//! Honcho's HTTP surface, mounted by the main `WebFrontend` under
//! `/api/plugin/honcho/` behind Skald's normal auth + enabled-gate.
//!
//! Deliberately small. It serves the two page fragments (the admin config page
//! and the user opt-in page) and:
//!
//! - `POST /admin/test` — admin connectivity check against a candidate config.
//! - `GET  /status`     — user-facing service health (reachability + the
//!   caller's own processing queue).
//! - `GET  /overview`   — the caller's full memory snapshot (peer card +
//!   representation digest + derived conclusions with ids). Cheap, no LLM.
//! - `POST /search`     — semantic search over the caller's derived facts.
//! - `POST /ask`        — Dialectic: Honcho's server-side LLM answers a
//!   natural-language question from the caller's memory.
//!
//! The opt-in toggle and the config save reuse the **core** plugin endpoints
//! (`PUT /api/plugins/honcho` and `/api/plugins/honcho/my-config`), so nothing
//! about persistence lives here.
//!
//! # Multi-user boundary (the workspace is shared)
//!
//! Every introspection handler derives the Honcho peer from the authenticated
//! [`Caller`]'s user id via [`require_peer`] — never from the request body —
//! and the workspace id from server config. A client can therefore never name
//! another user's peer, and a bug in a handler can't either: the peer id is
//! handed to the handler already resolved.
//!
//! # Error reporting
//!
//! This page exists to *debug* the integration, so errors are specific, not
//! "service unavailable": transport failures and Honcho HTTP errors are
//! localized with the real detail forwarded (see [`honcho_error`] — the body is
//! truncated, not swallowed). The one status code that is *not* an error is
//! Honcho's 404: for a just-opted-in user with no traffic yet it means "no
//! memory about you yet", and each handler translates it accordingly.
//!
//! Honcho does **not** `manages_own_access`, so — unlike mobile-connector — the
//! `plugin_access` grant is *not* an admin check (it is `true` for every granted
//! user). The admin endpoint therefore gates on the real
//! [`UserChannelApi::is_admin`]; the introspection endpoints gate on the
//! per-user **opt-in** flag instead (fail closed, like the tools).
//!
//! Every request resolves the *current* wiring through the shared [`WebCell`]
//! (filled on `start`, cleared on `stop`), so a reconfigure is transparent and a
//! request that arrives while the plugin is enabled-but-not-running gets a clean
//! 503 rather than a stale snapshot.

use std::sync::Arc;
use std::time::Instant;

use axum::extract::{Extension, State};
use axum::http::{header, StatusCode};
use axum::response::{IntoResponse, Response};
use axum::routing::{get, post};
use axum::{Json, Router};
use serde::Deserialize;
use serde_json::{json, Value};
use tracing::debug;

use core_api::i18n::I18nApi;
use core_api::plugin::Caller;
use core_api::user_channel::UserChannelApi;
use core_api::user_plugin_config::PluginUserConfigApi;
use honcho_client::HonchoClient;
use honcho_client::error::HonchoError;
use honcho_client::models::{
    ConclusionGet, ConclusionQuery, DialecticOptions, PageParams, PeerRepresentationGet,
    WorkspaceGet,
};

// Namespaced i18n keys for the router's user-facing strings (backend tables in
// `../i18n/*.json`), resolved to the caller's language via `web.i18n`.
const KEY_ADMIN_ONLY:       &str = "plugin.honcho.err.admin_only";
const KEY_BASE_URL_EMPTY:   &str = "plugin.honcho.err.base_url_empty";
const KEY_TEST_FAILED:      &str = "plugin.honcho.err.test_failed";
const KEY_NOT_OPTED_IN:     &str = "plugin.honcho.err.not_opted_in";
const KEY_QUERY_REQUIRED:   &str = "plugin.honcho.err.query_required";
const KEY_HONCHO_UNREACHABLE: &str = "plugin.honcho.err.honcho_unreachable";
const KEY_HONCHO_ERROR:     &str = "plugin.honcho.err.honcho_error";
const KEY_NO_DATA:          &str = "plugin.honcho.err.no_data";

