//! Read-only project work-state read model.
//!
//! This module composes existing runtime state only: the project agent manifest,
//! live session registries and the input mediator busy state. It performs no I/O
//! beyond loading the manifest through the existing context store and creates no
//! durable projection.

mod actions;

pub use actions::{
    AttachLiveAgent, AttachLiveAgentInput, AttachLiveAgentOutput, StopLiveAgent,
    StopLiveAgentInput, StopLiveAgentOutput,
};

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

use domain::input::{AgentBusyState, InputSource};
use domain::ports::AgentContextStore;
use domain::{
    AgentId, AgentQueueSnapshot, ConversationId, ConversationLog, ConversationTurn, Handoff,
    HandoffStore, InputMediator, NodeId, ProfileId, Project, ProjectPath, QueuedTicketSnapshot,
    SessionId, TicketId, TurnId, TurnRole,
};

use crate::error::AppError;
use crate::terminal::{LiveSessionKind, LiveSessionSnapshot, LiveSessions};
use crate::HandoffProvider;

/// Maximum length (in characters) of a derived [`AgentTicketState::task_preview`].
///
/// The full task can be a very long prompt; the panel only needs a scannable
/// excerpt, with [`AgentTicketState::task_len`] signalling there is more.
const TASK_PREVIEW_MAX_CHARS: usize = 160;

/// Maximum length (in characters) of a conversation [`ConversationWorkSummary::summary_preview`].
const HANDOFF_PREVIEW_MAX_CHARS: usize = 480;

/// Maximum length (in characters) of a conversation [`ConversationWorkSummary::objective_preview`].
const OBJECTIVE_PREVIEW_MAX_CHARS: usize = 160;

/// Maximum number of recent turns surfaced in a [`ConversationWorkSummary::recent_turns`] fallback.
const RECENT_TURNS_MAX: usize = 3;

/// Maximum length (in characters) of a [`ConversationTurnWorkPreview::text_preview`].
const TURN_PREVIEW_MAX_CHARS: usize = 220;

/// Input for [`GetProjectWorkState::execute`].
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct GetProjectWorkStateInput {
    /// Project whose manifest provides the agent order and boundary.
    pub project: Project,
}

/// Read model for a project's current agent work state.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ProjectWorkState {
    /// Agents in manifest order.
    pub agents: Vec<AgentWorkState>,
    /// Best-effort summaries of the conversations visible through the agents'
    /// tickets, joined frontend-side via `tickets[].conversation_id`. Built from
    /// the [`HandoffStore`] (primary) with a bounded [`ConversationLog`] fallback;
    /// a preview failure never blocks `agents`.
    pub conversations: Vec<ConversationWorkSummary>,
}

/// Best-effort, read-only summary of one conversation visible through the tickets.
///
/// Derived live from the [`HandoffStore`] (primary source) with a bounded
/// [`ConversationLog`] fallback — never a durable projection, never a repair of the
/// underlying log/handoff. Joined frontend-side to tickets via
/// [`ConversationWorkSummary::conversation_id`].
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ConversationWorkSummary {
    /// The conversation (pair) this summary describes.
    pub conversation_id: ConversationId,
    /// How much could be derived (see [`ConversationPreviewStatus`]).
    pub status: ConversationPreviewStatus,
    /// Bounded excerpt of the handoff objective, when present.
    pub objective_preview: Option<String>,
    /// Bounded excerpt of the handoff summary, when a handoff is readable.
    pub summary_preview: Option<String>,
    /// Character length of the **original** (un-truncated) handoff summary (`0` when none).
    pub summary_len: usize,
    /// Cursor (last [`TurnId`]) covered by the handoff summary, when present.
    pub up_to: Option<TurnId>,
    /// Bounded, recent turns from the log fallback (empty when a handoff is `Ready`).
    pub recent_turns: Vec<ConversationTurnWorkPreview>,
}

