#!/usr/bin/env bash

set -Eeuo pipefail

usage() {
  cat <<EOF
Usage: $(basename "${BASH_SOURCE[0]}") COMMIT_HASH

Transforms the given COMMIT_HASH into a blog post.

Available options:

-h, --help      Print this help and exit
EOF
  exit
}


msg() {
  echo >&2 -e "${1-}"
}

die() {
  local msg=$1
  local code=${2-1} # default exit status 1
  msg "$msg"
  exit "$code"
}

parse_params() {
  while :; do
    case "${1-}" in
    -h | --help) usage ;;
    -?*) die "Unknown option: $1" ;;
    *) break ;;
    esac
    shift
  done

  args=("$@")
  if [[ ${#args[@]} -eq 0 ]]; then
    commit=$(latest-commit)
  else
    commit=$(git show "${args[0]}" --no-patch --format=%H)
  fi

  return 0
}

latest-commit() {
  git show --no-patch --format=%H
}

blog-commit() {
  commit=$1
  git show "$commit" --format="Draft: yes%nDate: %ai%n%n# %s - $(repo)%n%n%b%n%x60%x60%x60diff%nZZZZZ" --patch | rg -v "No newline at end of file" | rg -v -U "ZZZZZ\n\n"
  echo '```'
  echo
  commit-link "$1"
}

commit-link() {
  commit=$1
  echo "[$commit on $(repo)]($(repo-link)/commit/$commit)"
}

blog-file() {
  commit=$1
  git show "$commit" --no-patch --format="%f.md"
}

repo() {
  git remote -v | rg fetch | awk -F: '{print $2}' | awk -F. '{print $1}'
}

repo-link() {
  git remote -v | rg fetch | awk -F: '{print $2}' | awk -F. '{print "https://github.com/" $1}'
}

main() {
  year=$(date +%Y)
  parse_params "$@"
  contents=$(blog-commit "$commit")
  filename=$(blog-file "$commit" | tr "[:upper:]" "[:lower:]")
  mkdir -p "$BLOG_DIR$year"
  msg "Writing to $BLOG_DIR$year/$filename"
  echo "$contents" > "$BLOG_DIR$year/$filename"
}

main "$@"