/// Max characters of a Honcho error body forwarded to the user — enough to stay
/// specific, short enough not to flood the page with a server stack dump.
const ERR_DETAIL_MAX: usize = 300;

/// Conclusions shown in the overview snapshot (the debug page wants more than
/// the read-path's token-budgeted subset).
const OVERVIEW_MAX_CONCLUSIONS: u32 = 50;
/// Facts returned by `/search` (ranked, raw excerpts).
const SEARCH_TOP_K: u32 = 20;

/// Deps the router needs at request time.
#[derive(Clone)]
pub struct HonchoWeb {
    pub user_channel: Arc<dyn UserChannelApi>,
    pub i18n:         Arc<dyn I18nApi>,
    /// Live Honcho client — the same one the memory read/write paths use.
    pub client:       Arc<HonchoClient>,
    /// The instance's shared workspace id, from server config.
    pub workspace_id: String,
    /// Per-user opt-in store; gates every introspection endpoint.
    pub user_config:  Arc<dyn PluginUserConfigApi>,
}

/// Shared cell: an `Arc` to a `Mutex` holding the (optional) live wiring. Cloned
/// cheaply and shared between the plugin (`start`/`stop`) and the router.
pub type WebCell = Arc<tokio::sync::Mutex<Option<HonchoWeb>>>;

/// Build the plugin's router. Takes the shared cell so each request resolves the
/// *current* wiring — not a snapshot from startup.
pub fn build(cell: WebCell) -> Router {
    Router::new()
        // Page fragments (served as ES modules to the browser).
        .route("/web/config.js", get(|| async { serve_js(include_str!("../web/config.js")) }))
        .route("/web/memory.js", get(|| async { serve_js(include_str!("../web/memory.js")) }))
        .route("/web/common.js", get(|| async { serve_js(include_str!("../web/common.js")) }))
        .route("/web/i18n.js",   get(|| async { serve_js(include_str!("../web/i18n.js")) }))
        // Admin: validate a candidate connection before saving it.
        .route("/admin/test", post(admin_test))
        // User-facing introspection (all gated on the per-user opt-in).
        .route("/status",    get(user_status))
        .route("/overview", get(user_overview))
        .route("/search",   post(user_search))
        .route("/ask",      post(user_ask))
        .with_state(cell)
}

fn serve_js(body: &'static str) -> Response {
    ([(header::CONTENT_TYPE, "text/javascript; charset=utf-8")], body).into_response()
}

/// Resolve the live wiring, or `503` while the plugin is enabled but not running.
async fn web_or_503(cell: &WebCell) -> Result<HonchoWeb, Response> {
    cell.lock().await.clone().ok_or_else(|| {
        (StatusCode::SERVICE_UNAVAILABLE, "honcho is not running").into_response()
    })
}

/// Fail-closed admin gate for the built-in admin role.
async fn require_admin(web: &HonchoWeb, caller: &Caller) -> Result<(), Response> {
    if web.user_channel.is_admin(&caller.user_id).await {
        Ok(())
    } else {
        let msg = web.i18n.for_user(&caller.user_id, KEY_ADMIN_ONLY, &[]).await;
        Err((StatusCode::FORBIDDEN, msg).into_response())
    }
}

/// The opt-in gate for every introspection endpoint — same privacy control as
/// the tools and the write path, resolved server-side, fail closed.
///
/// Returns the **caller's** peer id: in the shared workspace the peer id *is*
/// the multi-user boundary, so it is derived here, from the authenticated user,
/// and handed to the handler already resolved — a client-supplied peer can never
/// reach Honcho.
async fn require_peer(web: &HonchoWeb, caller: &Caller) -> Result<String, Response> {
    if crate::opted_in(&web.user_config, &caller.user_id).await {
        Ok(caller.user_id.clone())
    } else {
        let msg = web.i18n.for_user(&caller.user_id, KEY_NOT_OPTED_IN, &[]).await;
        Err((StatusCode::FORBIDDEN, msg).into_response())
    }
}

