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

readonly SCRIPT_DIR="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd -P)"
if (( $# > 1 )); then
  printf '::error::gate-matrix-lint: expected zero arguments or one repository root\n' >&2
  exit 2
fi

if (( $# == 1 )); then
  if [[ ! -d "$1" ]]; then
    printf '::error::gate-matrix-lint: repository root is not a directory: %s\n' "$1" >&2
    exit 2
  fi
  REPO_ROOT="$(cd -- "$1" && pwd -P)"
else
  REPO_ROOT="$(git -C "${SCRIPT_DIR}" rev-parse --show-toplevel)"
  EXPECTED_SCRIPT_DIR="$(cd -- "${REPO_ROOT}/.github/scripts" && pwd -P)"
  if [[ "${SCRIPT_DIR}" != "${EXPECTED_SCRIPT_DIR}" ]]; then
    printf '::error::gate-matrix-lint: script location must be repository .github/scripts directory\n' >&2
    exit 1
  fi
fi

readonly REPO_ROOT
readonly MATRIX="${REPO_ROOT}/.github/ci-gate-matrix.yml"
# Deliberately a literal: a gate silently appearing or disappearing is the drift this lint exists to
# catch, so growing the matrix is an explicit edit here. 37 after removing the sample-only Poster
# migration gate; the HTTP Client platform hardening
# which registered httpclient-spring62-runtime as a delegated-pending control — the 6.2 *runtime*
# claim, distinct from the API-surface scan that was standing in for it.
readonly EXPECTED_GATE_COUNT=37

if [[ ! -f "${MATRIX}" ]]; then
  printf '::error::gate-matrix-lint: missing %s\n' "${MATRIX}" >&2
  exit 1
fi

records="$(
  awk '
    function flush() {
      if (id != "") {
        printf "%s\t%s\t%s\t%s\t%s\t%s\t%s\n", id, blocking, mechanism, ref, workflow, job, execution
      }
    }
    /^[[:space:]]*-[[:space:]]+id:[[:space:]]*/ {
      flush()
      id=$0
      sub(/^[[:space:]]*-[[:space:]]+id:[[:space:]]*/, "", id)
      blocking=mechanism=ref=workflow=job=execution=""
      next
    }
    /^[[:space:]]+release_blocking:[[:space:]]*/ {
      blocking=$0
      sub(/^[[:space:]]+release_blocking:[[:space:]]*/, "", blocking)
      next
    }
    /^[[:space:]]+mechanism:[[:space:]]*/ {
      mechanism=$0
      sub(/^[[:space:]]+mechanism:[[:space:]]*/, "", mechanism)
      next
    }
    /^[[:space:]]+ref:[[:space:]]*/ {
      ref=$0
      sub(/^[[:space:]]+ref:[[:space:]]*/, "", ref)
      next
    }
    /^[[:space:]]+workflow:[[:space:]]*/ {
      workflow=$0
      sub(/^[[:space:]]+workflow:[[:space:]]*/, "", workflow)
      next
    }
    /^[[:space:]]+job:[[:space:]]*/ {
      job=$0
      sub(/^[[:space:]]+job:[[:space:]]*/, "", job)
      next
    }
    /^[[:space:]]+execution:[[:space:]]*/ {
      execution=$0
      sub(/^[[:space:]]+execution:[[:space:]]*/, "", execution)
      next
    }
    END { flush() }
  ' "${MATRIX}"
)"

declare -A seen_ids=()
declare -a failures=()
total=0
verified=0
delegated=0

job_body() {
  local workflow_file="$1"
  local job_id="$2"
  awk -v target="${job_id}" '
    $0 ~ "^  " target ":[[:space:]]*$" { inside=1; print; next }
    inside && $0 ~ "^  [A-Za-z0-9_-]+:[[:space:]]*$" { exit }
    inside { print }
  ' "${workflow_file}"
}

gradle_command_has_safe_literal_grammar() {
  local command="$1"
  [[ "${command}" =~ ^\./gradlew([[:space:]]+[A-Za-z0-9_.:/@=,+-]+)+[[:space:]]*$ ]]
}

gradle_token_suppresses_execution() {
  local token="$1"
  case "${token}" in
    '--dry-run'|'--dry-run='*|'-m'|'-x'|'-x'*|'--exclude-task'|'--exclude-task='*) return 0 ;;
    *) return 1 ;;
  esac
}

gradle_token_is_allowed_gate_argument() {
  local token="$1"
  case "${token}" in
    '--no-daemon'|'--stacktrace'|'--warning-mode=fail') return 0 ;;
  esac
  [[ "${token}" =~ ^:?[A-Za-z0-9_][A-Za-z0-9_.-]*(:[A-Za-z0-9_][A-Za-z0-9_.-]*)*$ ]]
}

