#!/bin/sh

# Copyright (c) 2000-2023, Board of Trustees of Leland Stanford Jr. University
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# 1. Redistributions of source code must retain the above copyright notice,
# this list of conditions and the following disclaimer.
#
# 2. Redistributions in binary form must reproduce the above copyright notice,
# this list of conditions and the following disclaimer in the documentation
# and/or other materials provided with the distribution.
#
# 3. Neither the name of the copyright holder nor the names of its contributors
# may be used to endorse or promote products derived from this software without
# specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.

#
# Version
#

VERSION='1.4.0'

#
# Program name
#

_0='lockss-downloader'

#
# Constants
#

DEFAULT_GIT_BRANCH='master'
DEFAULT_GIT_PROJECT='https://github.com/lockss/lockss-installer'

#
# Fatal
# $1: optional message
#
Fatal()
{
  if [ -n "${1}" ] ; then
    echo "${_0}: error: ${1}" >&2
  fi
  exit 1
}

#
# Graceful
#
Graceful()
{
  exit 0
}

#
# Check_Root
#
Check_Root()
{
  if [ "$(id -u)" = '0' ] ; then
    Fatal 'cannot be run as root'
  fi
}


#
# Create_Download_Dir
#
Create_Download_Dir()
{
  if [ -d "${DOWNLOAD_DIR}" ] ; then
    return
  fi
  if [ -e "${DOWNLOAD_DIR}" ] ; then
    Fatal "${DOWNLOAD_DIR} already exists but is not a directory"
  fi
  mkdir -p "${DOWNLOAD_DIR}" || Fatal "could not create ${DOWNLOAD_DIR}"
}

#
# Display_Summary
#
Display_Summary()
{
  if [ "${QUIET}" != 'true' ] ; then
    case "${GIT_BRANCH}${GIT_COMMIT}${GIT_TAG}" in
      "${GIT_BRANCH}") _s="branch: ${GIT_BRANCH}" ;;
      "${GIT_COMMIT}") _s="commit: ${GIT_COMMIT}" ;;
      "${GIT_TAG}") _s="tag: ${GIT_TAG}" ;;
      *) Fatal 'invalid Git state' ;; # shouldn't happen
    esac
    echo "https://github.com/${GIT_PROJECT} downloaded into ${DOWNLOAD_DIR} (${_s})"
  fi
}

#
# Download_From_Github
#
Download_From_Github()
{
  case "${GIT_BRANCH}${GIT_COMMIT}${GIT_TAG}" in
    "${GIT_BRANCH}") _url="https://github.com/${GIT_PROJECT}/archive/refs/heads/${GIT_BRANCH}" ;;
    "${GIT_COMMIT}") _url="https://github.com/${GIT_PROJECT}/archive/${GIT_COMMIT}" ;;
    "${GIT_TAG}") _url="https://github.com/${GIT_PROJECT}/archive/refs/tags/${GIT_TAG}" ;;
    *) Fatal 'unknown Git reference' ;; # shouldn't happen
  esac
  case "${ARCHIVER}" in
    gtar|tar) _url="${_url}.tar.gz" ;;
    *) Fatal "unknown archiver: ${ARCHIVER}" ;; # shouldn't happen
  esac
  ( case "${DOWNLOADER}" in
      curl) curl -sSfL "${_url}" ;;
      wget) wget -qO- "${_url}" ;;
      http) http -qd "${_url}" ;;
      *) Fatal "unknown downloader: ${DOWNLOADER}" ;; # shouldn't happen
    esac \
      | case "${ARCHIVER}" in
          gtar|tar) "$ARCHIVER" xzf - --directory="${DOWNLOAD_DIR}" --strip-components=1 ;;
          *) Fatal "unknown archiver: ${ARCHIVER}" ;; # shouldn't happen ;;
        esac ) || Fatal "could not download and extract ${_url}"
}

#
# Print_Help
#
Print_Help()
{
  cat <<MyEOF
${_0} version ${VERSION}

Usage:

  ${_0} [--curl|--httpie|--wget] [--download-dir=DIR] [--git-branch=BRA|
        --git-commit=COM|--git-tag=TAG] [--quiet] [PROJECT]
  ${_0} --version
  ${_0} --help

Argument:

