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

ROOT=${1:-$(CDPATH='' cd -- "$(dirname -- "$0")/.." && pwd)}
registry="$ROOT/priv/repo/migration_application_compatibility.tsv"
migrations_dir="$ROOT/priv/repo/migrations"

[[ -f "$registry" ]] || {
  echo "Migration compatibility registry is missing: $registry" >&2
  exit 2
}

[[ -d "$migrations_dir" ]] || {
  echo "Migration directory is missing: $migrations_dir" >&2
  exit 2
}

mapfile -t entries < <(
  awk -F '\t' '
    $0 !~ /^#/ && NF > 0 {
      if (NF != 3 || $1 !~ /^[0-9]{14}$/ ||
          ($2 != "application_safe" && $2 != "forward_only") ||
          $3 == "" || $3 == $2) {
        print "INVALID\t" NR "\t" $0
      } else {
        print $1 "\t" $2 "\t" $3
      }
    }
  ' "$registry"
)

if [[ ${#entries[@]} -eq 0 ]]; then
  echo "Migration compatibility registry has no reviewed entries." >&2
  exit 2
fi

for entry in "${entries[@]}"; do
  if [[ "$entry" == INVALID$'\t'* ]]; then
    echo "Invalid migration registry entry: $entry" >&2
    exit 2
  fi
done

mapfile -t versions < <(printf '%s\n' "${entries[@]}" | cut -f1)
if [[ $(printf '%s\n' "${versions[@]}" | sort -u | wc -l) -ne ${#versions[@]} ]]; then
  echo "Migration compatibility registry contains a duplicate version." >&2
  exit 2
fi

first_reviewed_version=$(printf '%s\n' "${versions[@]}" | sort | head -n 1)

mapfile -t reviewed_migrations < <(
  find "$migrations_dir" -maxdepth 1 -type f -name '[0-9]*.exs' -printf '%f\n' |
    awk -F_ -v first="$first_reviewed_version" '$1 >= first {print $1}' |
    sort
)

for version in "${versions[@]}"; do
  mapfile -t files < <(
    find "$migrations_dir" -maxdepth 1 -type f -name "${version}_*.exs" -printf '%f\n'
  )
  if [[ ${#files[@]} -ne 1 ]]; then
    echo "Registry version $version must identify exactly one migration file." >&2
    exit 2
  fi
done

for version in "${reviewed_migrations[@]}"; do
  matches=$(printf '%s\n' "${versions[@]}" | grep -Fxc "$version" || true)
  if [[ "$matches" -ne 1 ]]; then
    echo "Migration $version must have exactly one reviewed registry entry." >&2
    exit 2
  fi
done

echo "Migration compatibility registry is complete and internally consistent."