/// Localized, *specific* message for a Honcho failure — transport cause or HTTP
/// status + body — because "service unavailable" is exactly what this page must
/// not say. Shared by the JSON-200 `/status` (message only) and the error
/// responses of the other handlers.
async fn honcho_error_text(web: &HonchoWeb, caller: &Caller, e: &HonchoError) -> String {
    match e {
        HonchoError::Http { status, body } => web.i18n
            .for_user(&caller.user_id, KEY_HONCHO_ERROR, &[
                ("status", &status.to_string()),
                ("detail", &truncate_detail(body)),
            ])
            .await,
        // `Request`'s Display walks the whole source chain, so the real cause
        // ("connection refused", "dns error", …) is already in here.
        e @ (HonchoError::Request(_) | HonchoError::Json(_)) => web.i18n
            .for_user(&caller.user_id, KEY_HONCHO_UNREACHABLE, &[("detail", &e.to_string())])
            .await,
    }
}

/// Error response built from [`honcho_error_text`]. 502: the failure happened
/// on the Honcho side, not in this handler.
async fn honcho_error(web: &HonchoWeb, caller: &Caller, e: &HonchoError) -> Response {
    (StatusCode::BAD_GATEWAY, honcho_error_text(web, caller, e).await).into_response()
}

/// Char-boundary-safe truncation of an error body for display.
fn truncate_detail(s: &str) -> String {
    if s.len() <= ERR_DETAIL_MAX {
        return s.to_string();
    }
    let mut end = ERR_DETAIL_MAX;
    while !s.is_char_boundary(end) {
        end -= 1;
    }
    format!("{}…", &s[..end])
}

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

    #[test]
    fn truncate_keeps_short_bodies_intact() {
        assert_eq!(truncate_detail("boom"), "boom");
        // Exactly at the limit is kept whole; one over is cut at the limit.
        assert_eq!(truncate_detail(&"x".repeat(300)), "x".repeat(300));
        assert_eq!(truncate_detail(&"x".repeat(301)), format!("{}…", "x".repeat(300)));
    }

    #[test]
    fn truncate_never_lands_inside_a_multibyte_char() {
        // 300 'è' = 600 bytes: a naive byte cut at 300 would split a codepoint,
        // but byte 300 happens to fall on a boundary — the cut is 150 whole
        // chars plus the ellipsis.
        let long = "è".repeat(300);
        let out = truncate_detail(&long);
        assert!(out.ends_with('…'));
        assert!(out.chars().all(|c| c == 'è' || c == '…'));
        assert_eq!(out.chars().count(), 151);
    }
}

/// Body of `/search` and `/ask`.
#[derive(Deserialize)]
struct QueryBody {
    #[serde(default)]
    query: String,
}

/// Reject an empty/whitespace query with a localized 400.
async fn require_query(web: &HonchoWeb, caller: &Caller, body: &QueryBody) -> Result<String, Response> {
    let q = body.query.trim();
    if q.is_empty() {
        let msg = web.i18n.for_user(&caller.user_id, KEY_QUERY_REQUIRED, &[]).await;
        Err((StatusCode::BAD_REQUEST, msg).into_response())
    } else {
        Ok(q.to_string())
    }
}

// ── POST /admin/test ──────────────────────────────────────────────────────────

#[derive(Deserialize)]
struct TestBody {
    #[serde(default)]
    base_url: String,
    #[serde(default)]
    api_key:  String,
}

/// Admin connectivity check against a *candidate* config (the unsaved draft), so
/// an admin can validate a URL/key before saving. Builds a throwaway client and
/// lists workspaces — verifies the URL is reachable and the key is accepted
/// without creating or mutating anything on the server.
async fn admin_test(
    State(cell):       State<WebCell>,
    Extension(caller): Extension<Caller>,
    Json(body):        Json<TestBody>,
) -> Response {
    let web = match web_or_503(&cell).await {
        Ok(w)  => w,
        Err(r) => return r,
    };
    if let Err(r) = require_admin(&web, &caller).await {
        return r;
    }

    let base_url = body.base_url.trim();
    if base_url.is_empty() {
        let msg = web.i18n.for_user(&caller.user_id, KEY_BASE_URL_EMPTY, &[]).await;
        return (StatusCode::BAD_REQUEST, msg).into_response();
    }

    let client = HonchoClient::with_base_url(base_url, body.api_key.trim());
    match client
        .list_workspaces(&PageParams::default(), &WorkspaceGet::default())
        .await
    {
        Ok(page) => Json(json!({ "ok": true, "workspaces": page.total })).into_response(),
        Err(e) => {
            let msg = web
                .i18n
                .for_user(&caller.user_id, KEY_TEST_FAILED, &[("detail", &e.to_string())])
                .await;
            (StatusCode::BAD_GATEWAY, msg).into_response()
        }
    }
}

