//! Multi-turn session API (v0.2).
//!
//! v0.2 adds a parallel `/sessions/*` surface to clawdforge backed by ACPX. A
//! [`Session`] is a handle to one server-side session; [`Session::turn`]
//! dispatches a single prompt+files turn and returns the structured event
//! batch. Sessions are explicitly closed via [`Session::close`] (consumes the
//! handle, preventing use-after-close at compile time) or — as a last-resort
//! fallback — best-effort closed by [`Drop`] via `tokio::spawn`.
//!
//! v0.1 single-turn `Client::run` is unchanged; the v0.2 surface is purely
//! additive.

use std::sync::atomic::{AtomicBool, Ordering};

use serde::{Deserialize, Serialize};

use crate::client::Client;
use crate::error::Error;

/// Options passed to [`Client::new_session`].
///
/// `Default` produces `agent = None` (server picks `"claude"`) and `meta =
/// None`.
#[derive(Debug, Default, Clone, Serialize)]
pub struct SessionOptions {
    /// Agent slug to dispatch to. `None` falls back to the server-side default
    /// (`"claude"`).
    #[serde(skip_serializing_if = "Option::is_none")]
    pub agent: Option<String>,

    /// Free-form metadata stored alongside the session ledger row.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub meta: Option<serde_json::Value>,
}

/// Reply body from `POST /sessions`.
#[derive(Debug, Clone, Deserialize)]
pub(crate) struct SessionCreateResponse {
    pub session_id: String,
    pub agent: String,
    pub created_at: i64,
}

/// One event in a turn's structured output.
///
/// `event_type` is one of `"thinking"`, `"text"`, `"tool_call"`, etc. (server
/// is the authority on the set).
#[derive(Debug, Clone, Deserialize, Serialize)]
pub struct TurnEvent {
    /// Event discriminator (`"text"`, `"thinking"`, `"tool_call"`, ...).
    #[serde(rename = "type")]
    pub event_type: String,
    /// Text content for `"text"` and `"thinking"` events.
    #[serde(default)]
    pub content: Option<String>,
    /// Tool name for `"tool_call"` events.
    #[serde(default)]
    pub name: Option<String>,
    /// Tool arguments for `"tool_call"` events.
    #[serde(default)]
    pub args: Option<serde_json::Value>,
    /// Tool result for `"tool_call"` events.
    #[serde(default)]
    pub result: Option<serde_json::Value>,
}

/// Successful response body from `POST /sessions/{id}/turn`.
#[derive(Debug, Clone, Deserialize)]
pub struct TurnResult {
    /// Always `true` on a 200 reply.
    pub ok: bool,
    /// The session this turn belongs to.
    pub session_id: String,
    /// 1-based index of this turn within the session.
    pub turn_index: i32,
    /// Structured events emitted during the turn.
    pub events: Vec<TurnEvent>,
    /// Reason the agent stopped (`"end_turn"`, `"max_tokens"`, ...).
    pub stop_reason: String,
    /// Wall-clock duration of the turn.
    pub duration_ms: i64,
}

impl TurnResult {
    /// Concatenate all `"text"` event contents into a single string.
    ///
    /// Non-text events (`thinking`, `tool_call`, ...) are skipped. If an event
    /// is `"text"` but `content` is `None`, it contributes the empty string.
    pub fn text(&self) -> String {
        let mut out = String::new();
        for ev in &self.events {
            if ev.event_type == "text" {
                if let Some(c) = ev.content.as_deref() {
                    out.push_str(c);
                }
            }
        }
        out
    }
}

/// Reply body from `GET /sessions/{id}` and entries in `GET /sessions`.
#[derive(Debug, Clone, Deserialize, Serialize)]
pub struct SessionState {
    /// Server-issued session id.
    pub session_id: String,
    /// Agent slug bound to the session.
    pub agent: String,
    /// App / consumer name that owns the session.
    pub app_name: String,
    /// Unix epoch seconds when created.
    pub created_at: i64,
    /// Unix epoch seconds of the last successful turn (or `None` if zero turns
    /// have been dispatched yet).
    #[serde(default)]
    pub last_turn_at: Option<i64>,
    /// Number of turns dispatched.
    pub turn_count: i32,
    /// Unix epoch seconds when closed (or `None` if still open).
    #[serde(default)]
    pub closed_at: Option<i64>,
}

/// Reply body from `DELETE /sessions/{id}`.
#[derive(Debug, Clone, Deserialize)]
pub(crate) struct SessionCloseResponse {
    #[allow(dead_code)]
    pub ok: bool,
    #[serde(default)]
    #[allow(dead_code)]
    pub already_closed: Option<bool>,
}

