#!/usr/bin/env bash
# ─────────────────────────────────────────────────────────────
#  🌱 Git History Grafting Tool
#  Attach your rewrite branch to an existing remote's history.
#
#  Author: Owais J <https://github.com/desertthunder>
#  Updated: 2025-11-03
#
#  Description:
#    This script grafts a rewrite branch (e.g., refactor) onto
#    an existing Git remote history, preserving ancestry while
#    discarding old files.
# ─────────────────────────────────────────────────────────────
set -euo pipefail

C_BLUE=110     # cyan-blue accents
C_CYAN=117     # bright cyan
C_PURPLE=141   # icy lavender
C_GREY=249     # soft gray text
C_DIM=244      # dimmer gray
C_GREEN=78     # sea green success
C_YELLOW=179   # muted yellow warning
C_RED=203      # red error

BASE_BRANCH="main"
REMOTE=""
NEW_BRANCH=""
NON_INTERACTIVE=false

header() {
  gum style --foreground "$C_BLUE" --bold "🌱 Git History Grafting Tool"
  gum style --foreground "$C_DIM" "Attach your rewrite branch to an existing remote's history safely."
  echo
}

show_help() {
  SCRIPT_NAME=$(basename "$0")

  header

  printf "Usage:\n  %s [options]\n\n" "$SCRIPT_NAME" | gum style --foreground "$C_GREY"

  printf "Options:\n" | gum style --foreground "$C_GREY" --bold
  {
    echo "--remote <name>"
    echo "    Git remote to graft onto (e.g. origin)"
    echo
    echo "--branch <name>"
    echo "    Your local rewrite branch (e.g. refactor)"
    echo
    echo "--base <branch>"
    echo "    Base branch on the remote (default: main)"
    echo
    echo "--yes, --non-interactive"
    echo "    Skip all confirmations (CI-safe)"
    echo
    echo "-h, --help"
    echo "    Show this help message and exit"
  } | gum style --foreground "$C_DIM"

  echo
  printf "Examples:\n" | gum style --foreground "$C_GREY" --bold
  printf "  Interactive mode:\n" | gum style --foreground "$C_DIM"
  printf "    %s\n" "./$SCRIPT_NAME" | gum style --foreground "$C_CYAN"
  echo
  printf "  Non-interactive (CI):\n" | gum style --foreground "$C_DIM"
  printf "    %s --remote origin --branch refactor --base main --yes\n" "./$SCRIPT_NAME" \
    | gum style --foreground "$C_CYAN"

  echo
  printf "Theme:\n" | gum style --foreground "$C_GREY" --bold
  printf "  • Iceberg.vim-inspired — subtle cyan, lavender, and gray tones\n" \
    | gum style --foreground "$C_PURPLE"
  echo
}

while [[ $# -gt 0 ]]; do
  case "$1" in
    --remote) REMOTE="$2"; shift 2;;
    --branch) NEW_BRANCH="$2"; shift 2;;
    --base) BASE_BRANCH="$2"; shift 2;;
    --yes|--non-interactive) NON_INTERACTIVE=true; shift;;
    -h|--help) show_help; exit 0;;
    -*) echo "Unknown option: $1" >&2; exit 1;;
    *) shift;;
  esac
done

header

git rev-parse --is-inside-work-tree >/dev/null

if [ -z "$REMOTE" ]; then
  mapfile -t REMOTES < <(git remote)
  if [ ${#REMOTES[@]} -eq 0 ]; then
    gum style --foreground "$C_RED" "❌ No remotes found. Please add one (e.g., git remote add origin ...)."
    exit 1
  fi
  REMOTE=$(gum choose "${REMOTES[@]}" --header "Select the remote to graft onto:")
fi

if [ -z "$NEW_BRANCH" ]; then
  LOCAL_BRANCH=$(git branch --show-current || true)
  DEFAULT_BRANCH=${LOCAL_BRANCH:-"refactor"}
  NEW_BRANCH=$(gum input --placeholder "Enter the name of your rewrite branch" --value "$DEFAULT_BRANCH")
fi

if ! git show-ref --verify --quiet "refs/heads/$NEW_BRANCH"; then
  gum style --foreground "$C_RED" "❌ Branch '$NEW_BRANCH' not found."
  exit 1
fi

gum style --foreground "$C_BLUE" "Using remote: $REMOTE"
gum style --foreground "$C_BLUE" "Using base branch: $REMOTE/$BASE_BRANCH"
gum style --foreground "$C_BLUE" "Using rewrite branch: $NEW_BRANCH"

if [ "$NON_INTERACTIVE" = false ]; then
  gum confirm "Proceed to graft '$NEW_BRANCH' onto '$REMOTE/$BASE_BRANCH'?" || exit 0
fi

gum spin --spinner line --title "Fetching $REMOTE..." -- git fetch "$REMOTE" "$BASE_BRANCH"
gum spin --spinner line --title "Checking out $NEW_BRANCH..." -- git checkout "$NEW_BRANCH"

ROOT_COMMIT=$(git rev-list --max-parents=0 HEAD)
BASE_COMMIT=$(git rev-parse "$REMOTE/$BASE_BRANCH")

{
  echo -e "Key\tValue"
  echo -e "$(gum style --foreground "$C_PURPLE" 'Root Commit')\t$ROOT_COMMIT"
  echo -e "$(gum style --foreground "$C_PURPLE" 'Base Commit')\t$BASE_COMMIT"
} | gum table

gum spin --spinner minidot --title "Creating temporary graft..." -- \
  git replace --graft "$ROOT_COMMIT" "$BASE_COMMIT"

gum style --foreground "$C_GREEN" "✓ Graft created. Showing recent commits..."

git --no-pager log --oneline --graph --decorate -10 | gum format --theme=dark

if command -v git-filter-repo >/dev/null; then
  gum spin --spinner pulse --title "Rewriting branch '$NEW_BRANCH'..." -- \
    git filter-repo --force --refs "refs/heads/$NEW_BRANCH" --preserve-commit-hashes
else
  gum style --foreground "$C_YELLOW" "⚠ git-filter-repo not found; using slower git filter-branch"
  gum spin --spinner pulse --title "Rewriting history..." -- \
    git filter-branch -- --refs "refs/heads/$NEW_BRANCH"
fi

if git show-ref --quiet "refs/replace/$ROOT_COMMIT"; then
  git replace -d "$ROOT_COMMIT"
fi

if [ ! -d .git/refs/remotes ]; then
  gum style --foreground "$C_DIM" "Restoring remote refs..."
  git fetch --all
fi

if [ "$NON_INTERACTIVE" = true ] || gum confirm "Push '$NEW_BRANCH' to $REMOTE?"; then
  gum spin --spinner line --title "Pushing to $REMOTE..." -- \
    git push "$REMOTE" "$NEW_BRANCH" --force-with-lease
fi

gum style --foreground "$C_GREEN" "✓ Done!"
gum style --foreground "$C_DIM" "Your rewrite branch '$NEW_BRANCH' now descends from '$REMOTE/$BASE_BRANCH'."