// ── GET /status ───────────────────────────────────────────────────────────────

/// Service health for the debug panel: one cheap GET (`queue/status`) that
/// proves the server is reachable, the key is accepted and the workspace
/// exists, plus the caller's own processing queue and the round-trip latency.
///
/// Scoped to the caller's observer id — the workspace is shared, and one user's
/// page must not surface the whole instance's queue.
///
/// Failures are reported as `{ ok: false, error }` with HTTP 200: the *endpoint*
/// worked, and the badge needs the specific message rather than an exception.
async fn user_status(
    State(cell):       State<WebCell>,
    Extension(caller): Extension<Caller>,
) -> Response {
    let web = match web_or_503(&cell).await {
        Ok(w)  => w,
        Err(r) => return r,
    };
    let peer = match require_peer(&web, &caller).await {
        Ok(p)  => p,
        Err(r) => return r,
    };

    let started = Instant::now();
    match web.client.queue_status(&web.workspace_id, Some(&peer), None, None).await {
        Ok(q) => Json(json!({
            "ok":         true,
            "latency_ms": started.elapsed().as_millis() as u64,
            "queue": {
                "pending":     q.pending_work_units,
                "in_progress": q.in_progress_work_units,
                "completed":   q.completed_work_units,
            },
        })).into_response(),
        Err(e) => Json(json!({
            "ok":    false,
            "error": honcho_error_text(&web, &caller, &e).await,
        })).into_response(),
    }
}

// ── GET /overview ─────────────────────────────────────────────────────────────

/// The caller's full memory snapshot — the direct answer to "what does Honcho
/// know about me?": the peer card (curated key facts), the pre-rendered
/// markdown `representation` (what the assistant actually receives), and the
/// individual conclusions with their ids (for targeted deletion). Cheap, no
/// LLM synthesis.
///
/// Schema note (Honcho 3.0.x): `peer_context` carries `representation` +
/// `peer_card`, NOT a `conclusions` array — the ids come from a separate
/// `conclusions/list` scoped to the caller's peer.
async fn user_overview(
    State(cell):       State<WebCell>,
    Extension(caller): Extension<Caller>,
) -> Response {
    let web = match web_or_503(&cell).await {
        Ok(w)  => w,
        Err(r) => return r,
    };
    let peer = match require_peer(&web, &caller).await {
        Ok(p)  => p,
        Err(r) => return r,
    };

    // A 404 on the context call is "no peer yet", not a failure — the peer is
    // created lazily by the write path on the user's first forwarded turn.
    // The card response wraps the list: `{"peer_card": [...] | null}` — unwrap
    // it so the page receives the bare value.
    let card = match web.client.get_peer_card(&web.workspace_id, &peer, None).await {
        Ok(c)  => json!(c.peer_card),
        Err(e @ HonchoError::Http { status: 404, .. }) => {
            debug!("honcho /overview: no card for peer '{peer}' yet: {e}");
            Value::Null
        }
        Err(e) => return honcho_error(&web, &caller, &e).await,
    };

    let representation = match web.client.peer_context(
        &web.workspace_id,
        &peer,
        &PeerRepresentationGet {
            max_conclusions: Some(OVERVIEW_MAX_CONCLUSIONS),
            ..Default::default()
        },
    ).await {
        Ok(ctx) => ctx.representation,
        Err(e @ HonchoError::Http { status: 404, .. }) => {
            debug!("honcho /overview: no context for peer '{peer}' yet: {e}");
            None
        }
        Err(e) => return honcho_error(&web, &caller, &e).await,
    };

    let conclusions = match web.client.list_conclusions(
        &web.workspace_id,
        &PageParams { size: Some(OVERVIEW_MAX_CONCLUSIONS as u64), ..Default::default() },
        &ConclusionGet {
            filters: Some(json!({ "observer_id": peer, "observed_id": peer })),
        },
    ).await {
        Ok(page) => page.items,
        Err(e) => return honcho_error(&web, &caller, &e).await,
    };

