#!/usr/bin/env bash

set -Eeuo pipefail
# Do not expose headers, cookies, or future sensitive values through caller xtrace.
set +x
umask 077

readonly EXPECTED_CANDIDATE_SHA256="de7ebd4f69cd7d2204ee633e074bf6a4370a6f5e3f3fac9067b099d5d75269b5"
readonly EXPECTED_PRE_CUTOVER_SHA256="5b5941519ab677f751568827aa4f315193dfbd9eeac5e8a4ad85d724aaefe16f"
readonly EXPECTED_PRE_CUTOVER_HEALTH_SHA256="6b683cb16987ff1f5ded22e9847ac0a45995947927c459b21f427523a41c7484"
readonly REPOSITORY_ROOT="/home/donghyeon/workspace/platform"
readonly CANDIDATE="${REPOSITORY_ROOT}/infrastructure/networking/host-nginx/learn-services.conf"
readonly ACTIVE="/etc/nginx/sites-available/learn-services"
readonly ENABLED="/etc/nginx/sites-enabled/learn-services"
readonly CURL_BIN="/usr/bin/curl"
readonly JQ_BIN="/usr/bin/jq"
readonly NGINX_BIN="/usr/sbin/nginx"
readonly SYSTEMCTL_BIN="/usr/bin/systemctl"
readonly INSTALL_BIN="/usr/bin/install"
readonly SHA256SUM_BIN="/usr/bin/sha256sum"
readonly STAT_BIN="/usr/bin/stat"
readonly READLINK_BIN="/usr/bin/readlink"
readonly MKTEMP_BIN="/usr/bin/mktemp"
readonly RM_BIN="/usr/bin/rm"
readonly DATE_BIN="/usr/bin/date"
readonly AWK_BIN="/usr/bin/awk"
readonly SLEEP_BIN="/usr/bin/sleep"

fail() {
  printf 'ERROR: %s\n' "$*" >&2
  return 1
}

usage() {
  printf '%s\n' \
    'Usage: sudo bash scripts/bootstrap/apply-host-nginx-gitea.sh --execute' \
    '' \
    'Backs up the active learn-services site, installs the reviewed Gitea proxy,' \
    'tests and reloads Nginx, then runs local acceptance checks. Any failure after' \
    'the active file changes triggers an automatic restore and reload.'
}

[[ "${1:-}" == "--execute" && "$#" -eq 1 ]] || {
  usage
  exit 2
}
[[ "$EUID" -eq 0 ]] || fail "run this script through sudo"
[[ -t 0 ]] || fail "an interactive terminal is required"

for required_binary in \
  "$CURL_BIN" "$JQ_BIN" "$NGINX_BIN" "$SYSTEMCTL_BIN" "$INSTALL_BIN" \
  "$SHA256SUM_BIN" "$STAT_BIN" "$READLINK_BIN" "$MKTEMP_BIN" \
  "$RM_BIN" "$DATE_BIN" "$AWK_BIN" "$SLEEP_BIN"; do
  [[ -x "$required_binary" ]] || fail "required executable is missing: ${required_binary}"
done

[[ -f "$CANDIDATE" && ! -L "$CANDIDATE" ]] || fail "unsafe candidate: ${CANDIDATE}"
[[ -f "$ACTIVE" && ! -L "$ACTIVE" ]] || fail "unsafe active file: ${ACTIVE}"
[[ -L "$ENABLED" ]] || fail "enabled path is not a symlink: ${ENABLED}"
[[ "$("$READLINK_BIN" -f "$ENABLED")" == "$ACTIVE" ]] || fail "enabled symlink target changed"
[[ "$("$STAT_BIN" --format='%U:%G %a' "$ACTIVE")" == "root:root 644" ]] || \
  fail "active file owner or mode changed"
"$SYSTEMCTL_BIN" is-active --quiet nginx || fail "nginx is not active"

