#!/usr/bin/env bash
# Praxis SessionStart hook — injects using-praxis bootstrap per host docs.
#
# Sources (official):
#   Claude Code: startup | resume | clear | compact | fork
#   Codex:       startup | resume | clear | compact
#   Copilot CLI: startup | resume | new
#   Gemini CLI:  startup | resume | clear
#
# Inject policy:
#   full  → startup, resume, clear, fork, new, unknown
#   brief → compact (avoid re-pasting full skill after compaction)
#   none  → Gemini/Antigravity when contextFileName already loads using-praxis
#           (detected: stdin has hook_event_name, no CLAUDE_PLUGIN_ROOT/PLUGIN_ROOT/COPILOT_CLI)
set -e
set -u
set -o pipefail 2>/dev/null || true

SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
PRAXIS_ROOT="$(cd "${SCRIPT_DIR}/.." && pwd)"
if [ -n "${CLAUDE_PLUGIN_ROOT:-}" ]; then
  PRAXIS_ROOT="${CLAUDE_PLUGIN_ROOT}"
elif [ -n "${PLUGIN_ROOT:-}" ]; then
  PRAXIS_ROOT="${PLUGIN_ROOT}"
fi
SKILL_PATH="${PRAXIS_ROOT}/skills/using-praxis/SKILL.md"

stdin_json=""
if [ -t 0 ]; then
  :
else
  stdin_json=$(cat 2>/dev/null || true)
fi

detect_source() {
  local raw="$1"
  if [ -z "$raw" ]; then
    printf '%s' ""
    return
  fi
  if command -v python3 >/dev/null 2>&1; then
    printf '%s' "$raw" | PYTHONIOENCODING=utf-8 python3 -c '
import json,sys
try:
    d=json.load(sys.stdin)
except Exception:
    sys.exit(0)
src=d.get("source") or d.get("Source") or ""
print(src if isinstance(src,str) else "")
' 2>/dev/null || true
    return
  fi
  printf '%s' "$raw" | tr -d '\n' | sed -n 's/.*"source"[[:space:]]*:[[:space:]]*"\([^"]*\)".*/\1/p' | head -1
}

has_hook_event_name() {
  printf '%s' "$1" | grep -q '"hook_event_name"' 2>/dev/null
}

json_escape() {
  if command -v python3 >/dev/null 2>&1; then
    PYTHONIOENCODING=utf-8 python3 -c 'import json,sys; sys.stdout.write(json.dumps(sys.stdin.read())[1:-1])'
    return
  fi
  if command -v python >/dev/null 2>&1; then
    PYTHONIOENCODING=utf-8 python -c 'import json,sys; sys.stdout.write(json.dumps(sys.stdin.read())[1:-1])'
    return
  fi
  local s
  s=$(cat)
  s="${s//\\/\\\\}"
  s="${s//\"/\\\"}"
  s="${s//$'\n'/\\n}"
  s="${s//$'\r'/\\r}"
  s="${s//$'\t'/\\t}"
  printf '%s' "$s"
}

strip_frontmatter() {
  awk '
    BEGIN { skip=0; seen=0 }
    /^---[[:space:]]*$/ {
      if (seen==0) { seen=1; skip=1; next }
      if (skip==1) { skip=0; next }
    }
    skip==0 { print }
  '
}

BRIEF_CONTENT='<EXTREMELY_IMPORTANT>
You still have Praxis after context compaction.

Continue every turn with:
`praxis: scope=<x>, loading=<skills>` (add `topology=multi-module` when required).

Load skills via the harness skill loader when available, otherwise read `skills/<name>/SKILL.md`.
Follow loaded skills and `<gate>` markers. Full triage table: skills/using-praxis/SKILL.md.
</EXTREMELY_IMPORTANT>'

build_full_content() {
  if [ ! -f "${SKILL_PATH}" ]; then
    if [[ "${SKILL_PATH}" =~ ^([a-zA-Z]):[/\\](.*) ]]; then
      local drive="${BASH_REMATCH[1]}"
      drive="$(printf '%s' "$drive" | tr '[:upper:]' '[:lower:]')"
      local rest="${BASH_REMATCH[2]//\\//}"
      SKILL_PATH="/mnt/${drive}/${rest}"
    fi
  fi
  if [ ! -f "${SKILL_PATH}" ] && [ -f "${SCRIPT_DIR}/../skills/using-praxis/SKILL.md" ]; then
    SKILL_PATH="${SCRIPT_DIR}/../skills/using-praxis/SKILL.md"
  fi
  if [ ! -f "${SKILL_PATH}" ]; then
    printf '%s' ""
    return
  fi
  local startup_skill
  startup_skill=$(strip_frontmatter < "${SKILL_PATH}")
  printf '%s' "<EXTREMELY_IMPORTANT>
You have Praxis.

Below is the full content of your 'praxis:using-praxis' skill — your introduction to using Praxis skills.
Load other Praxis skills with the harness skill loader when available, otherwise read skills/<name>/SKILL.md with the native file-read tool.

${startup_skill}
</EXTREMELY_IMPORTANT>"
}

emit() {
  local payload
  payload=$(printf '%s' "$1" | json_escape)
  local shape="$2"
  case "$shape" in
    nested)
      printf '{"hookSpecificOutput":{"hookEventName":"SessionStart","additionalContext":"%s"}}\n' "$payload"
      ;;
    flat)
      printf '{"additionalContext":"%s"}\n' "$payload"
      ;;
    *)
      printf '{"hookSpecificOutput":{"hookEventName":"SessionStart","additionalContext":"%s"}}\n' "$payload"
      ;;
  esac
}

SOURCE="$(detect_source "$stdin_json")"
SOURCE="$(printf '%s' "$SOURCE" | tr '[:upper:]' '[:lower:]')"

# Gemini/Antigravity: gemini-extension.json contextFileName already injects using-praxis.
# If the shared hooks/hooks.json also runs (same path as Claude plugins), skip duplicate body.
if has_hook_event_name "$stdin_json" \
  && [ -z "${CLAUDE_PLUGIN_ROOT:-}" ] \
  && [ -z "${PLUGIN_ROOT:-}" ] \
  && [ -z "${COPILOT_CLI:-}" ]; then
  emit "" nested
  exit 0
fi

case "${SOURCE}" in
  compact) content="${BRIEF_CONTENT}" ;;
  *) content="$(build_full_content)" ;;
esac

if [ -n "${CLAUDE_PLUGIN_ROOT:-}" ] || [ -n "${PLUGIN_ROOT:-}" ]; then
  emit "$content" nested
elif [ -n "${COPILOT_CLI:-}" ]; then
  emit "$content" flat
else
  emit "$content" nested
fi