  PROJECT
        GitHub project reference (default: ${DEFAULT_GIT_PROJECT};
        format: https://github.com/X/Y or https://github.com/X/Y.git or
        git@github.com:X/Y or git@github.com:X/Y.git or X/Y where GitHub is
        implied)

Options:

  --help, -help, -h
        display this message and exit
  --quiet, -quiet, -q
        produce no output unless an error occurs
  --version, -version
        display this program's version number and exit

Git Tree Options:

  --git-branch=BRA, --git-branch BRA, -git-branch BRA, -b BRA
        use Git branch BRA (default: ${DEFAULT_GIT_BRANCH})
  --git-commit=COM, --git-commit COM, -git-commit COM, -c COM
        use Git commit COM instead of a Git branch
  --git-tag=TAG, --git-tag TAG, -git-tag TAG, -t TAG
        use Git tag TAG instead of a Git branch

Directory Options:

  --download-dir=DIR, --download-dir DIR, -download-dir DIR, -d DIR
        download into DIR (default: \$HOME/<Y> where <Y> is derived from the
        GitHub project reference https://github.com/X/Y)

Fetch Options:

  --curl, -curl, -C
        force the use of Curl
  --httpie, -httpie, -H
        force the use of HTTPie
  --wget, -wget, -W
        force the use of Wget
MyEOF
}

#
# Parse_Command_Line
# Must be called with "$@"
#
Parse_Command_Line()
{
  while [ $# -gt 0 ] ; do
    case "${1}" in

      --curl|-curl|-C) CURL='true' ; shift ;;

      --download-dir=*) Set_Download_Dir "${1#*=}" ; shift ;;
      --download-dir|-download-dir|-d) Set_Download_Dir "${2}" ; shift ; shift ;;

      --git-branch=*) Set_Git_Branch "${1#*=}" ; shift ;;
      --git-branch|-git-branch|-b) Set_Git_Branch "${2}" ; shift ; shift ;;

      --git-commit=*) Set_Git_Commit "${1#*=}" ; shift ;;
      --git-commit|-git-commit|-c) Set_Git_Commit "${2}" ; shift ; shift ;;

      --git-tag=*) Set_Git_Tag "${1#*=}" ; shift ;;
      --git-tag|-git-tag|-t) Set_Git_Tag "${2}" ; shift ; shift ;;

      --help|-help|-h) Print_Help ; Graceful ;;
        
      --httpie|-httpie|-H) HTTPIE='true' ; shift ;;

      --quiet|-quiet|-q) QUIET='true' ; shift ;;

      --version|-version) echo "${VERSION}" ; Graceful ;;

      --wget|-wget|-W) WGET='true' ; shift ;;

      -*) Fatal "unknown option: ${1}" ;;

      *) Set_Git_Project "${1}" ; shift ;;

    esac
  done
  
  case "${CURL}${HTTPIE}${WGET}" in
    ''|"${CURL}"|"${HTTPIE}"|"${WGET}") ;;
    *) Fatal 'at most one of --curl, --httpie, --wget can be used' ;;
  esac

  case "${GIT_BRANCH}${GIT_COMMIT}${GIT_TAG}" in
    '') GIT_BRANCH="${DEFAULT_GIT_BRANCH}" ;;
    "${GIT_BRANCH}"|"${GIT_COMMIT}"|"${GIT_TAG}") ;;
    *) Fatal 'at most one of --git-branch, --git-commit, --git-tag can be used' ;;
  esac

  # Must be before DOWNLOAD_DIR section
  if [ -z "${GIT_PROJECT}" ] ; then
    Set_Git_Project "${DEFAULT_GIT_PROJECT}"
  fi

  if [ -z "${DOWNLOAD_DIR}" ] ; then
    Set_Download_Dir "${HOME}/$(basename "${GIT_PROJECT}")"
  fi

}

#
# Set_Archiver
#
Set_Archiver()
{
  if [ "$(uname -s)" = 'Darwin' ] && command -v gtar > /dev/null ; then
    ARCHIVER='gtar'
  elif command -v tar > /dev/null ; then
    ARCHIVER='tar'
  fi
  if [ -z "${ARCHIVER}" ] ; then
    Fatal 'no tar (or gtar) on the PATH'
  fi
}