readonly TEMP_DIR="$("$MKTEMP_BIN" -d /tmp/nginx-gitea-cutover.XXXXXX)"
readonly CANDIDATE_SNAPSHOT="${TEMP_DIR}/learn-services.candidate"
readonly DIRECT_HEALTH="${TEMP_DIR}/direct-health.json"
readonly NGINX_HEALTH="${TEMP_DIR}/nginx-health.json"
readonly LOGIN_HEADERS="${TEMP_DIR}/login-headers"
rollback_armed=0
backup=""

cleanup() {
  case "$TEMP_DIR" in
    /tmp/nginx-gitea-cutover.*)
      "$RM_BIN" -rf -- "$TEMP_DIR"
      ;;
    *)
      printf 'WARNING: refusing to remove unexpected temp path: %s\n' "$TEMP_DIR" >&2
      ;;
  esac
}

rollback() {
  local restore_install_rc
  local restore_test_rc
  local restore_reload_rc

  set +e
  printf '\nROLLBACK: restoring %s\n' "$backup" >&2
  if "$INSTALL_BIN" -o root -g root -m 0644 "$backup" "$ACTIVE" &&
    [[ "$("$SHA256SUM_BIN" "$ACTIVE" | "$AWK_BIN" '{print $1}')" == "$("$SHA256SUM_BIN" "$backup" | "$AWK_BIN" '{print $1}')" ]]; then
    restore_install_rc=0
  else
    restore_install_rc=1
  fi
  "$NGINX_BIN" -t
  restore_test_rc=$?
  if (( restore_install_rc == 0 && restore_test_rc == 0 )); then
    if "$SYSTEMCTL_BIN" reload nginx &&
      "$SYSTEMCTL_BIN" is-active --quiet nginx &&
      wait_for_rollback_state; then
      restore_reload_rc=0
    else
      restore_reload_rc=1
    fi
  else
    restore_reload_rc=1
  fi

  if (( restore_install_rc == 0 && restore_test_rc == 0 && restore_reload_rc == 0 )); then
    rollback_armed=0
    printf 'ROLLBACK complete. Active config and response were restored.\n' >&2
  else
    printf 'CRITICAL: automatic rollback failed; backup remains at %s\n' "$backup" >&2
  fi
}

on_exit() {
  local rc=$?

  trap - EXIT INT TERM
  if (( rc != 0 && rollback_armed == 1 )); then
    rollback
  fi
  cleanup
  exit "$rc"
}

trap on_exit EXIT
trap 'exit 130' INT
trap 'exit 143' TERM

"$INSTALL_BIN" -o root -g root -m 0600 "$CANDIDATE" "$CANDIDATE_SNAPSHOT"
readonly CANDIDATE_SHA256="$("$SHA256SUM_BIN" "$CANDIDATE_SNAPSHOT" | "$AWK_BIN" '{print $1}')"
readonly ACTIVE_SHA256="$("$SHA256SUM_BIN" "$ACTIVE" | "$AWK_BIN" '{print $1}')"
[[ "$CANDIDATE_SHA256" == "$EXPECTED_CANDIDATE_SHA256" ]] || \
  fail "candidate digest changed: ${CANDIDATE_SHA256}"
if [[ "$ACTIVE_SHA256" != "$EXPECTED_PRE_CUTOVER_SHA256" && "$ACTIVE_SHA256" != "$CANDIDATE_SHA256" ]]; then
  fail "active config has an unexpected digest: ${ACTIVE_SHA256}"
fi

check_health_json() {
  local path="$1"

  "$JQ_BIN" -e '
    .status == "pass" and
    ([.checks["database:ping"][], .checks["cache:ping"][]] |
      all(.status == "pass"))
  ' "$path" >/dev/null
}

pre_cutover_check() {
  "$CURL_BIN" --noproxy '*' --fail-with-body --silent --show-error --max-time 10 \
    --header 'Host: git.learn.hyeonworks.com' \
    http://127.0.0.1:30080/api/healthz >"$DIRECT_HEALTH"
  check_health_json "$DIRECT_HEALTH"
}

wait_for_nginx_health() {
  local attempt
  local probe_metadata=""
  local http_code="curl-error"
  local content_type="unavailable"
  local size_download="0"
  local body_sha256=""
  local classification="transport-error"
  local consecutive_passes=0

