#!/bin/bash
#-----------------------------------------------------------------------------
#
# pkgchangelog
#
# Pkgchangelog generates changelogs of packages pending for being upgraded.
# It provides a single changelog for all packages sharing the same source
# package and therefore have the same changelog.
#
# A package changelog is generated between the installed version and the
# version pending for being upgraded. If there are multiple versions
# of the same package installed on the system, then the newest package is
# used as the source version. However it's also possible to specify a
# specific version or architecture as the source package.
#
#-----------------------------------------------------------------------------
#
# Author: (c) 2019,2024 - Invoca Systems <simon.matter@invoca.ch>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by the
# Free Software Foundation, either version 2 of the license or, at your
# option, any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, see <http://www.gnu.org/licenses/>.
#
#-----------------------------------------------------------------------------

# Do not set `$VERSION' if it is already set in library mode
if ! (( ${VERSION+1} )); then
  declare -r VERSION="2.2.29"
fi

# Check BASH version
declare -i MINMAJOR=3
if (( BASH_VERSINFO[0] < MINMAJOR )); then
  echo "Error: unable to run with bash version < ${MINMAJOR}, exiting" >&2
  exit 1
fi
unset -v MINMAJOR

# Check that needed binaries exist
pkg_check_bin() {
  while (( $# )); do
    if ! command -v "$1" > /dev/null 2>&1; then
      echo "Error: ${FUNCNAME[0]}() binary \`${1}' not found or not executable" >&2
      exit 1
    fi
    shift
  done
}

# Produce changelog from the source version to the upgradable version
# for the selected package.
#
# In case of an error, RPM still sends messages to STDOUT and only sets an
# error as exit level. Therefore we read RPM data only in case there was no
# error. Some DNF/YUM tools like `repoquery' have a `--quiet' switch which
# works as expected, others like `yumdownloader' behave like RPM.
rpm_changelog() {
  local RPMPKG="$1"
  local NAME=
  local VEROLD=
  local ARCH=
  local SRCNAME=
  local VERNEW=
  local MATCH
  local URL=
  local CHLOG=
  local QUERY
  local RES
  local -i HEADER
  local -i NOCHLOG

  if ! [[ "$RPMPKG" ]]; then
    echo "Error: ${FUNCNAME[0]}() no package name given" >&2
    return 1
  fi

  QUERY="%{name} %{version}-%{release} %{arch} %{sourcerpm}\n"
  IFS=" " read -rs NAME VEROLD ARCH SRCNAME < <(RES="$(rpm -q --qf "$QUERY" "$RPMPKG")" && echo "$RES" | tail -n 1)
  SRCNAME="${SRCNAME%.src.rpm}"
  SRCNAME="${SRCNAME%-*}"
  SRCNAME="${SRCNAME%-*}"
  if ! [[ "$NAME" ]]; then
    echo "Error: ${FUNCNAME[0]}() \$NAME no \`${QUERY}' found for \`${RPMPKG}'" >&2
    return 1
  elif ! [[ "$VEROLD" ]]; then
    echo "Error: ${FUNCNAME[0]}() \$VEROLD no \`${QUERY}' found for \`${RPMPKG}'" >&2
    return 1
  elif ! [[ "$ARCH" ]]; then
    echo "Error: ${FUNCNAME[0]}() \$ARCH no \`${QUERY}' found for \`${RPMPKG}'" >&2
    return 1
  elif ! [[ "$SRCNAME" ]]; then
    echo "Error: ${FUNCNAME[0]}() \$SRCNAME no \`${QUERY}' found for \`${RPMPKG}'" >&2
    return 1
  fi