gradle_plugin_is_applied() {
  local plugin_id="$1"
  grep -RqsF --include='build.gradle' -- "id '${plugin_id}'" "${REPO_ROOT}/src" \
    || grep -RqsF --include='build.gradle' -- "id \"${plugin_id}\"" "${REPO_ROOT}/src" \
    || grep -RqsF --include='build.gradle' -- "apply plugin: '${plugin_id}'" "${REPO_ROOT}/src" \
    || grep -RqsF --include='build.gradle' -- "apply plugin: \"${plugin_id}\"" "${REPO_ROOT}/src"
}

gradle_custom_task_is_registered_in_build_file() {
  local task_name="$1"
  local build_file="$2"
  if grep -qsE -- "tasks\\.register\\(['\"]${task_name}['\"]" "${build_file}"; then
    return 0
  fi

  awk -v required_task="${task_name}" '
    index($0, "registerStrictQualificationTest(") > 0 { inside_registration=1 }
    inside_registration && /^[[:space:]]*name:[[:space:]]*/ {
      candidate=$0
      sub(/^[[:space:]]*name:[[:space:]]*/, "", candidate)
      quote=substr(candidate, 1, 1)
      if (quote != "\"" && quote != sprintf("%c", 39)) {
        next
      }
      candidate=substr(candidate, 2)
      closing_quote=index(candidate, quote)
      if (closing_quote == 0) {
        next
      }
      candidate=substr(candidate, 1, closing_quote - 1)
      if (candidate == required_task) {
        found=1
      }
    }
    inside_registration && /\)[[:space:]]*$/ { inside_registration=0 }
    END { exit found ? 0 : 1 }
  ' "${build_file}"
}

gradle_custom_task_is_registered() {
  local task_name="$1"
  local build_file
  while IFS= read -r -d '' build_file; do
    if gradle_custom_task_is_registered_in_build_file "${task_name}" "${build_file}"; then
      return 0
    fi
  done < <(find "${REPO_ROOT}/src" -type f -name '*.gradle' -print0)
  return 1
}

gradle_token_matches_registered_task() {
  local token="$1"
  local required_task="$2"
  local project_path build_file
  if [[ "${token}" == "${required_task}" || "${token}" == ":${required_task}" ]]; then
    return 0
  fi
  if [[ "${token}" != :* || "${token}" != *:"${required_task}" ]]; then
    return 1
  fi
  project_path="${token%:"${required_task}"}"
  project_path="${project_path#:}"
  project_path="${project_path%:}"
  build_file="${REPO_ROOT}/src/${project_path//:/\/}/build.gradle"
  [[ -f "${build_file}" ]] \
    && gradle_custom_task_is_registered_in_build_file "${required_task}" "${build_file}"
}

job_runs_gradle_task() {
  local workflow_file="$1"
  local job_id="$2"
  local required_task="$3"
  local command token
  local found_task suppressed
  local -a tokens=()

  while IFS= read -r command; do
    if ! gradle_command_has_safe_literal_grammar "${command}"; then
      continue
    fi
    read -r -a tokens <<< "${command}"
    if (( ${#tokens[@]} < 2 )) || [[ "${tokens[0]}" != './gradlew' ]]; then
      continue
    fi
    found_task=0
    suppressed=0
    for token in "${tokens[@]:1}"; do
      case "${token}" in
        '&&'|'||'|';'|'|'|'#'*) break ;;
      esac
      if gradle_token_suppresses_execution "${token}"; then
        suppressed=1
        break
      fi
      if ! gradle_token_is_allowed_gate_argument "${token}"; then
        suppressed=1
        break
      fi
      if gradle_token_matches_registered_task "${token}" "${required_task}"; then
        found_task=1
      fi
    done
    if (( found_task == 1 && suppressed == 0 )); then
      return 0
    fi
  done < <(
    job_body "${workflow_file}" "${job_id}" | awk '
      /^[[:space:]]+(-[[:space:]]+)?run:[[:space:]]+/ {
        command=$0
        sub(/^[[:space:]]+(-[[:space:]]+)?run:[[:space:]]+/, "", command)
        if (command !~ /^(\||>)/) {
          print command
        }
      }
    '
  )
  return 1
}

while IFS=$'\t' read -r id blocking mechanism ref workflow job execution; do
  [[ -z "${id}" ]] && continue
  total=$((total + 1))

  if [[ -n "${seen_ids[${id}]:-}" ]]; then
    failures+=("duplicate gate id '${id}'")
  fi
  seen_ids["${id}"]=1