  for ((attempt = 1; attempt <= 10; attempt++)); do
    if probe_metadata="$(
      "$CURL_BIN" --noproxy '*' --silent --connect-timeout 1 --max-time 2 \
        --resolve git.learn.hyeonworks.com:443:127.0.0.1 \
        --output "$NGINX_HEALTH" \
        --write-out $'%{http_code}\t%{content_type}\t%{size_download}' \
        https://git.learn.hyeonworks.com/api/healthz
    )"; then
      IFS=$'\t' read -r http_code content_type size_download <<<"$probe_metadata"
      body_sha256="$(
        "$SHA256SUM_BIN" "$NGINX_HEALTH" | "$AWK_BIN" '{print $1}'
      )"

      if [[ "$http_code" == "200" ]] &&
        check_health_json "$NGINX_HEALTH" 2>/dev/null; then
        classification="healthy-json"
        consecutive_passes=$((consecutive_passes + 1))
        if (( consecutive_passes >= 2 )); then
          printf 'Nginx proxy health stabilized after %d probes.\n' "$attempt"
          return 0
        fi
      else
        consecutive_passes=0
        if [[ "$body_sha256" == "$EXPECTED_PRE_CUTOVER_HEALTH_SHA256" ]]; then
          classification="stale-old-generation"
        elif [[ "$http_code" =~ ^(502|503|504)$ ]]; then
          classification="transient-upstream"
        elif "$JQ_BIN" -e '
          type == "object" and
          has("status") and
          (.checks | type == "object")
        ' "$NGINX_HEALTH" >/dev/null 2>&1; then
          classification="unhealthy-health-json"
        else
          printf 'ERROR: unexpected Nginx health response (status=%s, content-type=%s, bytes=%s, sha256=%s)\n' \
            "$http_code" "${content_type:-none}" "$size_download" "$body_sha256" >&2
          return 1
        fi
      fi
    else
      http_code="curl-error"
      content_type="unavailable"
      size_download="0"
      body_sha256=""
      classification="transport-error"
      consecutive_passes=0
    fi

    if (( attempt < 10 )); then
      "$SLEEP_BIN" 1
    fi
  done

  fail "Nginx health did not converge during the bounded retry window (classification=${classification}, status=${http_code}, content-type=${content_type:-none}, bytes=${size_download})"
}

wait_for_rollback_state() {
  local attempt
  local probe_metadata=""
  local http_code="curl-error"
  local content_type="unavailable"
  local size_download="0"
  local body_sha256=""

  for ((attempt = 1; attempt <= 10; attempt++)); do
    if probe_metadata="$(
      "$CURL_BIN" --noproxy '*' --silent --connect-timeout 1 --max-time 2 \
        --resolve git.learn.hyeonworks.com:443:127.0.0.1 \
        --output "$NGINX_HEALTH" \
        --write-out $'%{http_code}\t%{content_type}\t%{size_download}' \
        https://git.learn.hyeonworks.com/api/healthz
    )"; then
      IFS=$'\t' read -r http_code content_type size_download <<<"$probe_metadata"
      body_sha256="$(
        "$SHA256SUM_BIN" "$NGINX_HEALTH" | "$AWK_BIN" '{print $1}'
      )"
      if [[ "$http_code" == "200" &&
        "$body_sha256" == "$EXPECTED_PRE_CUTOVER_HEALTH_SHA256" ]]; then
        if (( attempt > 1 )); then
          printf 'Rollback proxy state stabilized after %d probes.\n' "$attempt" >&2
        fi
        return 0
      fi
    else
      http_code="curl-error"
      content_type="unavailable"
      size_download="0"
      body_sha256=""
    fi

    if (( attempt < 10 )); then
      "$SLEEP_BIN" 1
    fi
  done

  printf 'CRITICAL: rollback response did not converge (status=%s, content-type=%s, bytes=%s, sha256=%s)\n' \
    "$http_code" "${content_type:-none}" "$size_download" "${body_sha256:-none}" >&2
  return 1
}

