agent-harness 0.4.0-alpha.3

//! Translate ACP `session/update` notifications into the neutral
//! [`crate::RunEvent`] stream — the payoff of aligning `RunEvent`'s schema to
//! ACP's `SessionUpdate` (so this mapping is near 1:1 and lossless).
//!
//! Pure (no async, no I/O), so it's unit-tested without a live ACP agent.

use agent_client_protocol::schema as acp;

use crate::{PlanEntry, PlanEntryPriority, PlanEntryStatus, RunEvent, ToolKind, ToolLocation};

/// One ACP `SessionUpdate` → zero or more `RunEvent`s for `run_id`.
pub(crate) fn session_update_to_events(run_id: &str, update: acp::SessionUpdate) -> Vec<RunEvent> {
    let rid = || run_id.to_owned();
    match update {
        // Streamed assistant text / reasoning — the exact-match cases.
        acp::SessionUpdate::AgentMessageChunk(chunk) => match text_of(&chunk.content) {
            Some(delta) => vec![RunEvent::Text { run_id: rid(), delta }],
            None => vec![],
        },
        acp::SessionUpdate::AgentThoughtChunk(chunk) => match text_of(&chunk.content) {
            Some(delta) => vec![RunEvent::Thinking { run_id: rid(), delta }],
            None => vec![],
        },
        // A tool call is announced → ToolStart; its completion arrives as a
        // ToolCallUpdate with a terminal status → ToolEnd.
        acp::SessionUpdate::ToolCall(call) => vec![RunEvent::ToolStart {
            run_id: rid(),
            tool_call_id: call.tool_call_id.0.to_string(),
            title: call.title,
            tool_kind: map_kind(call.kind),
            locations: map_locations(&call.locations),
            raw_input: call.raw_input.as_ref().map(ToString::to_string),
        }],
        acp::SessionUpdate::ToolCallUpdate(update) => match update.fields.status {
            // Terminal status → ToolEnd carrying the result content + raw output
            // + the files it touched.
            Some(status @ (acp::ToolCallStatus::Completed | acp::ToolCallStatus::Failed)) => {
                vec![RunEvent::ToolEnd {
                    run_id: rid(),
                    tool_call_id: update.tool_call_id.0.to_string(),
                    ok: matches!(status, acp::ToolCallStatus::Completed),
                    content: tool_output(&update.fields),
                    raw_output: update.fields.raw_output.as_ref().map(ToString::to_string),
                    locations: update.fields.locations.as_deref().map(map_locations).unwrap_or_default(),
                }]
            }
            // pending / in_progress / no status change → no terminal event yet.
            _ => vec![],
        },
        acp::SessionUpdate::Plan(plan) => {
            let entries = plan
                .entries
                .into_iter()
                .map(|e| PlanEntry {
                    content: e.content,
                    status: map_plan_status(e.status),
                    priority: Some(map_plan_priority(e.priority)),
                })
                .collect();
            vec![RunEvent::Plan { run_id: rid(), entries }]
        }
        // user echo / available-commands / current-mode / usage / etc. have no
        // place in our stream (and `SessionUpdate` is #[non_exhaustive]).
        _ => vec![],
    }
}

/// Extract plain text from an ACP content block (only `text` blocks carry it).
fn text_of(block: &acp::ContentBlock) -> Option<String> {
    match block {
        acp::ContentBlock::Text(t) => Some(t.text.clone()),
        _ => None,
    }
}

/// Flatten an ACP tool call's result — its `content` blocks (text), else the
/// `raw_output` JSON — into `ToolEnd.output`, so the host can show what the tool
/// returned (the result/diff), not just that it finished.
fn tool_output(fields: &acp::ToolCallUpdateFields) -> Option<String> {
    if let Some(blocks) = &fields.content {
        let text = blocks.iter().filter_map(tool_content_text).collect::<Vec<_>>().join("\n");
        if !text.trim().is_empty() {
            return Some(text);
        }
    }
    fields.raw_output.as_ref().map(ToString::to_string)
}

/// Text from one tool-call content block (text content verbatim; a diff/other is
/// noted by kind).
fn tool_content_text(content: &acp::ToolCallContent) -> Option<String> {
    match content {
        acp::ToolCallContent::Content(c) => text_of(&c.content),
        acp::ToolCallContent::Diff(_) => Some("[diff]".to_owned()),
        _ => None,
    }
}

/// ACP `ToolCallLocation`s → our neutral [`ToolLocation`]s (the files the call
/// touches), so the host can show the subject + offer follow-along.
fn map_locations(locs: &[acp::ToolCallLocation]) -> Vec<ToolLocation> {
    locs.iter()
        .map(|l| ToolLocation { path: l.path.to_string_lossy().into_owned(), line: l.line })
        .collect()
}

/// ACP tool `kind` → our neutral [`ToolKind`] (we extended `ToolKind` to mirror
/// ACP's set for exactly this; `think`/`switch_mode`/unknown → `Other`).
fn map_kind(kind: acp::ToolKind) -> ToolKind {
    match kind {
        acp::ToolKind::Read => ToolKind::Read,
        acp::ToolKind::Edit => ToolKind::Edit,
        acp::ToolKind::Delete => ToolKind::Delete,
        acp::ToolKind::Move => ToolKind::Move,
        acp::ToolKind::Search => ToolKind::Search,
        acp::ToolKind::Execute => ToolKind::Execute,
        acp::ToolKind::Fetch => ToolKind::Fetch,
        _ => ToolKind::Other,
    }
}

fn map_plan_status(status: acp::PlanEntryStatus) -> PlanEntryStatus {
    match status {
        acp::PlanEntryStatus::Pending => PlanEntryStatus::Pending,
        acp::PlanEntryStatus::InProgress => PlanEntryStatus::InProgress,
        acp::PlanEntryStatus::Completed => PlanEntryStatus::Completed,
        _ => PlanEntryStatus::Pending,
    }
}

fn map_plan_priority(priority: acp::PlanEntryPriority) -> PlanEntryPriority {
    match priority {
        acp::PlanEntryPriority::High => PlanEntryPriority::High,
        acp::PlanEntryPriority::Medium => PlanEntryPriority::Medium,
        acp::PlanEntryPriority::Low => PlanEntryPriority::Low,
        _ => PlanEntryPriority::Medium,
    }
}

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

    fn chunk(text: &str) -> acp::ContentChunk {
        acp::ContentChunk::new(acp::ContentBlock::from(text))
    }

    #[test]
    fn message_vs_thought_chunks_split_correctly() {
        let msg = session_update_to_events("r1", acp::SessionUpdate::AgentMessageChunk(chunk("hello")));
        assert!(matches!(msg.as_slice(), [RunEvent::Text { delta, .. }] if delta == "hello"));

        let thought = session_update_to_events("r1", acp::SessionUpdate::AgentThoughtChunk(chunk("hmm")));
        assert!(matches!(thought.as_slice(), [RunEvent::Thinking { delta, .. }] if delta == "hmm"));

        // The user-message echo has no place in our stream.
        let user = session_update_to_events("r1", acp::SessionUpdate::UserMessageChunk(chunk("u")));
        assert!(user.is_empty());
    }
}