//! Wake-signal writer: notifies the hyperhive harness when an incoming
//! matrix event arrives so claude drives a new turn.
//!
//! Same wire shape as `hive-ag3nt::forge_notify`'s wake: a single JSON
//! line written to the hyperhive control socket (`/run/hive/mcp.sock`
//! by default) carrying an `AgentRequest::Wake { from, body }`.
//! The agent harness's `agent_server` parses it and treats it as a
//! `Wake` from the matrix subsystem.
//!
//! Per the operator's call (phase 3): the body is a SHORT TEASER, not
//! the full message — the agent then reads the unmarked event via
//! the `read_room` MCP tool. Truncation to ~100 chars keeps the wake
//! prompt focused (`forge_notify` embeds longer excerpts because the
//! agent doesn't have a follow-up read-the-original tool for forge).

use std::path::Path;

use anyhow::{Context, Result};
use tokio::io::AsyncWriteExt;
use tokio::net::UnixStream;

/// Max characters of `body` to embed in the wake payload. Shorter than
/// `forge_notify`'s 500-byte excerpt because the agent has a follow-up
/// `read_room` tool to fetch the full event.
pub const WAKE_BODY_TRUNCATE: usize = 100;

/// Send an `AgentRequest::Wake { from: "matrix", body }` to the hyperhive
/// control socket at `socket`. Best-effort: returns Err on any plumbing
/// failure; callers log + ignore so a wake delivery hiccup doesn't tear
/// down the matrix sync loop.
///
/// Wire format matches `hive_sh4re::Request` tagged with `"cmd"` per
/// `#[serde(tag = "cmd", rename_all = "snake_case")]`.  Must be `"cmd"`,
/// not `"kind"` — the harness deserialises against the hive-sh4re type
/// and silently discards requests that don't match.
///
/// # Errors
///
/// Returns an error on socket connect failure, serialisation failure,
/// or I/O error writing to or reading from the socket.
pub async fn send_wake(socket: &Path, body: impl AsRef<str>) -> Result<()> {
    use tokio::io::AsyncBufReadExt;

    let payload = serde_json::json!({
        "cmd": "wake",
        "from": "matrix",
        "body": body.as_ref(),
        "transient": true,
    });
    let line = format!("{}\n", serde_json::to_string(&payload)?);
    let stream = UnixStream::connect(socket)
        .await
        .with_context(|| format!("connect hyperhive socket {}", socket.display()))?;
    let (read, mut write) = stream.into_split();
    write
        .write_all(line.as_bytes())
        .await
        .with_context(|| format!("write wake to {}", socket.display()))?;
    write
        .shutdown()
        .await
        .with_context(|| format!("shutdown write to {}", socket.display()))?;
    // Drain the response line so the server doesn't get ECONNRESET on
    // its write-back.  We don't act on the response — best-effort wake.
    let mut reader = tokio::io::BufReader::new(read);
    let mut resp = String::new();
    let _ = reader.read_line(&mut resp).await;
    Ok(())
}

/// Format a wake-message body from a matrix event's sender + room
/// canonical alias + body text. Truncates at [`WAKE_BODY_TRUNCATE`]
/// chars with an ellipsis. Shape: `[matrix] <sender> in <room>: <text>`
/// matches the `forge_notify` `[issue …]` framing convention.
#[must_use]
pub fn format_wake_body(sender: &str, room: &str, text: &str) -> String {
    let truncated = truncate_chars(text, WAKE_BODY_TRUNCATE);
    format!("[matrix] {sender} in {room}: {truncated}")
}

/// Format a wake-message body from a list of per-room unread summaries.
/// Single-room / single-message case collapses to the terse one-liner
/// format; multiple rooms expand to a bulleted list. Always appends a
/// read-hint line so the agent knows which tools to reach for.
#[must_use]
pub fn format_unread_summary(rooms: &[crate::protocol::RoomUnread]) -> String {
    use std::fmt::Write as _;
    if rooms.is_empty() {
        return String::new();
    }
    // Terse path: exactly one room, exactly one unread with body.
    if rooms.len() == 1 {
        let r = &rooms[0];
        if r.count == 1
            && let (Some(body), Some(sender)) = (&r.last_body, &r.last_sender)
        {
            return format!(
                "[matrix] {sender} in {label}: {body} — use read_room to view, mark_read to clear",
                label = r.label
            );
        }
        return format!(
            "[matrix] {} unread in {} — use read_room to view, mark_read to clear",
            r.count, r.label
        );
    }
    // Multi-room path.
    let mut out = String::from("[matrix] unread messages:");
    for r in rooms {
        if r.count == 1
            && let (Some(body), Some(sender)) = (&r.last_body, &r.last_sender)
        {
            let _ = write!(out, "\n- {}: {sender}: {body}", r.label);
            continue;
        }
        let _ = write!(out, "\n- {}: {} unread", r.label, r.count);
    }
    out.push_str("\nUse list_rooms + read_room to view, mark_read to clear.");
    out
}

/// Prepend an account marker to a wake `body` when the daemon serves
/// more than one matrix account. `tag` is `Some(name)` only in
/// multi-account mode; `None` returns `body` unchanged so single-account
/// wakes keep their exact format. Shape: `[acct:<name>] <body>`.
#[must_use]
pub fn tag_account(tag: Option<&str>, body: String) -> String {
    match tag {
        Some(name) => format!("[acct:{name}] {body}"),
        None => body,
    }
}

/// Truncate `s` to `max` Unicode chars, appending `…` when cut.
/// Char-based not byte-based so multi-byte content (most chat) doesn't
/// get cut mid-codepoint.
#[must_use]
pub fn truncate_chars(s: &str, max: usize) -> String {
    let mut end = s.len();
    for (count, (i, _)) in s.char_indices().enumerate() {
        if count == max {
            end = i;
            break;
        }
    }
    if end == s.len() {
        s.to_owned()
    } else {
        format!("{}…", &s[..end])
    }
}

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

    #[test]
    fn format_wake_body_short_passes_through() {
        let body = format_wake_body("@iris:matrix.darkest.space", "#general", "hi all");
        assert_eq!(
            body,
            "[matrix] @iris:matrix.darkest.space in #general: hi all"
        );
    }

    #[test]
    fn format_wake_body_long_truncates_with_ellipsis() {
        let long = "x".repeat(200);
        let body = format_wake_body("@iris:m", "#x", &long);
        assert!(body.contains("xxxxxxx"));
        assert!(body.ends_with("…"));
        // Header + truncated body should be well under the absolute
        // wake-message ceiling (forge_notify uses ~600 bytes; we're
        // way under that).
        assert!(body.len() < 200);
    }

    #[test]
    fn truncate_chars_handles_multibyte() {
        // `ü` is 2 bytes / 1 char. truncating to 3 chars on "üüüüüü"
        // should yield "üüü…" not "üü\xc3…" (mid-codepoint).
        let s = "üüüüüü";
        let t = truncate_chars(s, 3);
        assert_eq!(t, "üüü…");
    }

    #[test]
    fn truncate_chars_no_op_below_limit() {
        let s = "hi";
        assert_eq!(truncate_chars(s, 100), "hi");
    }

    #[test]
    fn tag_account_none_is_passthrough() {
        let body = "[matrix] @a:s in #x: hi".to_owned();
        assert_eq!(tag_account(None, body.clone()), body);
    }

    #[test]
    fn tag_account_some_prepends_marker() {
        let body = "[matrix] @a:s in #x: hi".to_owned();
        assert_eq!(
            tag_account(Some("ccc"), body),
            "[acct:ccc] [matrix] @a:s in #x: hi"
        );
    }
}