#!/usr/bin/env bash
#=== HELP START ===
# install-pandoc.sh – Installs the Pandoc binary
#
# Usage:
#   sudo ./install-pandoc.sh [options] [<version>]
#
# Options:
#   -a, --arch <amd64|arm64>  Target architecture (default: auto-detected)
#   -d, --dir  <path>         Installation directory (default: /usr/local/bin)
#   -n, --dry-run             Download and verify, but DO NOT install
#   -h, --help                Show this help message
#
# Arguments:
#   <version>                 Pandoc version to install (default: latest)
#
# Behaviour:
#   • If pandoc is already in PATH and no version was requested, the script exits.
#   • If a specific version was requested, the installed version is only upgraded if it differs.
#=== HELP END ===
set -euo pipefail

REPO="jgm/pandoc"

# ───────────────────────────────────────────────
# Defaults
INSTALL_DIR_DEFAULT="/usr/local/bin"
INSTALL_DIR="$INSTALL_DIR_DEFAULT"
ARCH_INPUT=""
VERSION="latest"
DRY_RUN=false
USER_VERSION_SPECIFIED=false
# ───────────────────────────────────────────────

# 0 Help function
show_help() {
  sed -n '/^#=== HELP START ===/,/^#=== HELP END ===/ {
    /^#=== HELP START ===/d
    /^#=== HELP END ===/d
    s/^#//
    p
  }' "$0"
}

# 1 Parse options
POSITIONAL=()
while [[ $# -gt 0 ]]; do
  case "$1" in
    -h|--help) show_help; exit 0 ;;
    -n|--dry-run) DRY_RUN=true; shift ;;
    -a|--arch)
      [[ $# -lt 2 ]] && { echo "❌ Option $1 requires an argument"; exit 1; }
      ARCH_INPUT="$2"; shift 2 ;;
    -d|--dir)
      [[ $# -lt 2 ]] && { echo "❌ Option $1 requires an argument"; exit 1; }
      INSTALL_DIR="$2"; shift 2 ;;
    *) POSITIONAL+=("$1"); shift ;;
  esac
done
if [[ ${#POSITIONAL[@]} -gt 0 ]]; then
  VERSION="${POSITIONAL[0]}"
  USER_VERSION_SPECIFIED=true
fi

# 2 Detect / normalize architecture
detect_arch() {
  case "$(uname -m)" in
    x86_64) echo "linux-amd64" ;;
    aarch64|arm64) echo "linux-arm64" ;;
    *) echo "unsupported" ;;
  esac
}

ARCH_TAG=""
if [[ -n "$ARCH_INPUT" ]]; then
  case "$ARCH_INPUT" in
    amd64|linux-amd64) ARCH_TAG="linux-amd64" ;;
    arm64|aarch64|linux-arm64) ARCH_TAG="linux-arm64" ;;
    *) echo "❌ Unknown architecture: $ARCH_INPUT"; exit 1 ;;
  esac
else
  ARCH_TAG=$(detect_arch)
  if [[ "$ARCH_TAG" == "unsupported" ]]; then
    echo "❌ Automatic architecture detection failed. Please use -a."
    exit 1
  fi
fi

# 3 Pre-check existing installation
if command -v pandoc >/dev/null; then
  INSTALLED_PATH=$(command -v pandoc)
  INSTALLED_VER=$(pandoc -v | head -n1 | awk '{print $2}')
  if ! $USER_VERSION_SPECIFIED; then
    echo "✅ pandoc already present at ${INSTALLED_PATH} (version ${INSTALLED_VER}) – nothing to do."
    exit 0
  else
    if [[ "$INSTALLED_VER" == "$VERSION" ]]; then
      echo "✅ pandoc ${INSTALLED_VER} already installed – requested version matches."
      exit 0
    else
      echo "ℹ️  pandoc ${INSTALLED_VER} installed, upgrading to ${VERSION}..."
    fi
  fi
fi

# 4 Check required tools
need() { command -v "$1" >/dev/null || { echo "$1 is missing"; exit 1; }; }
need curl; need tar; need grep; need sed; need awk; need jq

# 5 Fetch release info
if [[ "$VERSION" == "latest" ]]; then
  API_URL="https://api.github.com/repos/${REPO}/releases/latest"
else
  API_URL="https://api.github.com/repos/${REPO}/releases/tags/${VERSION}"
fi

echo "🔍 Fetching release info (${API_URL})…"
JSON=$(curl -fsSL "$API_URL") || { echo "❌ Failed to fetch release info"; exit 1; }

VERSION=$(jq -r '.tag_name' <<< "$JSON") || { echo "❌ Could not extract version"; exit 1; }

ASSET_URL=$(jq -r '.assets[]?.browser_download_url' <<< "$JSON" |
  grep -E "pandoc-.*-${ARCH_TAG}\.tar\.gz$" | head -n1)

[[ -z "$ASSET_URL" ]] && { echo "❌ Matching asset not found for architecture ${ARCH_TAG}"; exit 1; }

ASSET_FILE=$(basename "$ASSET_URL")
echo "📦 Downloading pandoc ${VERSION} (${ASSET_FILE}) …"
TMP=$(mktemp -d)
curl -#L -o "${TMP}/${ASSET_FILE}" "$ASSET_URL"

# 6 Extract
tar -C "$TMP" -xzf "${TMP}/${ASSET_FILE}"

# 7 Locate binary
BIN_PATH=$(find "$TMP" -type f -name pandoc -perm -u+x | head -n1)
[[ -z "$BIN_PATH" ]] && { echo "❌ Binary not found"; exit 1; }

# 8 Install / Dry-run
if $DRY_RUN; then
  echo "🧪 Dry-run: verified pandoc binary at ${BIN_PATH}"
  echo "ℹ️  Would install to: ${INSTALL_DIR}/pandoc (sudo install -m755 …)"
  echo "✅ pandoc $("$BIN_PATH" -v | head -n1) would be installed successfully"
else
  sudo install -m755 "$BIN_PATH" "${INSTALL_DIR}/pandoc"
  echo "✅ pandoc $(pandoc -v | head -n1) installed in ${INSTALL_DIR}"
fi