    Json(json!({
        "card":           card,
        "representation": representation,
        "conclusions":    conclusions,
    })).into_response()
}

// ── POST /search ──────────────────────────────────────────────────────────────

/// Semantic search over the caller's derived facts: `conclusions/query`,
/// ranked raw excerpts with their ids — no LLM synthesis. The same path as the
/// `honcho_search` tool; the observer/observed scoping lives in `filters`
/// (and `peer_context` would not do: it returns the whole representation with
/// no ids once it fits the budget).
async fn user_search(
    State(cell):       State<WebCell>,
    Extension(caller): Extension<Caller>,
    Json(body):        Json<QueryBody>,
) -> Response {
    let web = match web_or_503(&cell).await {
        Ok(w)  => w,
        Err(r) => return r,
    };
    let peer = match require_peer(&web, &caller).await {
        Ok(p)  => p,
        Err(r) => return r,
    };
    let query = match require_query(&web, &caller, &body).await {
        Ok(q)  => q,
        Err(r) => return r,
    };

    match web.client.query_conclusions(
        &web.workspace_id,
        &ConclusionQuery {
            query,
            top_k:    Some(SEARCH_TOP_K),
            distance: None,
            filters:  Some(json!({ "observer_id": peer, "observed_id": peer })),
        },
    ).await {
        Ok(conclusions) => Json(json!({ "conclusions": conclusions })).into_response(),
        Err(e) => honcho_error(&web, &caller, &e).await,
    }
}

// ── POST /ask ─────────────────────────────────────────────────────────────────

/// Dialectic query: Honcho's **server-side** LLM reads the caller's memory and
/// synthesizes an answer in natural language. Slower and costlier than
/// `/search` (an LLM round-trip inside Honcho) — that is why it is a separate
/// action in the UI, and why it runs at `reasoning_level: low`.
async fn user_ask(
    State(cell):       State<WebCell>,
    Extension(caller): Extension<Caller>,
    Json(body):        Json<QueryBody>,
) -> Response {
    let web = match web_or_503(&cell).await {
        Ok(w)  => w,
        Err(r) => return r,
    };
    let peer = match require_peer(&web, &caller).await {
        Ok(p)  => p,
        Err(r) => return r,
    };
    let query = match require_query(&web, &caller, &body).await {
        Ok(q)  => q,
        Err(r) => return r,
    };

    let opts = DialecticOptions {
        query,
        session_id:      None,
        target:          None,
        stream:          Some(false),
        reasoning_level: Some("low".to_string()),
    };
    match web.client.peer_chat(&web.workspace_id, &peer, &opts).await {
        Ok(response) => {
            // Same extraction as the `memory_query` tool: known content fields,
            // falling back to pretty-printed JSON so nothing is ever hidden.
            let answer = response.get("content")
                .or_else(|| response.get("response"))
                .or_else(|| response.get("message"))
                .and_then(Value::as_str)
                .map(str::to_string)
                .unwrap_or_else(|| {
                    serde_json::to_string_pretty(&response)
                        .unwrap_or_else(|_| response.to_string())
                });
            Json(json!({ "answer": answer })).into_response()
        }
        // No peer in Honcho yet: not an error — answer with the localized
        // "no memory yet" line so it reads naturally in the panel.
        Err(e @ HonchoError::Http { status: 404, .. }) => {
            debug!("honcho /ask: no peer '{peer}' yet: {e}");
            let msg = web.i18n.for_user(&caller.user_id, KEY_NO_DATA, &[]).await;
            Json(json!({ "answer": msg })).into_response()
        }
        Err(e) => honcho_error(&web, &caller, &e).await,
    }
}