/// Reply body from `GET /sessions`.
#[derive(Debug, Clone, Deserialize, Serialize)]
pub struct SessionList {
    /// All sessions visible to the calling token.
    pub sessions: Vec<SessionState>,
}

/// Request body for `POST /sessions/{id}/turn`.
#[derive(Debug, Serialize)]
struct TurnRequest<'a> {
    prompt: String,
    #[serde(skip_serializing_if = "Option::is_none")]
    files: Option<&'a [String]>,
}

/// A handle to one server-side multi-turn session.
///
/// Construct via [`Client::new_session`]. Drop or [`Session::close`] to
/// release the server-side session. `close` consumes the value so use-after-
/// close is a compile error; `Drop` is a best-effort backstop that fires an
/// async DELETE via `tokio::spawn` and logs (does not panic) on failure.
///
/// `Debug` is hand-written and explicitly excludes the embedded [`Client`] so
/// no bearer can leak through `{:?}` formatting.
pub struct Session {
    pub(crate) client: Client,
    pub(crate) session_id: String,
    pub(crate) agent: String,
    pub(crate) created_at: i64,
    pub(crate) closed: AtomicBool,
}

impl std::fmt::Debug for Session {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        // Deliberately omit `client` — its Debug already redacts tokens, but
        // the spec-mandated shape is `Session { session_id, agent, closed }`
        // to keep the surface minimal and audit-friendly.
        f.debug_struct("Session")
            .field("session_id", &self.session_id)
            .field("agent", &self.agent)
            .field("created_at", &self.created_at)
            .field("closed", &self.closed.load(Ordering::Acquire))
            .finish()
    }
}

impl Session {
    /// Server-issued session id.
    pub fn id(&self) -> &str {
        &self.session_id
    }

    /// Agent slug the server bound to this session.
    pub fn agent(&self) -> &str {
        &self.agent
    }

    /// Unix epoch seconds when the session was created server-side.
    pub fn created_at(&self) -> i64 {
        self.created_at
    }

    /// Whether the session has been explicitly closed already. Sessions closed
    /// only via `Drop`'s spawn are still reported as closed once that future
    /// has run; this getter reflects the in-memory flag.
    pub fn is_closed(&self) -> bool {
        self.closed.load(Ordering::Acquire)
    }

    /// Send a turn with no attached files.
    ///
    /// Equivalent to `turn_with_files(prompt, &[])` but skips serializing the
    /// `files` field on the wire.
    pub async fn turn(&mut self, prompt: impl Into<String>) -> Result<TurnResult, Error> {
        self.dispatch_turn(prompt.into(), None).await
    }

    /// Send a turn that references previously uploaded file tokens.
    ///
    /// `files` is the list of `ff_*` tokens returned by [`Client::upload_file`].
    ///
    /// [`Client::upload_file`]: crate::Client::upload_file
    pub async fn turn_with_files(
        &mut self,
        prompt: impl Into<String>,
        files: &[String],
    ) -> Result<TurnResult, Error> {
        self.dispatch_turn(prompt.into(), Some(files)).await
    }

    async fn dispatch_turn(
        &mut self,
        prompt: String,
        files: Option<&[String]>,
    ) -> Result<TurnResult, Error> {
        if self.closed.load(Ordering::Acquire) {
            return Err(Error::Config("session is closed".into()));
        }
        self.client
            .turn_internal(&self.session_id, &TurnRequest { prompt, files })
            .await
    }

    /// Explicitly close the session. Consumes `self` — use-after-close is a
    /// compile error.
    ///
    /// If the session is already closed in memory (e.g. via a prior failed
    /// close or a prior dispatch path that flagged it), this short-circuits
    /// without contacting the server.
    pub async fn close(self) -> Result<(), Error> {
        // Mark closed before the network call so a panic-mid-await on the
        // request future cannot trigger Drop's spawn into a double-close.
        if self.closed.swap(true, Ordering::AcqRel) {
            return Ok(());
        }
        self.client.close_session_internal(&self.session_id).await
    }
}

impl Drop for Session {
    fn drop(&mut self) {
        // If close() already ran, nothing to do.
        if self.closed.swap(true, Ordering::AcqRel) {
            return;
        }
        // tokio::spawn panics if no runtime is current. Guard against being
        // dropped from a sync context (e.g. a forgotten value at the end of a
        // sync `main`).
        if tokio::runtime::Handle::try_current().is_err() {
            tracing::warn!(
                session_id = %self.session_id,
                "Session dropped outside a tokio runtime; server-side session not closed"
            );
            return;
        }
        let client = self.client.clone();
        let id = self.session_id.clone();
        tokio::spawn(async move {
            if let Err(e) = client.close_session_internal(&id).await {
                tracing::warn!(
                    session_id = %id,
                    error = %e,
                    "best-effort drop close failed"
                );
            }
        });
    }
}