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

# REPLACE THESE: this is the identity I want in rewritten commits
NEW_NAME="Your Name"
NEW_EMAIL="you@example.com"

URL=""
OLD_EMAILS=""
OLD_NAMES=""
AUTO_CLONE=false
CLONE_DIR=""

usage() {
  cat <<EOF
Usage:
  git-commit-update --url <URL> [--email <old1,old2,...>] [--name <old1,old2,...>] [--auto-clone] [--dir <path>]
  git-commit-update -u <URL>   [-e <old1,old2,...>]      [-n <old1,old2,...>]      [-c]           [-d <path>]

What it does:
  - Rewrites commit author/committer identities across the repo history:
      * any email in --email becomes: \$NEW_EMAIL
      * any name  in --name  becomes: \$NEW_NAME
  - Pushes branches and tags (force + prune), no PR/internal refs.

Generic examples:
  git-commit-update -u https://git.example.com/user/repo.git \\
    -e "old-email@example.com,old-alias@example.org" \\
    -n "Old Name,Another Old Name"

  git-commit-update -u "ssh://git@git.example.com:2222/user/repo.git" -c
EOF
}

# Parse args
while [[ $# -gt 0 ]]; do
  case "$1" in
    --url|-u)    URL="${2:-}"; shift 2;;
    --email|-e)  OLD_EMAILS="${2:-}"; shift 2;;
    --name|-n)   OLD_NAMES="${2:-}"; shift 2;;
    --auto-clone|-c) AUTO_CLONE=true; shift 1;;
    --dir|-d)    CLONE_DIR="${2:-}"; shift 2;;
    -h|--help)   usage; exit 0;;
    *) echo "Unknown arg: $1"; usage; exit 1;;
  esac
done

[[ -z "$URL" ]] && { echo "ERROR: --url is required"; usage; exit 1; }

# I need git-filter-repo; if missing on Arch, I install it, else ask the user to install.
if ! command -v git-filter-repo >/dev/null 2>&1; then
  if command -v pacman >/dev/null 2>&1; then
    echo "Installing git-filter-repo via pacman..."
    sudo pacman -S --needed --noconfirm git-filter-repo
  else
    echo "ERROR: git-filter-repo not found. Install it and re-run."
    echo "      https://github.com/newren/git-filter-repo"
    exit 1
  fi
fi

cleanup() { :; }
WORKDIR=""

# If I pass -c/--auto-clone, I work in a mirror clone (safe for rewriting everything)
if "$AUTO_CLONE"; then
  if [[ -n "$CLONE_DIR" ]]; then
    WORKDIR="$CLONE_DIR"
    mkdir -p "$WORKDIR"
    echo "Cloning (mirror) into: $WORKDIR"
  else
    WORKDIR="$(mktemp -d -t gitupd.XXXXXX)"
    echo "Cloning (mirror) into temp dir: $WORKDIR"
    cleanup() { rm -rf "$WORKDIR"; }
    trap cleanup EXIT
  fi
  git clone --mirror "$URL" "$WORKDIR"
  cd "$WORKDIR"
else
  # Otherwise I expect to be inside an existing Git worktree
  if ! git rev-parse --is-inside-work-tree >/dev/null 2>&1; then
    echo "ERROR: Not inside a Git repository. Use --auto-clone or cd into a repo."
    exit 1
  fi
fi

# Helper: turn "a,b,c" into a Python bytes set: {b"a",b"b",b"c"}
to_py_set() {
  local csv="${1:-}"
  if [[ -z "$csv" ]]; then
    printf 'set()'
  else
    awk -v RS=',' '
      { gsub(/^[ \t\r\n]+|[ \t\r\n]+$/,"",$0); if (length($0)) printf "b\"%s\",", $0 }
    ' <<<"$csv" | sed 's/,$//' | awk '{ printf "{%s}", $0 }'
  fi
}

EMAIL_SET=$(to_py_set "$OLD_EMAILS")
NAME_SET=$(to_py_set "$OLD_NAMES")

EMAIL_CB=()
NAME_CB=()
if [[ "$EMAIL_SET" != "set()" ]]; then
  EMAIL_CB=( --email-callback "return b\"${NEW_EMAIL}\" if email in ${EMAIL_SET} else email" )
  echo "Rewriting these emails -> ${NEW_EMAIL}: $OLD_EMAILS"
fi
if [[ "$NAME_SET" != "set()" ]]; then
  NAME_CB=( --name-callback  "return b\"${NEW_NAME}\"  if name  in ${NAME_SET}  else name" )
  echo "Rewriting these names  -> ${NEW_NAME}:  $OLD_NAMES"
fi

if [[ ${#EMAIL_CB[@]} -eq 0 && ${#NAME_CB[@]} -eq 0 ]]; then
  echo "Nothing to rewrite (no --email/--name provided). Exiting."
  exit 0
fi

# I fetch before rewriting so leases/refs are current
git fetch --all --tags --prune

# I always drop a safety tag I can roll back to
TAG="pre-rewrite-$(date +%Y%m%d-%H%M%S)"
git tag "$TAG" || true
echo "Created safety tag: $TAG"

echo "Running git-filter-repo..."
git filter-repo --force "${EMAIL_CB[@]}" "${NAME_CB[@]}"

# git-filter-repo may remove 'origin'; I make sure it points to the requested URL
if git remote get-url origin >/dev/null 2>&1; then
  git remote set-url origin "$URL"
else
  git remote add origin "$URL"
fi

# I push only branches and tags (no PR/internal refs), with force + prune
echo "Pushing branches and tags (force + prune)..."
git push --force --prune origin 'refs/heads/*:refs/heads/*'
git push --force --prune origin 'refs/tags/*:refs/tags/*'

echo "Done. Current unique identities:"
git log --all --pretty='%an <%ae>' | sort -u

echo
echo "Notes:"
echo "- If the push is rejected, temporarily allow force-push on protected branches on the server, then re-protect."
echo "- For HTTPS, most servers require a Personal Access Token as the password."