent, &session.speakers);
        let create = SessionCreate::new(session.name.as_str()).with_peers(peers);
        created(self.client(workspace).session(&create))?;
        self.ensured.insert(key);
        Ok(())
    }

    /// Make sure memory session `name` (a Boxmaker session's `<id>_memory`) exists in
    /// `workspace`, after the workspace, the agent's peer and the owner's. It holds conclusions,
    /// no messages, so neither peer observes (M5c spec, section 4).
    pub fn ensure_memory_session(
        &mut self,
        workspace: Workspace,
        name: &str,
    ) -> Result<(), HonchoError> {
        self.ensure_workspace(workspace)?;
        let (agent, owner) = (self.agent.clone(), self.owner.clone());
        self.ensure_peer(workspace, &agent)?;
        self.ensure_peer(workspace, &owner)?;
        let key = (workspace, Ensured::Session(name.to_string()));
        if self.ensured.contains(&key) {
            return Ok(());
        }
        let unobserved = || {
            SessionPeerConfig::new()
                .observe_me(false)
                .observe_others(false)
        };
        let mut peers = HashMap::new();
        peers.insert(agent, unobserved());
        peers.insert(owner, unobserved());
        let create = SessionCreate::new(name).with_peers(peers);
        created(self.client(workspace).session(&create))?;
        self.ensured.insert(key);
        Ok(())
    }

    /// Delete conclusion `id` in `workspace`. Gone already (404) counts as done.
    pub fn delete_conclusion(&self, workspace: Workspace, id: &str) -> Result<(), HonchoError> {
        match self.client(workspace).delete_conclusion(id) {
            Ok(()) => Ok(()),
            Err(e) => match classify(&e) {
                HonchoError::Refused {
                    status: Some(404), ..
                } => Ok(()),
                other => Err(other),
            },
        }
    }
}