/// How much of a [`ConversationWorkSummary`] could be derived, best-effort.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ConversationPreviewStatus {
    /// A handoff was present and usable: summary/objective/cursor are filled.
    Ready,
    /// No handoff yet; `recent_turns` carries the log fallback if any.
    Missing,
    /// The handoff was unreadable but the log fallback was readable.
    Partial,
    /// Neither the handoff nor the log could be read.
    Unavailable,
}

/// One recent turn, projected for the conversation-summary fallback.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ConversationTurnWorkPreview {
    /// Nature of the turn (prompt, response, tool activity).
    pub role: TurnRole,
    /// Origin of the turn (human operator or a delegating agent).
    pub source: TicketWorkSource,
    /// Timestamp (epoch milliseconds) of the turn.
    pub at_ms: u64,
    /// Bounded, whitespace-normalised excerpt of the turn text.
    pub text_preview: String,
    /// Character length of the **original** (un-truncated) turn text.
    pub text_len: usize,
}

/// Builds the [`ConversationLog`] bound to a given project `root`, best-effort.
///
/// Twin of [`HandoffProvider`]: the work-state read model is a singleton (the project
/// root arrives per call via [`GetProjectWorkStateInput`]) while the `Fs*` adapters fix
/// their root at construction. This port materialises the log targeting the **right**
/// folder on each call; `None` ⇒ no log fallback (zero regression for call
/// sites/tests that do not wire it). Implemented in `app-tauri` (sole owner of `Fs*`).
pub trait ConversationLogProvider: Send + Sync {
    /// Builds the [`ConversationLog`] whose persistence targets `root`, or `None`.
    fn conversation_log_for(&self, root: &ProjectPath) -> Option<Arc<dyn ConversationLog>>;
}

/// Read model for one manifest agent.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct AgentWorkState {
    /// Agent id.
    pub agent_id: AgentId,
    /// Agent display name.
    pub name: String,
    /// Runtime profile id currently assigned to the agent.
    pub profile_id: ProfileId,
    /// Current live session, if the agent is live.
    pub live: Option<LiveWorkSession>,
    /// Current FIFO/busy state.
    pub busy: AgentBusyState,
    /// Pending/in-progress delegation tickets, in FIFO order.
    pub tickets: Vec<AgentTicketState>,
}

/// One queued delegation ticket, projected for the work-state read model.
///
/// A read-only, presentation-oriented view of a [`QueuedTicketSnapshot`]: the
/// status is **derived** by crossing the FIFO snapshot with the agent's busy state
/// (never stored), and `task_preview` is a bounded excerpt of the full task (the
/// full text is never sent to the panel; `task_len` signals there is more).
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct AgentTicketState {
    /// Stable id of the queued ticket.
    pub ticket_id: TicketId,
    /// Conversation thread this task enters.
    pub conversation_id: ConversationId,
    /// FIFO position at snapshot time (`0` = head).
    pub position: u32,
    /// Derived status (in-progress = the agent's current busy ticket).
    pub status: TicketWorkStatus,
    /// Origin of the ticket (human operator or a delegating agent).
    pub source: TicketWorkSource,
    /// Display label of the requester.
    pub requester_label: String,
    /// Bounded, whitespace-normalised excerpt of the task.
    pub task_preview: String,
    /// Character length of the **original** (un-truncated) task.
    pub task_len: usize,
}

/// Derived processing status of a queued ticket.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum TicketWorkStatus {
    /// The agent's current busy turn is running this ticket.
    InProgress,
    /// Waiting behind the head / the agent is idle.
    Queued,
}

/// Origin of a queued ticket, mirroring [`InputSource`] for the read model.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum TicketWorkSource {
    /// The human operator.
    Human,
    /// Another agent delegating via `idea_ask_agent`.
    Agent {
        /// The delegating agent.
        agent_id: AgentId,
    },
}

impl From<InputSource> for TicketWorkSource {
    fn from(source: InputSource) -> Self {
        match source {
            InputSource::Human => Self::Human,
            InputSource::Agent { agent_id } => Self::Agent { agent_id },
        }
    }
}

