#!/bin/sh

# git-pk3-import: Import a PK3 into a branch of a bare Git repo.

set -x

# Helpers

die()
{
    echo "$(basename "$0"): error: $*" >&2
    exit 1
}

usage()
{
    cat <<EOF
Usage:

  # mandatory
  export GIT_DIR=/path/to/xonotic-maps.pk3dir.git # absolute path
  export GIT_WORK_TREE=/tmp/worktree # pk3 is extracted here
  # optional
  export GIT_AUTHOR_NAME="Some Guy"
  export GIT_AUTHOR_EMAIL="someguy@example.com"

  $(basename $0) nick branch map.pk3 [changes.txt]

EOF
}

# Check usage

[ $# -ge 3 -a $# -le 4 ] || {
    usage
    die "wrong number of arguments"
}

[ -z "$GIT_DIR" ] && {
    usage
    die "GIT_DIR not set"
}

[ -z "$GIT_WORK_TREE" ] && {
    usage
    die "GIT_WORK_TREE not set"
}

[ -z "$(ls -A "$GIT_WORK_TREE")" ] ||
die "GIT_WORK_TREE is not empty"

nick="$1"
branch=$(git check-ref-format --print "$nick/$2") ||
die "malformed branch name '$nick/$2'"
pk3path="$3"
pk3name="$(basename "$pk3path")"
changes="$4"

# Set up commit info

[ -z "$GIT_AUTHOR_NAME" ] && export GIT_AUTHOR_NAME="$nick"
[ -z "$GIT_AUTHOR_EMAIL" ] && export GIT_AUTHOR_EMAIL="${nick}@example.com"

message()
{
    echo -e "Import $pk3name\n" | cat - "$changes" 2> /dev/null
}

# Clean up on exit

cleanup_index=
cleanup_worktree=

cleanup()
{
    [ "$cleanup_index" ] && rm -f "$GIT_INDEX_FILE"
    [ "$cleanup_worktree" ] && find "$GIT_WORK_TREE" -mindepth 1 -delete
}

trap cleanup EXIT

# Set up index file, makes testing easier
[ -z "$GIT_INDEX_FILE" ] && {
    export GIT_INDEX_FILE="$GIT_DIR/pk3-import-index"
    cleanup_index=t
}

# Extract the PK3 (the -n suppresses prompting in an edge case)
unzip -n -qq "$pk3path" -d "$GIT_WORK_TREE" ||
die "couldn't extract PK3 contents"
cleanup_worktree=t

# Note the refs and the common ancestor
master=refs/heads/master
ref=refs/heads/$branch
base=$(git merge-base $master $ref 2> /dev/null) ||
base=$master

# Figure out the parent commit
parent=\
$(git rev-parse --verify -q $ref || git rev-parse --verify -q $base) ||
die "couldn't determine parent commit"

# Read the tree at base into index
git read-tree $base ||
die "couldn't initialize index"

# Reject any modified files, the mapper should create a branch instead
[ -z "$(git diff-files --diff-filter=M)" ] ||
die "found changes to files in master"

# Force reading of .gitignore files from cache, not the work tree
git ls-files --cached -z |
grep -z '\.gitignore$' |
git update-index --skip-worktree -z --stdin ||
die "couldn't set up exclude patterns from index"

# Add untracked files; to filter out generated files such as BSP, add
# them to .gitignore and push, --exclude-standard (and the above hack)
# takes care of the rest
git ls-files --exclude-standard -o -z |
git update-index --add -z --stdin ||
die "couldn't add files to index"

# Check if the index contains changes against parent
git diff-index --cached --quiet $parent &&
die "found no changes to commit"

# Commit the index and point the ref to the new commit
tree=$(git write-tree) &&
commit=$(message | git commit-tree $tree -p $parent) &&
git update-ref -m "pk3-import: $pk3name" $ref $commit ||
die "couldn't commit changes"