#!/bin/bash

warn() {
    echo "$1" >&2
}

die() {
    warn "fatal: $1"
    exit 3
}

usage() {
    warn "usage: $0 [options] COPR_PROJECT"
    warn ""
    warn "Options:"
    warn ""
    warn "  -b BRN  build from branch BRN (default: last tag)"
    warn "  -n      dry mode, don't do anything (just show"
    warn "          what would be done)"
    warn "  -r REL  use REL as Release number in SPEC file"
    warn "  -v VER  use VER as Version number in SPEC file"
    warn "  -u URL  use URL as base (to get last tag and"
    warn "          compose Source0 in SPEC file)"
    warn ""
    warn "If -b is not used, build is launched from last tag available"
    warn "in the GitHub repo.  In that case, Release is '1' and Version"
    warn "is deduced from the tag by removing the initial 'v'."
    warn ""
    warn "If -b is used, the project repo is temporarily clonded, and"
    warn "both Version and Release are found by consulting git-describe"
    warn "on the specified branch."
    exit 2
}

last_version() {
    git ls-remote --tag "$UrlBase" \
      | grep '/tags/' \
      | cut -d/ -f3 \
      | sort -V \
      | tail -1 \
      | sed "s/^v//"
}

mkspec() {
    local self_version
    self_version="slop-build-copr $(git describe --tags)"
    sed -e "
        /^Version/ s|__SLOP_VERSION__|$Version|
        /^Release/ s|__SLOP_RELEASE__|$Release|
        /^Source0/ s|__SLOP_URLBASE__|$UrlBase|
        /^# spec file/ s|__SLOP_BUILDSCRIPT_VERSION__|$self_version|
    " <slop.spec.in
}

git_guess() {
    #
    # Print git-guessed $1
    #
    local what=$1   # what we want (ver|rel)
    local describe  # full git-describe output
    local xtra=     # extra part (-N-gHASH)
    local num=0     # num. of commits since tag (N)
    local sha=      # '.g'+sha1 of this commit (gHASH)
    describe=$(git describe --tags --always HEAD)
    case $describe in
        *-*)                        #     v1.2.3-21-g654cba
            tag=${describe%%-*}     # tag=v1.2.3
            xtra=${describe#$tag-}  # xtra=-21-g654cba
            num=${xtra%%-*}         # num=21
            sha=.${xtra#$num-}      # sha=.g654cba
            ;;
        *)
            tag=$describe
            ;;
    esac
    case $what in
        ver)    echo "${tag#v}"         ;;
        rel)    echo "$((num + 1))$sha" ;;
    esac
}

main() {
    local Version       # Version in SPEC file
    local Release       # Release in SPEC file
    local CoprProject   # COPR project
    local UrlBase       # GitHub URL base
    local Tmp           # our temp
    local Branch        # branch to use, if empty, tags are considered
    local DryRun=false  # do not do anything
    UrlBase=https://github.com/AloisMahdal/slop
    Tmp=$(mktemp -d)
    while true; do case $1 in
        -b) Branch=$2;      shift 2 || usage ;;
        -u) UrlBase=$2;     shift 2 || usage ;;
        -r) Release=$2;     shift 2 || usage ;;
        -v) Version=${2#v}; shift 2 || usage ;;
        -n) DryRun=true;    shift ;;
        -*) usage ;;
        *)  break ;;
    esac done
    CoprProject=$1
    test -n "$CoprProject" || usage
    which copr >/dev/null \
     || die "copr not found, try 'sudo install python-copr'"
    if test -n "$Branch"; then
        die "not implemented"
        test -n "$Version" || Version=$(git_guess ver)
        test -n "$Release" || Release=$(git_guess rel)
    else
        test -n "$Version" || Version=$(last_version)
        test -n "$Release" || Release=1
    fi
    mkspec >"$Tmp/slop.spec"
    $DryRun && {
        warn "dry mode active, we would build:"
        warn "    at $CoprProject"
        test -n "$Branch" && warn "    using branch $Branch"
        test -n "$Branch" || warn "    using last tag"
        warn "    from $UrlBase"
        warn "    yielding slop-$Version-$Release.*.rpm"
        warn ""
        warn "===== BEGIN slop.spec ====="
        cat "$Tmp/slop.spec"
        warn "===== END slop.spec ====="
        exit 1
    }
    copr build --nowait "$CoprProject" "$Tmp/slop.spec"
    rm -rf "$Tmp"
}

main "$@"