/// Live session coordinates exposed by the work-state read model.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct LiveWorkSession {
    /// The layout node currently hosting the session view.
    pub node_id: NodeId,
    /// The live session id.
    pub session_id: SessionId,
    /// Runtime family that owns the session.
    pub kind: LiveSessionKind,
}

/// Read-only use case aggregating manifest agents with live and busy state.
pub struct GetProjectWorkState {
    contexts: Arc<dyn AgentContextStore>,
    live: Arc<LiveSessions>,
    input: Arc<dyn InputMediator>,
    queue: Arc<dyn AgentQueueSnapshot>,
    /// Per-root handoff source (primary), wired best-effort; `None` ⇒ no summaries.
    handoffs: Option<Arc<dyn HandoffProvider>>,
    /// Per-root log source (fallback), wired best-effort; `None` ⇒ no fallback turns.
    logs: Option<Arc<dyn ConversationLogProvider>>,
}

impl GetProjectWorkState {
    /// Builds the read-model use case from existing stores/registries.
    ///
    /// Conversation summaries are off by default; wire them with
    /// [`Self::with_conversation_sources`].
    #[must_use]
    pub fn new(
        contexts: Arc<dyn AgentContextStore>,
        live: Arc<LiveSessions>,
        input: Arc<dyn InputMediator>,
        queue: Arc<dyn AgentQueueSnapshot>,
    ) -> Self {
        Self {
            contexts,
            live,
            input,
            queue,
            handoffs: None,
            logs: None,
        }
    }

    /// Wires the best-effort conversation-summary sources (Lot C): the handoff
    /// store (primary) and the conversation log (bounded fallback), both resolved
    /// per project root. Builder so existing call sites/tests stay unchanged.
    #[must_use]
    pub fn with_conversation_sources(
        mut self,
        handoffs: Arc<dyn HandoffProvider>,
        logs: Arc<dyn ConversationLogProvider>,
    ) -> Self {
        self.handoffs = Some(handoffs);
        self.logs = Some(logs);
        self
    }

    /// Executes the read-only aggregation.
    ///
    /// # Errors
    /// - [`AppError::Store`] when the manifest cannot be loaded,
    /// - [`AppError::Invalid`] if a manifest entry violates agent invariants.
    pub async fn execute(
        &self,
        input: GetProjectWorkStateInput,
    ) -> Result<ProjectWorkState, AppError> {
        let manifest = self.contexts.load_manifest(&input.project).await?;
        let live_by_agent = live_by_agent(self.live.live_agent_snapshots());
        let agents = manifest
            .entries
            .iter()
            .map(|entry| {
                let agent = entry
                    .to_agent()
                    .map_err(|err| AppError::Invalid(err.to_string()))?;
                let live = live_by_agent
                    .get(&agent.id)
                    .map(|snapshot| LiveWorkSession {
                        node_id: snapshot.node_id,
                        session_id: snapshot.session_id,
                        kind: snapshot.kind,
                    });
                // Tickets are crossed with the busy state: only an agent absent from
                // the manifest is dropped (this loop only visits manifest entries), so
                // the manifest boundary is naturally preserved.
                let busy_ticket = self.input.busy_state(agent.id).ticket();
                let tickets = self
                    .queue
                    .queue_for(agent.id)
                    .into_iter()
                    .map(|snapshot| ticket_state(snapshot, busy_ticket))
                    .collect();
                Ok(AgentWorkState {
                    agent_id: agent.id,
                    name: agent.name,
                    profile_id: agent.profile_id,
                    live,
                    busy: self.input.busy_state(agent.id),
                    tickets,
                })
            })
            .collect::<Result<Vec<_>, AppError>>()?;

