#!/usr/bin/env bash
set -uo pipefail

# CASAN Track C-MVP — Data-exfiltration guard (C3, V19).
#
# Content leaving the trusted boundary must not carry secrets/PII. This guard
# is the checkpoint for three egress destinations, each with its own policy:
#
#   cloud    — content about to be sent to a CLOUD model (OpenAI/Anthropic).
#              A secret => BLOCK (fail closed); PII => masked copy emitted.
#              Critical once Plan-03 wires a real cloud backend.
#   audit    — content about to be written to an audit/log record.
#              PII/secret => masked copy emitted (BLOCK if masking impossible).
#   artifact — a generated artifact about to be persisted/shared.
#              Any secret / env-token => BLOCK.
#
# It reuses security-check.sh's secret/PII detection + masking (single source of
# truth) and applies the destination policy on top. Deterministic; no model call.
#
# Usage: data-exfil-guard.sh <file> <cloud|audit|artifact> [masked-output-file]
# Exit: 0 allowed (possibly masked), 2 blocked (secret at a fail-closed boundary),
#       64 usage.

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
# shellcheck source=casan-log.sh
source "$SCRIPT_DIR/casan-log.sh"

FILE="${1:-}"
DEST="${2:-}"
MASKED_OUT="${3:-}"

if [[ -z "$FILE" || ! -f "$FILE" || -z "$DEST" ]]; then
  echo "Usage: data-exfil-guard.sh <file> <cloud|audit|artifact> [masked-output-file]" >&2
  exit 64
fi
case "$DEST" in cloud|audit|artifact) ;; *) echo "unknown destination: $DEST" >&2; exit 64 ;; esac

SCAN_OUT="$(mktemp)"
trap 'rm -f "$SCAN_OUT"' EXIT

# Deterministic detection: security-check input-mode (semantic OFF). rc==2 means
# a secret/critical pattern was found; on rc==0 SCAN_OUT holds the PII-masked copy.
CASAN_SECURITY_STRICT=0 CASAN_SEMANTIC_CLASSIFY=0 \
  bash "$SCRIPT_DIR/security-check.sh" "$FILE" "$SCAN_OUT" input >/dev/null 2>&1
SC_RC=$?

if [[ "$SC_RC" -eq 2 ]]; then
  # A secret / private key / connection string / card was detected.
  case "$DEST" in
    cloud)
      casan_log error data-exfil "DATA_EXFIL_BLOCKED destination=cloud reason=secret_would_leave_org"
      echo "DATA_EXFIL_BLOCKED destination=cloud reason=secret_in_content" >&2
      exit 2 ;;
    artifact)
      casan_log error data-exfil "DATA_EXFIL_BLOCKED destination=artifact reason=secret_or_env_token"
      echo "DATA_EXFIL_BLOCKED destination=artifact reason=secret_or_env_token" >&2
      exit 2 ;;
    audit)
      # Audit must never store a raw secret and must never lose the record; if we
      # cannot safely mask a hard secret we fail closed rather than log it raw.
      casan_log error data-exfil "DATA_EXFIL_BLOCKED destination=audit reason=unmaskable_secret"
      echo "DATA_EXFIL_BLOCKED destination=audit reason=unmaskable_secret" >&2
      exit 2 ;;
  esac
elif [[ "$SC_RC" -ne 0 ]]; then
  echo "DATA_EXFIL_SCAN_ERROR destination=$DEST rc=$SC_RC" >&2
  exit 2  # fail closed on scan error
fi

# rc==0: content is safe; SCAN_OUT is the PII-masked copy.
if [[ -n "$MASKED_OUT" ]]; then
  cp "$SCAN_OUT" "$MASKED_OUT"
fi
if ! cmp -s "$FILE" "$SCAN_OUT"; then
  casan_log info data-exfil "DATA_EXFIL_MASKED destination=$DEST (PII redacted before egress)"
  echo "DATA_EXFIL_MASKED destination=$DEST"
else
  echo "DATA_EXFIL_CLEAN destination=$DEST"
fi
exit 0