#!/usr/bin/env bash
#
# Structurally compare, object-by-object, every member of the cat_tools
# extension in two databases: function bodies (pg_get_functiondef), view
# definitions (pg_get_viewdef), type labels/columns (enums, the one plain
# table, the one standalone composite type), comments, and ACLs. A nonempty
# diff is a bug -- the whole point of an extension UPDATE script is that it
# reaches the SAME objects a fresh install of the target version would.
#
# This generalizes a manual comparison run by hand while fixing
# https://github.com/Postgres-Extensions/cat_tools/pull/46: that PR found a
# real fresh-vs-update divergence this way (cat_tools.trigger__parse, as
# produced by the pre-0.2.2 update scripts, hardcoded `EXECUTE PROCEDURE` and
# skipped an empty-args guard that the fresh-install body had, breaking every
# trigger parse on PG11+). Committing the comparison as a script makes it a
# standing, automated check instead of something that has to be remembered
# and run by hand.
#
# USAGE: bin/structural_diff <subcommand> [args]
#
#   dump DB [EXTNAME]
#       Print the signature of every EXTNAME member object in DB (EXTNAME
#       defaults to cat_tools). Useful on its own for eyeballing one
#       database's structure, and it's what `compare` diffs under the hood.
#
#   compare DB1 DB2 [EXTNAME]
#       Dump both databases and diff them. Prints a unified diff and exits
#       non-zero if they differ; exits 0 (and prints an OK line) if
#       identical.
#
# See bin/structural_diff.sql for the query that defines "signature" (and how
# it decides which object kinds get a real structural definition vs. falling
# back to just identity/comment/ACL).
set -euo pipefail

SCRIPT_DIR=$(cd "$(dirname "$(readlink -f "$0")")" && pwd)

# ---------------------------------------------------------------------------
# Subcommand implementations
# ---------------------------------------------------------------------------

dump() {
  local db=$1 extname=${2:-cat_tools}
  psql -d "$db" -v extname="'$extname'" -f "$SCRIPT_DIR/structural_diff.sql"
}

compare() {
  local db1=$1 db2=$2 extname=${3:-cat_tools}
  # Run in a subshell so the EXIT trap (temp-file cleanup) is scoped to this
  # comparison only. A trap set with plain `trap ... RETURN` is NOT scoped to
  # the function that set it -- it re-fires on every later function return in
  # the same shell, including main()'s, by which point f1/f2 no longer exist.
  (
    f1=$(mktemp)
    f2=$(mktemp)
    trap 'rm -f "$f1" "$f2"' EXIT
    dump "$db1" "$extname" > "$f1"
    dump "$db2" "$extname" > "$f2"
    if diff -u --label "$db1" --label "$db2" "$f1" "$f2"; then
      echo "OK: '$db1' and '$db2' are structurally identical for extension '$extname'"
    else
      echo "FAIL: structural diff between '$db1' and '$db2' for extension '$extname' (see diff above) -- an update path reached objects that differ from a fresh install" >&2
      exit 1
    fi
  )
}

usage() {
  echo "usage: bin/structural_diff <subcommand> [args]" >&2
  echo "  dump DB [EXTNAME]" >&2
  echo "  compare DB1 DB2 [EXTNAME]" >&2
  exit 2
}

# Explicit subcommand dispatch on $1, matching bin/test_existing and
# bin/assert_fs_clean's convention.
main() {
  local cmd=${1:-}
  shift || true
  case "$cmd" in
    dump)    dump "$@" ;;
    compare) compare "$@" ;;
    *)       usage ;;
  esac
}

main "$@"