        // Lot C — best-effort conversation summaries. Only the conversations
        // visible through the projected tickets are summarised, deduplicated in
        // first-seen order. A preview failure degrades the per-conversation status
        // (never an `AppError`): `agents`/live/busy/tickets stay intact above.
        let conversations = self
            .summarise_conversations(&input.project.root, &agents)
            .await;

        Ok(ProjectWorkState {
            agents,
            conversations,
        })
    }

    /// Derives the best-effort summaries of the conversations referenced by the
    /// projected tickets. Resolves the per-root handoff/log stores once, then folds
    /// each distinct conversation id through [`conversation_summary`].
    async fn summarise_conversations(
        &self,
        root: &ProjectPath,
        agents: &[AgentWorkState],
    ) -> Vec<ConversationWorkSummary> {
        let conversation_ids = distinct_conversation_ids(agents);
        if conversation_ids.is_empty() {
            return Vec::new();
        }
        let handoff_store = self
            .handoffs
            .as_ref()
            .and_then(|provider| provider.handoff_store_for(root));
        let log_store = self
            .logs
            .as_ref()
            .and_then(|provider| provider.conversation_log_for(root));

        let mut summaries = Vec::with_capacity(conversation_ids.len());
        for conversation in conversation_ids {
            summaries.push(conversation_summary(conversation, &handoff_store, &log_store).await);
        }
        summaries
    }
}

/// Collects the conversation ids referenced by the agents' tickets, deduplicated in
/// first-seen (FIFO) order so the summary list mirrors the panel's ordering.
fn distinct_conversation_ids(agents: &[AgentWorkState]) -> Vec<ConversationId> {
    let mut seen = HashSet::new();
    let mut ids = Vec::new();
    for agent in agents {
        for ticket in &agent.tickets {
            if seen.insert(ticket.conversation_id) {
                ids.push(ticket.conversation_id);
            }
        }
    }
    ids
}

/// Derives one conversation summary, best-effort, following the Lot C algorithm:
/// handoff present ⇒ `Ready`; absent ⇒ `Missing` (+ log fallback); unreadable but
/// log readable ⇒ `Partial`; both KO ⇒ `Unavailable`. Never returns an error.
async fn conversation_summary(
    conversation: ConversationId,
    handoff_store: &Option<Arc<dyn HandoffStore>>,
    log_store: &Option<Arc<dyn ConversationLog>>,
) -> ConversationWorkSummary {
    // A handoff store absent from the wiring is treated as "no handoff yet"
    // (`Missing` path), never as an error: the read model stays best-effort.
    let handoff = match handoff_store {
        Some(store) => Some(store.load(conversation).await),
        None => None,
    };
    match handoff {
        Some(Ok(Some(handoff))) => ready_summary(conversation, &handoff),
        Some(Ok(None)) | None => {
            // Handoff legitimately absent: status stays Missing even if the log
            // fallback is itself unreadable (then simply no recent turns).
            let recent_turns = recent_turns(log_store, conversation)
                .await
                .unwrap_or_default();
            ConversationWorkSummary {
                conversation_id: conversation,
                status: ConversationPreviewStatus::Missing,
                objective_preview: None,
                summary_preview: None,
                summary_len: 0,
                up_to: None,
                recent_turns,
            }
        }
        Some(Err(_)) => match recent_turns(log_store, conversation).await {
            // Handoff unreadable but the log answered: partial view from the turns.
            Some(recent_turns) => ConversationWorkSummary {
                conversation_id: conversation,
                status: ConversationPreviewStatus::Partial,
                objective_preview: None,
                summary_preview: None,
                summary_len: 0,
                up_to: None,
                recent_turns,
            },
            // Both sources failed: nothing usable to show.
            None => ConversationWorkSummary {
                conversation_id: conversation,
                status: ConversationPreviewStatus::Unavailable,
                objective_preview: None,
                summary_preview: None,
                summary_len: 0,
                up_to: None,
                recent_turns: Vec::new(),
            },
        },
    }
}

