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// SPDX-FileCopyrightText: 2026 Andrei G <bug-ops>
// SPDX-License-Identifier: MIT OR Apache-2.0
//! Resume-visibility presentation primitive (spec-068 §13).
//!
//! [`SessionResumeInfo`] is computed once at hydration time from the already-reconstructed
//! message stream (`ReplayEngine::fold`'s output, or the `SQLite` fallback when
//! `[session] enabled = false`) and rendered per-channel: a neutral banner on CLI/TUI
//! (display-owning channels), nothing on chat/ACP channels (spec-068 §13.2, §13.8).
//!
//! This module adds zero I/O: it only inspects a message slice already materialized by the
//! caller's hydration path.
use zeph_llm::provider::{Message, Role};
/// Presentation-only summary of a conversation-session's prior state, computed at hydration.
///
/// Carries no full message vector — expansion is pulled lazily by `/history`, never eagerly
/// (spec-068 §13.3).
#[derive(Debug, Clone)]
pub struct SessionResumeInfo {
/// Whether this hydration reconstructed a non-empty prior conversation (§13.4).
pub is_resume: bool,
/// Count of non-system messages in the reconstructed stream.
pub prior_message_count: usize,
/// Approximate number of turns (count of user messages in the reconstructed stream).
pub prior_turn_count: usize,
/// Last-active timestamp, formatted for display (e.g. `"2h ago"`), when known.
pub last_active: Option<String>,
}
impl SessionResumeInfo {
/// Compute resume info from an already-reconstructed message stream.
///
/// `is_resume` is evaluated against the raw message stream — at least one non-system
/// message (`User`, `Assistant`, or a tool-bearing message) makes this `true`, even when
/// the only assistant message is tool-use-only with no visible text (spec-068 §13.4,
/// AC-17). This must never be computed against a display-filtered/visible-text-only turn
/// count — that would false-negative a session interrupted mid-tool-loop as fresh.
///
/// # Examples
///
/// ```
/// use zeph_core::session_resume::SessionResumeInfo;
/// use zeph_llm::provider::{Message, Role};
///
/// let messages = vec![Message::from_legacy(Role::System, "system prompt")];
/// let info = SessionResumeInfo::from_messages(&messages, None);
/// assert!(!info.is_resume, "system-prompt-only history is fresh, not a resume");
/// ```
#[must_use]
pub fn from_messages(messages: &[Message], last_active_raw: Option<&str>) -> Self {
let non_system: Vec<&Message> =
messages.iter().filter(|m| m.role != Role::System).collect();
let prior_turn_count = non_system.iter().filter(|m| m.role == Role::User).count();
Self {
is_resume: !non_system.is_empty(),
prior_message_count: non_system.len(),
prior_turn_count,
last_active: last_active_raw.and_then(format_last_active),
}
}
/// Render the neutral CLI/TUI banner line (spec-068 §13.5).
///
/// Carries no interrupted/clean-exit qualifier in v1 (§13.10). Returns `None` when
/// `is_resume` is `false` — callers must not render anything for a fresh conversation
/// (AC-16).
#[must_use]
pub fn banner_text(&self) -> Option<String> {
if !self.is_resume {
return None;
}
let turns = if self.prior_turn_count == 1 {
"1 turn".to_owned()
} else {
format!("{} turns", self.prior_turn_count)
};
let messages = if self.prior_message_count == 1 {
"1 message".to_owned()
} else {
format!("{} messages", self.prior_message_count)
};
Some(match &self.last_active {
Some(last_active) => format!(
"\u{21bb} Resuming session (last active {last_active}) — {messages}, {turns}. Type /history to view."
),
None => {
format!("\u{21bb} Resuming session — {messages}, {turns}. Type /history to view.")
}
})
}
}
/// Format a `SQLite`/`PostgreSQL` `updated_at` string (`"YYYY-MM-DD HH:MM:SS"`, UTC) as a
/// coarse relative-time string (e.g. `"2h ago"`). Returns `None` if the string cannot be
/// parsed rather than surfacing a raw, potentially confusing timestamp.
fn format_last_active(raw: &str) -> Option<String> {
let parsed = chrono::NaiveDateTime::parse_from_str(raw.trim(), "%Y-%m-%d %H:%M:%S")
.or_else(|_| chrono::NaiveDateTime::parse_from_str(raw.trim(), "%Y-%m-%dT%H:%M:%S%.f"))
.ok()?;
let then = parsed.and_utc();
let now = chrono::Utc::now();
let secs = now.signed_duration_since(then).num_seconds().max(0);
Some(if secs < 60 {
"just now".to_owned()
} else if secs < 3600 {
format!("{}m ago", secs / 60)
} else if secs < 86400 {
format!("{}h ago", secs / 3600)
} else {
format!("{}d ago", secs / 86400)
})
}
#[cfg(test)]
mod tests {
use super::*;
use zeph_llm::provider::MessagePart;
fn msg(role: Role, content: &str) -> Message {
Message::from_legacy(role, content)
}
#[test]
fn fresh_conversation_system_only_is_not_resume() {
let messages = vec![msg(Role::System, "system prompt")];
let info = SessionResumeInfo::from_messages(&messages, None);
assert!(!info.is_resume);
assert_eq!(info.prior_message_count, 0);
assert!(info.banner_text().is_none());
}
#[test]
fn normal_conversation_is_resume() {
let messages = vec![
msg(Role::System, "system prompt"),
msg(Role::User, "hello"),
msg(Role::Assistant, "hi there"),
];
let info = SessionResumeInfo::from_messages(&messages, None);
assert!(info.is_resume);
assert_eq!(info.prior_message_count, 2);
assert_eq!(info.prior_turn_count, 1);
assert!(info.banner_text().unwrap().contains("Resuming session"));
}
/// Regression test for the M-REV2-2 predicate fix (spec-068 §13.4, AC-17): a session
/// interrupted mid-tool-loop reconstructs to `[system, assistant(tool_use-only),
/// user(tool_result)]` — no assistant text — and must still evaluate `is_resume = true`.
#[test]
fn mid_tool_loop_interruption_is_still_resume() {
let mut tool_use_only = msg(Role::Assistant, "");
tool_use_only.parts.push(MessagePart::ToolUse {
id: "toolu_1".to_owned(),
name: "bash".to_owned(),
input: serde_json::json!({"command": "ls"}),
});
let mut tool_result = msg(Role::User, "");
tool_result.parts.push(MessagePart::ToolResult {
tool_use_id: "toolu_1".to_owned(),
content: "file.txt".to_owned(),
is_error: false,
});
let messages = vec![
msg(Role::System, "system prompt"),
tool_use_only,
tool_result,
];
let info = SessionResumeInfo::from_messages(&messages, None);
assert!(
info.is_resume,
"mid-tool-loop interruption must evaluate as resume, not fresh"
);
assert_eq!(info.prior_message_count, 2);
}
#[test]
fn last_active_formats_recent_seconds_as_just_now() {
let now = chrono::Utc::now().format("%Y-%m-%d %H:%M:%S").to_string();
let formatted = format_last_active(&now).expect("must parse");
assert_eq!(formatted, "just now");
}
#[test]
fn last_active_unparsable_returns_none() {
assert!(format_last_active("not-a-date").is_none());
}
#[test]
fn banner_singular_turn_and_message_grammar() {
let messages = vec![msg(Role::System, "sp"), msg(Role::User, "hi")];
let info = SessionResumeInfo::from_messages(&messages, None);
let text = info.banner_text().unwrap();
assert!(text.contains("1 message"));
assert!(text.contains("1 turn"));
assert!(!text.contains("1 turns"));
}
}