post_cutover_checks() {
  local id_body
  local redirect_result

  wait_for_nginx_health

  id_body="$(
    "$CURL_BIN" --noproxy '*' --fail-with-body --silent --show-error --max-time 10 \
      --resolve id.learn.hyeonworks.com:443:127.0.0.1 \
      https://id.learn.hyeonworks.com/
  )"
  [[ "$id_body" == "Keycloak domain reached Nginx successfully" ]] || \
    fail "Keycloak hold response changed"

  redirect_result="$(
    "$CURL_BIN" --noproxy '*' --silent --show-error --max-time 10 \
      --resolve git.learn.hyeonworks.com:80:127.0.0.1 \
      --output /dev/null --write-out $'%{http_code}\n%{redirect_url}' \
      http://git.learn.hyeonworks.com/api/healthz
  )"
  [[ "$redirect_result" == $'301\nhttps://git.learn.hyeonworks.com/api/healthz' ]] || \
    fail "HTTP redirect check failed: ${redirect_result}"

  if "$CURL_BIN" --noproxy '*' --insecure --silent --output /dev/null --max-time 5 \
    --resolve unconfigured.invalid:443:127.0.0.1 \
    https://unconfigured.invalid/ 2>/dev/null; then
    fail "unknown TLS hostname was not rejected"
  fi

  "$CURL_BIN" --noproxy '*' --fail-with-body --silent --show-error --max-time 10 \
    --resolve git.learn.hyeonworks.com:443:127.0.0.1 \
    --dump-header "$LOGIN_HEADERS" --output /dev/null \
    https://git.learn.hyeonworks.com/user/login
  "$AWK_BIN" '
    BEGIN { found = 0; insecure = 0 }
    tolower($0) ~ /^set-cookie:/ {
      found++
      if (tolower($0) !~ /; secure([;[:space:]]|$)/) insecure = 1
    }
    END { exit(found == 0 || insecure) }
  ' "$LOGIN_HEADERS" || fail "login cookie Secure check failed"
}

pre_cutover_check
"$NGINX_BIN" -t

if [[ "$ACTIVE_SHA256" == "$CANDIDATE_SHA256" ]]; then
  post_cutover_checks
  printf 'The reviewed Host Nginx configuration is already active and healthy.\n'
  exit 0
fi

backup="${ACTIVE}.before-gitea-$("$DATE_BIN" +%Y%m%d%H%M%S)"
[[ ! -e "$backup" && ! -L "$backup" ]] || fail "backup path already exists: ${backup}"

printf '\nActive SHA-256:    %s\n' "$ACTIVE_SHA256"
printf 'Candidate SHA-256: %s\n' "$CANDIDATE_SHA256"
printf 'Planned backup:      %s\n' "$backup"
printf 'Type APPLY to replace the Host Nginx site: '
read -r confirmation
[[ "$confirmation" == "APPLY" ]] || fail "cancelled"

"$INSTALL_BIN" -o root -g root -m 0644 "$ACTIVE" "$backup"
[[ "$("$SHA256SUM_BIN" "$backup" | "$AWK_BIN" '{print $1}')" == "$ACTIVE_SHA256" ]] || \
  fail "backup digest mismatch"

rollback_armed=1
"$INSTALL_BIN" -o root -g root -m 0644 "$CANDIDATE_SNAPSHOT" "$ACTIVE"
[[ "$("$SHA256SUM_BIN" "$ACTIVE" | "$AWK_BIN" '{print $1}')" == "$CANDIDATE_SHA256" ]] || \
  fail "installed digest mismatch"
"$NGINX_BIN" -t
"$SYSTEMCTL_BIN" reload nginx
"$SYSTEMCTL_BIN" is-active --quiet nginx
post_cutover_checks

rollback_armed=0
printf '\nCUTOVER SUCCESS\n'
printf 'Backup: %s\n' "$backup"
printf 'Candidate SHA-256: %s\n' "$CANDIDATE_SHA256"
printf 'Local HTTPS health, redirect, Secure cookie, Keycloak hold, and unknown-host rejection: PASS\n'
printf 'Run the public HTTPS and Git clone/push checks from a separate client next.\n'