/// Projects a readable [`Handoff`] into a `Ready` summary with bounded previews.
fn ready_summary(conversation: ConversationId, handoff: &Handoff) -> ConversationWorkSummary {
    ConversationWorkSummary {
        conversation_id: conversation,
        status: ConversationPreviewStatus::Ready,
        objective_preview: handoff
            .objective
            .as_deref()
            .map(|objective| preview(objective, OBJECTIVE_PREVIEW_MAX_CHARS)),
        summary_preview: Some(preview(&handoff.summary_md, HANDOFF_PREVIEW_MAX_CHARS)),
        summary_len: handoff.summary_md.chars().count(),
        up_to: Some(handoff.up_to),
        recent_turns: Vec::new(),
    }
}

/// Reads the bounded recent-turns fallback for `conversation`.
///
/// Returns `Some(turns)` (possibly empty) when a log store is wired and answers,
/// `None` when there is no log store or the read failed — the caller uses that
/// distinction to separate `Partial` from `Unavailable`. Never reads the full thread
/// (only [`ConversationLog::last`]) and re-caps defensively to [`RECENT_TURNS_MAX`].
async fn recent_turns(
    log_store: &Option<Arc<dyn ConversationLog>>,
    conversation: ConversationId,
) -> Option<Vec<ConversationTurnWorkPreview>> {
    let store = log_store.as_ref()?;
    match store.last(conversation, RECENT_TURNS_MAX).await {
        Ok(turns) => Some(
            turns
                .into_iter()
                .take(RECENT_TURNS_MAX)
                .map(turn_preview)
                .collect(),
        ),
        Err(_) => None,
    }
}

/// Projects one [`ConversationTurn`] into its bounded read-model preview.
fn turn_preview(turn: ConversationTurn) -> ConversationTurnWorkPreview {
    ConversationTurnWorkPreview {
        role: turn.role,
        source: turn.source.into(),
        at_ms: turn.at_ms,
        text_preview: preview(&turn.text, TURN_PREVIEW_MAX_CHARS),
        text_len: turn.text.chars().count(),
    }
}

/// Projects one FIFO snapshot into a read-model ticket, deriving status from the
/// agent's current busy ticket (the one running its turn = `InProgress`).
fn ticket_state(snapshot: QueuedTicketSnapshot, busy_ticket: Option<TicketId>) -> AgentTicketState {
    let status = if busy_ticket == Some(snapshot.id) {
        TicketWorkStatus::InProgress
    } else {
        TicketWorkStatus::Queued
    };
    AgentTicketState {
        ticket_id: snapshot.id,
        conversation_id: snapshot.conversation,
        position: snapshot.position,
        status,
        source: snapshot.source.into(),
        requester_label: snapshot.requester,
        task_preview: task_preview(&snapshot.task),
        task_len: snapshot.task.chars().count(),
    }
}

/// Builds the bounded task excerpt for the UI panel (see [`preview`]).
///
/// The original length is reported separately as [`AgentTicketState::task_len`].
fn task_preview(task: &str) -> String {
    preview(task, TASK_PREVIEW_MAX_CHARS)
}

/// Builds a bounded, whitespace-normalised excerpt of `text` for the UI.
///
/// Trims, collapses any run of whitespace to a single space, then truncates to
/// `max_chars` characters (never mid-codepoint). The original length is reported
/// separately by each caller's `*_len` field.
fn preview(text: &str, max_chars: usize) -> String {
    let normalised = text.split_whitespace().collect::<Vec<_>>().join(" ");
    if normalised.chars().count() <= max_chars {
        normalised
    } else {
        normalised.chars().take(max_chars).collect()
    }
}

fn live_by_agent(snapshots: Vec<LiveSessionSnapshot>) -> HashMap<AgentId, LiveSessionSnapshot> {
    let mut out = HashMap::new();
    for snapshot in snapshots {
        out.entry(snapshot.agent_id).or_insert(snapshot);
    }
    out
}