  # Try using the cache file to save a lot of time
  if [[ -s "$PKGLIST" ]]; then
    IFS=" " read -rs _ VERNEW _ < <(grep -se "^${NAME}\.${ARCH}" "$PKGLIST")
  else
    VERNEW=
  fi
  if ! [[ "$VERNEW" ]]; then
    if [[ "$PKG_PROG" == "yum" ]]; then
      QUERY="updates"
    else
      QUERY="--upgrades"
    fi
    IFS=" " read -rs _ VERNEW _ < <(RES="$("$PKG_PROG" --quiet list "$QUERY" "${NAME}.${ARCH}")" && echo "$RES" | tail -n 1)
  fi
  # Strip EPOCH from version
  VERNEW="${VERNEW#*:}"
  if ! [[ "$VERNEW" ]]; then
    echo "Error: ${FUNCNAME[0]}() \$VERNEW no \`${QUERY}' found for \`${NAME}.${ARCH}'" >&2
    return 1
  fi

  # We do search for matching changelog entries beginning with `*'
  MATCH="$(rpm -q --changelog "${NAME}-${VEROLD}.${ARCH}" | grep -e "^\*")"
  if ! [[ "$MATCH" ]]; then
    echo "Error: ${FUNCNAME[0]}() \$MATCH no changelog found for \`${NAME}-${VEROLD}.${ARCH}'" >&2
    return 1
  fi

  IFS= read -rs URL < <(RES="$(yumdownloader --quiet --urls "${NAME}-${VERNEW}.${ARCH}")" && echo "$RES" | tail -n 1)
  if ! [[ "$URL" ]]; then
    echo "Error: ${FUNCNAME[0]}() \$URL no url found for \`${NAME}-${VERNEW}.${ARCH}'" >&2
    return 1
  fi

  if [[ "$VEROLD" == "$VERNEW" ]]; then
    echo "Error: ${FUNCNAME[0]}() no upgradable version found for \`${NAME}-${VEROLD}.${ARCH}'" >&2
    return 1
  fi

  HEADER=1
  NOCHLOG=1
  while IFS= read -rs CHLOG; do

    if (( HEADER )); then
      HEADER=0
      echo "Changelog between source versions:"
      echo "   --> ${SRCNAME}-${VERNEW}"
      echo "  <--  ${SRCNAME}-${VEROLD}"
      echo
    fi

    if [[ "$CHLOG" =~ ^Changelog ]]; then
      continue
    elif [[ "$CHLOG" =~ ^\\* ]]; then
      if [[ "$MATCH" != "${MATCH/"$CHLOG"}" ]]; then
        break
      else
	NOCHLOG=0
      fi
    fi

    echo "$CHLOG"
  done < <(rpm -qp --changelog "$URL" 2> /dev/null ||
    echo "Error: ${FUNCNAME[0]}() reading changelog for \`${NAME}-${VERNEW}.${ARCH}' failed" >&2)