#
# Set_Download_Dir
# $1: directory path
#
Set_Download_Dir()
{
  if [ -z "${1}" ] ; then
    Fatal '--download-dir: empty directory path'
  fi
  if [ -z "${DOWNLOAD_DIR}" ] ; then
    DOWNLOAD_DIR="${1}"
  elif [ "${1}" != "${DOWNLOAD_DIR}" ] ; then
    Fatal "--download-dir: ${1} conflicts with ${DOWNLOAD_DIR}"
  fi
}

#
# Set_Downloader
# $1: executable
#
Set_Downloader()
{
  case "${CURL}${HTTPIE}${WGET}" in
    '')
      for _d in curl wget http ; do
        if command -v "${_d}" > /dev/null ; then
          DOWNLOADER="${_d}"
          break
        fi
      done
      if [ -z "${DOWNLOADER}" ] ; then
        Fatal 'at least one of curl, wget, http must be on the PATH'
      fi
      ;;
    "${CURL}")
      if command -v curl > /dev/null ; then
        DOWNLOADER='curl'
      else
        Fatal '--curl: curl must be on the PATH'
      fi
      ;;
    "${HTTPIE}")
      if command -v http > /dev/null ; then
        DOWNLOADER='http'
      else
        Fatal '--httpie: http must be on the PATH'
      fi
      ;;
    "${WGET}")
      if command -v wget > /dev/null ; then
        DOWNLOADER='wget'
      else
        Fatal '--wget: wget must be on the PATH'
      fi
      ;;
    *)
      Fatal 'invalid downloader'
      ;; # shouldn't happen
  esac
}

#
# Set_Git_Branch
# $1: branch name
#
Set_Git_Branch()
{
  if [ -z "${1}" ] ; then
    Fatal '--git-branch: empty branch name'
  fi
  if [ -z "${GIT_BRANCH}" ] ; then
    GIT_BRANCH="${1}"
  elif [ "${1}" != "${GIT_BRANCH}" ] ; then
    Fatal "--git-branch: ${1} conflicts with ${GIT_BRANCH}"
  fi
}

#
# Set_Git_Commit
# $1: commit name
#
Set_Git_Commit()
{
  if [ -z "${1}" ] ; then
    Fatal '--git-commit: empty commit name'
  fi
  if [ -z "${GIT_COMMIT}" ] ; then
    GIT_COMMIT="${1}"
  elif [ "${1}" != "${GIT_COMMIT}" ] ; then
    Fatal "--git-commit: ${1} conflicts with ${GIT_COMMIT}"
  fi
}

#
# Set_Git_Project
# $1: project reference (foo/bar, https://github.com/foo/bar, https://github.com/foo/bar.git, git@github.com:foo/bar, git@github.com:foo/bar.git)
#
Set_Git_Project()
{
  if [ -z "${1}" ] ; then
    Fatal 'empty project reference'
  fi
  case "${1}" in
    https://github.com/*/*) _proj="${1%.git}" ; _proj="${_proj#https://github.com/}" ;;
    git@github.com:*/*) _proj="${1%.git}" ; _proj="${_proj#git@github.com:}" ;;
    */*) _proj="${1}" ;;
    *) Fatal "invalid project reference: ${1}" ;;
  esac
  if [ "${_proj%/*}/${_proj#*/}" != "${_proj}" ] ; then
    Fatal "invalid project reference: ${1}"
  fi
  if [ -z "${GIT_PROJECT}" ] ; then
    GIT_PROJECT="${_proj}"
  elif [ "${_proj}" != "${GIT_PROJECT}" ] ; then
    Fatal "${_proj} conflicts with ${GIT_PROJECT}"
  fi
}

#
# Set_Git_Tag
# $1: tag name
#
Set_Git_Tag()
{
  if [ -z "${1}" ] ; then
    Fatal '--git-tag: empty tag name'
  fi
  if [ -z "${GIT_TAG}" ] ; then
    GIT_TAG="${1}"
  elif [ "${1}" != "${GIT_TAG}" ] ; then
    Fatal "--git-tag: ${1} conflicts with ${GIT_TAG}"
  fi
}

#
# Variables
#

ARCHIVER=''
CURL=''
DOWNLOAD_DIR=''
DOWNLOADER=''
GIT_BRANCH=''
GIT_COMMIT=''
GIT_PROJECT=''
GIT_TAG=''
HTTPIE=''
QUIET=''
WGET=''

#
# Main
#

Parse_Command_Line "$@"
Check_Root
Set_Downloader
Set_Archiver
Create_Download_Dir
Download_From_Github
Display_Summary
Graceful