#!/usr/bin/env bash
# refresh-patches.sh — regenerate patches/ from what the fork actually changed.
#
# Since core is vendored, `patches/` is no longer how the build works — it is
# documentation. It answers the question anyone auditing this fork asks first:
# *what exactly did you change inside WordPress?* A directory of readable
# diffs answers that in a minute; `git log wordpress/` does not, because it is
# mostly upstream imports.
#
# Documentation that is generated stays true. Documentation that is maintained
# by hand drifts, and a stale record of a fork's core diff is worse than none,
# because people trust it.
#
#   tools/refresh-patches.sh          # rewrite patches/ from the tree
#   tools/refresh-patches.sh --check  # fail if it would change anything (CI)

set -euo pipefail

here="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
repo="$(git -C "$here" rev-parse --show-toplevel)"
# Ask git where we are rather than subtracting paths: on Windows
# --show-toplevel answers "D:/..." while $PWD is "/d/...", and the
# subtraction silently leaves an absolute path behind.
prefix="$(cd "$here" && git rev-parse --show-prefix)wordpress"
UPSTREAM_BRANCH="sirius-press/wordpress-upstream"
CHECK=0

for arg in "$@"; do
  case "$arg" in
    --check) CHECK=1 ;;
    *) echo "unknown option: $arg" >&2; exit 2 ;;
  esac
done

say() { printf '\033[1m→\033[0m %s\n' "$*"; }
die() { printf '\033[31merror:\033[0m %s\n' "$*" >&2; exit 1; }

git -C "$repo" rev-parse --verify --quiet "$UPSTREAM_BRANCH" >/dev/null \
  || die "the branch $UPSTREAM_BRANCH is missing; there is nothing to diff against."

# shellcheck source=wordpress.lock
source "$here/tools/wordpress.lock"

staging="$here/dist/.patch-refresh"
rm -rf "$staging"
mkdir -p "$staging"

say "comparing ${prefix}/ against pristine WordPress ${WP_VERSION}"

# Every path that differs between the vendored tree and the pristine import.
#
# Compared tree to tree, not commit to commit: the upstream branch keeps
# WordPress at its root while the subtree keeps it under a prefix, so a
# plain `git diff BRANCH HEAD -- <prefix>` compares two different path
# spaces and reports the whole distribution as added.
UPSTREAM_TREE="${UPSTREAM_BRANCH}^{tree}"
VENDORED_TREE="HEAD:${prefix}"

mapfile -t changed < <(
  git -C "$repo" diff --name-only "$UPSTREAM_TREE" "$VENDORED_TREE"
)

if [ ${#changed[@]} -eq 0 ]; then
  say "the fork changes nothing in core — writing an empty series"
fi

index=0
for file in "${changed[@]}"; do
  [ -n "$file" ] || continue
  index=$((index + 1))
  slug="$(echo "$file" | tr '/.' '--' | tr -cd 'A-Za-z0-9-')"
  out="$staging/$(printf '%04d' "$index")-${slug}.patch"

  {
    echo "Subject: [PATCH] ${file}"
    echo
    echo "The fork's change to this file, regenerated by tools/refresh-patches.sh."
    echo "It is a record, not the mechanism: core is vendored under wordpress/ and"
    echo "this diff is what distinguishes it from pristine upstream."
    echo
    echo "Applies to: WordPress ${WP_VERSION}"
    git -C "$repo" diff "$UPSTREAM_TREE" "$VENDORED_TREE" -- "$file" | tail -n +3
  } > "$out"
done

if [ "$CHECK" -eq 1 ]; then
  if diff -rq "$here/patches" "$staging" >/dev/null 2>&1; then
    say "patches/ matches the tree"
    rm -rf "$staging"
    exit 0
  fi
  diff -ru "$here/patches" "$staging" || true
  rm -rf "$staging"
  die "patches/ is out of date. Run tools/refresh-patches.sh and commit the result."
fi

rm -f "$here/patches"/*.patch
if [ "$index" -gt 0 ]; then
  cp "$staging"/*.patch "$here/patches/"
fi
rm -rf "$staging"

say "wrote ${index} patch file(s) describing the fork's core diff"
for f in "$here/patches"/*.patch; do
  [ -e "$f" ] || continue
  printf '   %s (%s lines)\n' "$(basename "$f")" "$(grep -c '' "$f")"
done