  # Changelogs were processed but there were no changes detected
  if (( NOCHLOG )); then
    echo "(none)"
    echo
  fi

  return $HEADER
}

# Read list of packages from parameters and from STDIN and process them
rpm_batchmode() {
  local ITEM=
  local RPMPKG=
  local RPMCHLOG
  local QUERY
  local SRCNAME=
  local LASTSRC
  local SHARED=
  local PKG
  local RES
  {
    for ITEM in $@; do
      if [[ "$ITEM" != "-s" ]] && [[ "$ITEM" != "--stdin" ]]; then
        echo "$ITEM"
      else
        while read -rs ITEM SHARED; do
          echo "$ITEM"
        done
      fi
    done
  } |
  \
  while read -rs RPMPKG SHARED; do
    if ! [[ "$RPMPKG" ]]; then
      continue
    elif [[ "$RPMPKG" != "${RPMPKG%.src}" ]]; then
      echo "Error: ${FUNCNAME[0]}() query for source package \`${RPMPKG}' not supported" >&2
      continue
    fi
    QUERY="%{sourcerpm}\n"
    IFS=" " read -rs SRCNAME < <(RES="$(rpm -q --qf "$QUERY" "$RPMPKG")" && echo "$RES" | tail -n 1)
    SRCNAME="${SRCNAME%.src.rpm}"
    SRCNAME="${SRCNAME%-*}"
    SRCNAME="${SRCNAME%-*}"
    if ! [[ "$SRCNAME" ]]; then
      echo "Error: ${FUNCNAME[0]}() \$SRCNAME no \`${QUERY}' found for \`${RPMPKG}'" >&2
      continue
    fi
    echo "$SRCNAME $RPMPKG"
  done |
  \
  sort -bdu |
  \
  {
    LASTSRC=
    while read -rs SRCNAME RPMPKG; do
      if [[ "$SRCNAME" != "$LASTSRC" ]]; then
        if [[ "$LASTSRC" ]]; then
          echo
        fi
        echo -n "$SRCNAME"
        LASTSRC="$SRCNAME"
      fi
      echo -n " $RPMPKG"
    done
    echo
  } |
  \
  while read -rs SRCNAME RPMPKG SHARED; do
    if ! [[ "$RPMPKG" ]]; then
      continue
    fi
    echo "$LINESEP"
    echo
    echo "Packages sharing source \`${SRCNAME}':"
    # Out of the packages sharing the same `$SRCNAME', `$RPMPKG' is the first
    # package in alphabetical order. In certain situations, we should not use
    # this package to generate the changelog as can be seen below.
    RPMCHLOG="$RPMPKG"
    for PKG in $RPMPKG $SHARED; do
      echo "  $PKG"
      echo "    $(rpm -q --qf "%{summary}" "$PKG")"
      # If the `$SRCNAME' package is installed, use it to produce the changelog.
      # On EL9, there is `bpftool-7.2.0-362.18.1.el9_3' built from
      # `kernel-5.14.0-362.18.1.el9_3'. Wthout this fix, the changelog would
      # show version `7.2.0-362.18.1.el9_3' instead of `5.14.0-362.18.1.el9_3'!
      if [[ "$PKG" == "$SRCNAME" ]]; then
        RPMCHLOG="$SRCNAME"
      fi
    done
    echo
    rpm_changelog "$RPMCHLOG"
  done
}

pkg_help() {
  cat << EOF
Usage: $BASENAME [OPTION] <PACKAGE> [<PACKAGE>]...

Options:
  -s, --stdin     reads a list of packages from STDIN
  -V, --version   show version information and exit
  -h, --help      display this help and exit

Examples:
pkgchangelog kernel-3.10.0-1127.el7.x86_64
yum --quiet check-update | pkgchangelog --stdin
pkgchangelog --stdin postfix spamassassin cyrus-imapd \\
  bind < <(dnf --quiet check-upgrade | grep -Ee "kernel|glibc")
EOF
}

pkg_version() {
  echo "$BASENAME version $VERSION"
}

# Main program starts here

# Option `-l' means we're in library mode and don't execute anything
if [[ "$1" == "-l" ]]; then
  if ! [[ "$LINESEP" ]]; then
    declare LINESEP="$(printf "=%.0s" {1..80})"
  fi
  return 0
fi

# Treat unset variables and parameters other than the special
# parameters `@' and `*' as an error when performing parameter expansion.
set -o nounset

# Detect line width of STDOUT, defaults to 80 if not running in a terminal
declare -i WIDTH=80
if [[ -t 1 ]]; then
  declare STRING=
  exec 3> /dev/stdout
  read -rs _ STRING < <(stty -F /dev/fd/3 size 2> /dev/null)
  exec 3>&-
  if [[ "$STRING" ]]; then
    WIDTH=$STRING
  fi
  unset -v STRING
fi

# Set sane defaults
declare -x LC_ALL="C"
declare BASENAME="${0##*/}"
declare LINESEP="$(eval printf "=%.0s" "{1..${WIDTH}}")"
declare OPT

for OPT in "$@"; do
  case "$OPT" in
    "-V"|"--version")
      pkg_version
      exit 0
      ;;
    "-h"|"--help")
      pkg_help
      exit 0
      ;;
  esac
done

if ! (( $# )); then
  pkg_version
  pkg_help >&2
  exit 1
else
  # Variables already set in library mode
  declare -r PKGLIST="/var/cache/pkgmonitor/pkglist"
  declare -r PKG_PROG="$(command -v "dnf" > /dev/null 2>&1 && echo "dnf" || echo "yum")"
  pkg_check_bin repoquery yumdownloader "$PKG_PROG"
  rpm_batchmode "$@"
fi