  if [[ -z "${blocking}" || -z "${mechanism}" || -z "${ref}" || -z "${workflow}" \
        || -z "${job}" || -z "${execution}" ]]; then
    failures+=("gate '${id}' has an empty required field")
    continue
  fi
  if [[ ! "${blocking}" =~ ^(true|false|conditional)$ ]]; then
    failures+=("gate '${id}' has invalid release_blocking '${blocking}'")
  fi
  if [[ ! "${workflow}" =~ ^[A-Za-z0-9._-]+\.ya?ml$ || ! "${job}" =~ ^[A-Za-z0-9_-]+$ ]]; then
    failures+=("gate '${id}' has an unsafe workflow or job identifier")
    continue
  fi

  workflow_file="${REPO_ROOT}/.github/workflows/${workflow}"
  if [[ ! -f "${workflow_file}" ]]; then
    failures+=("gate '${id}' references missing workflow '.github/workflows/${workflow}'")
    continue
  fi
  if ! grep -Eqs -- "^[[:space:]]{2}${job}:[[:space:]]*$" "${workflow_file}"; then
    failures+=("gate '${id}' references missing job '${job}' in '${workflow}'")
    continue
  fi

  case "${mechanism}" in
    gradle-custom-task)
      if [[ ! "${ref}" =~ ^[A-Za-z_][A-Za-z0-9_-]*$ ]]; then
        failures+=("gate '${id}' has unsafe Gradle custom task ref '${ref}'")
        continue
      fi
      if ! gradle_custom_task_is_registered "${ref}"; then
        failures+=("gate '${id}' references unregistered Gradle task '${ref}'")
        continue
      fi
      ;;
    gradle-plugin-task)
      plugin="${ref%@*}"
      task="${ref#*@}"
      if [[ "${plugin}" == "${ref}" \
            || ! "${plugin}" =~ ^[A-Za-z][A-Za-z0-9.-]*$ \
            || ! "${task}" =~ ^[A-Za-z_][A-Za-z0-9_-]*$ ]]; then
        failures+=("gate '${id}' has unsafe Gradle plugin task ref '${ref}'")
        continue
      fi
      if ! gradle_plugin_is_applied "${plugin}"; then
        failures+=("gate '${id}' references unapplied Gradle plugin '${plugin}'")
        continue
      fi
      ;;
    contract-test)
      if [[ "${ref}" == /* || "${ref}" == *".."* || ! -f "${REPO_ROOT}/src/${ref}" ]]; then
        failures+=("gate '${id}' references missing or unsafe contract test 'src/${ref}'")
        continue
      fi
      ;;
    workflow-job)
      if [[ "${ref}" != "${job}" ]]; then
        failures+=("gate '${id}' workflow-job ref '${ref}' must equal job '${job}'")
        continue
      fi
      ;;
    delegated-pending)
      delegated=$((delegated + 1))
      printf "gate '%s': explicitly delegated-pending\n" "${id}"
      continue
      ;;
    *)
      failures+=("gate '${id}' has unknown mechanism '${mechanism}'")
      continue
      ;;
  esac

  case "${execution}" in
    check)
      if ! job_runs_gradle_task "${workflow_file}" "${job}" 'check'; then
        failures+=("gate '${id}' expects Gradle check in job '${job}'")
        continue
      fi
      if [[ "${mechanism}" == "gradle-custom-task" ]] \
          && ! grep -RqsE -- "dependsOn.*named\\(['\"]${ref}['\"]\\)" "${REPO_ROOT}/src" \
            --include='build.gradle'; then
        failures+=("gate '${id}' task '${ref}' exists but is not wired into Gradle check")
        continue
      fi
      ;;
    explicit)
      if ! job_runs_gradle_task "${workflow_file}" "${job}" "${ref}"; then
        failures+=("gate '${id}' task '${ref}' is not explicit in job '${job}'")
        continue
      fi
      ;;
    job)
      ;;
    *)
      failures+=("gate '${id}' has unknown execution '${execution}'")
      continue
      ;;
  esac

  verified=$((verified + 1))
done <<< "${records}"

if (( total != EXPECTED_GATE_COUNT )); then
  failures+=("matrix has ${total} gates; expected ${EXPECTED_GATE_COUNT}")
fi

printf 'gate-matrix-lint: %d gates, %d verified, %d delegated-pending\n' \
  "${total}" "${verified}" "${delegated}"
if (( ${#failures[@]} > 0 )); then
  printf '::error::gate-matrix-lint: %d drift(s) found\n' "${#failures[@]}" >&2
  for failure in "${failures[@]}"; do
    printf '  - %s\n' "${failure}" >&2
  done
  exit 1
fi
printf 'gate-matrix-lint: OK\n'