#!/usr/bin/env bash
# archeflow-event.sh — Append a structured event to an ArcheFlow run's JSONL log.
#
# Usage: ./lib/archeflow-event.sh <run_id> <type> <phase> <agent> '<json_data>' [parent_seqs]
#
# Examples:
#   ./lib/archeflow-event.sh 2026-04-03-der-huster run.start plan "" '{"task":"Write Der Huster"}'
#   ./lib/archeflow-event.sh 2026-04-03-der-huster agent.complete plan creator '{"duration_ms":167522}' 2
#   ./lib/archeflow-event.sh 2026-04-03-der-huster phase.transition do "" '{"from":"plan","to":"do"}' 3,4
#   ./lib/archeflow-event.sh 2026-04-03-der-huster fix.applied act "" '{"source":"guardian"}' 8
#
# Parent seqs: comma-separated seq numbers of causal parent events (DAG).
#   "2"   → single parent [2]
#   "3,4" → multiple parents [3,4] (fan-in)
#   ""    → root event []
#
# Events are appended to .archeflow/events/<run_id>.jsonl
# If the events directory doesn't exist, it is created automatically.

set -euo pipefail

if [[ $# -lt 4 ]]; then
  echo "Usage: $0 <run_id> <type> <phase> <agent> [json_data] [parent_seqs]" >&2
  exit 1
fi

RUN_ID="$1"
TYPE="$2"
PHASE="$3"
AGENT="$4"
DATA="${5:-"{}"}"
PARENT_RAW="${6:-}"

EVENTS_DIR=".archeflow/events"
EVENT_FILE="${EVENTS_DIR}/${RUN_ID}.jsonl"

mkdir -p "$EVENTS_DIR"

# Determine sequence number (count existing lines + 1)
if [[ -f "$EVENT_FILE" ]]; then
  SEQ=$(( $(wc -l < "$EVENT_FILE") + 1 ))
else
  SEQ=1
fi

TS=$(date -u +%Y-%m-%dT%H:%M:%SZ)

# Validate JSON data
if ! echo "$DATA" | jq empty 2>/dev/null; then
  echo "Error: invalid JSON in data argument: $DATA" >&2
  exit 1
fi

# Build parent array from comma-separated seq numbers
if [[ -z "$PARENT_RAW" ]]; then
  PARENT_JSON="[]"
elif [[ "$PARENT_RAW" =~ ^[0-9]+(,[0-9]+)*$ ]]; then
  PARENT_JSON="[${PARENT_RAW}]"
else
  echo "Error: invalid parent format (expected comma-separated integers): $PARENT_RAW" >&2
  exit 1
fi

# Construct the event using jq for reliable JSON assembly
# Agent is passed as --arg (string), then converted to null if empty via jq expression
EVENT=$(jq -cn \
  --arg ts "$TS" \
  --arg run_id "$RUN_ID" \
  --argjson seq "$SEQ" \
  --argjson parent "$PARENT_JSON" \
  --arg type "$TYPE" \
  --arg phase "$PHASE" \
  --arg agent_raw "$AGENT" \
  --argjson data "$DATA" \
  '{ts:$ts, run_id:$run_id, seq:$seq, parent:$parent, type:$type, phase:$phase, agent:(if $agent_raw == "" then null else $agent_raw end), data:$data}'
)

echo "$EVENT" >> "$EVENT_FILE"

# Print confirmation to stderr (non-intrusive)
echo "[archeflow-event] #${SEQ} ${TYPE} (${PHASE}/${AGENT:-_})" >&2