#!/usr/bin/env bash
# verify-attestation.sh — verify a PropRaven Data Quality Attestation
# offline using only curl, jq, openssl, and shasum (all macOS/Linux defaults).
#
# Usage:
#   curl -sL https://propraven.com/audit/verify-attestation.sh | bash
#
# Or download and inspect first:
#   curl -O https://propraven.com/audit/verify-attestation.sh
#   bash verify-attestation.sh
#
# Exits 0 on PASS, 1 on any FAIL.

set -euo pipefail

BASE="${PROPRAVEN_BASE:-https://propraven.com}"
TMP=$(mktemp -d)
trap 'rm -rf "$TMP"' EXIT

echo "PropRaven Attestation Verifier"
echo "Base: $BASE"
echo "Tmp:  $TMP"
echo ""

echo "1/4  Fetching artifacts..."
curl -sLo "$TMP/sample.pdf"  "$BASE/audit/sample.pdf"
curl -sLo "$TMP/sample.json" "$BASE/audit/sample.json"
curl -sLo "$TMP/pubkey.b64"  "$BASE/audit/attestation-public-key.b64"

PDF_BYTES=$(wc -c < "$TMP/sample.pdf" | tr -d ' ')
echo "      sample.pdf:  $PDF_BYTES bytes"
echo "      sample.json: $(wc -c < "$TMP/sample.json" | tr -d ' ') bytes"
echo "      pubkey.b64:  $(wc -c < "$TMP/pubkey.b64"  | tr -d ' ') bytes"
echo ""

echo "2/4  Computing SHA-256 of PDF..."
ACTUAL=$(shasum -a 256 "$TMP/sample.pdf" | awk '{print $1}')
EXPECTED=$(jq -r '.content_hash_sha256' "$TMP/sample.json")
EXPECTED_BYTES=$(jq -r '.content_bytes' "$TMP/sample.json")

echo "      actual:   $ACTUAL"
echo "      expected: $EXPECTED"
if [ "$ACTUAL" != "$EXPECTED" ]; then
  echo ""
  echo "❌ FAIL — content_hash_sha256 mismatch. PDF has been altered."
  exit 1
fi
if [ "$PDF_BYTES" != "$EXPECTED_BYTES" ]; then
  echo ""
  echo "❌ FAIL — content_bytes mismatch (got $PDF_BYTES, expected $EXPECTED_BYTES)."
  exit 1
fi
echo "      ✓ hash + byte count match"
echo ""

echo "3/4  Verifying Ed25519 signature..."
# Pubkey is raw 32 bytes Ed25519, base64-encoded. openssl needs DER.
# DER prefix for Ed25519 SubjectPublicKeyInfo is 12 bytes: 30 2A 30 05 06 03 2B 65 70 03 21 00
{
  printf '\x30\x2a\x30\x05\x06\x03\x2b\x65\x70\x03\x21\x00'
  base64 -d < "$TMP/pubkey.b64"
} > "$TMP/pubkey.der"
openssl pkey -pubin -inform DER -in "$TMP/pubkey.der" -out "$TMP/pubkey.pem" 2>/dev/null

# Reconstruct the canonical message that was signed.
jq -r '.signature_message_canonical' "$TMP/sample.json" | base64 -d > "$TMP/message.bin"
jq -r '.signature_ed25519' "$TMP/sample.json" | base64 -d > "$TMP/sig.bin"

if openssl pkeyutl -verify -pubin -inkey "$TMP/pubkey.pem" \
     -rawin -in "$TMP/message.bin" -sigfile "$TMP/sig.bin" \
     >/dev/null 2>&1; then
  echo "      ✓ signature verifies against published public key"
else
  echo ""
  echo "❌ FAIL — Ed25519 signature did NOT verify."
  exit 1
fi
echo ""

echo "4/4  Summary..."
QUARTER=$(jq -r '.quarter' "$TMP/sample.json")
COUNTY=$(jq -r '.county_name' "$TMP/sample.json")
RUN_ID=$(jq -r '.audit_run_id' "$TMP/sample.json")
GENERATED=$(jq -r '.generated_at' "$TMP/sample.json")
echo "      Document:    PropRaven $COUNTY Quality Attestation, $QUARTER"
echo "      Audit run:   $RUN_ID"
echo "      Generated:   $GENERATED"
echo ""
echo "✅ PASS — this attestation is authentic and unaltered."