#!/usr/bin/env bash

set -euo pipefail

readonly PACKAGE_NAME="mk"
readonly REMOTE_NAME="origin"
readonly CHANGELOG_FILE="CHANGELOG.md"

usage() {
  cat <<'EOF'
Usage: scripts/release.sh [options] [<version>]

Bump the package version, verify the crate, publish it to crates.io,
create a git tag, and push the release commit and tag to origin.

Options:
  --major         Increment the major version and reset minor/patch to zero.
  --minor         Increment the minor version and reset patch to zero.
  --patch         Increment the patch version.
  --skip-publish  Skip `cargo publish` and only prepare/tag/push the release.
  --skip-push     Skip pushing the release commit and tag to origin.
  -h, --help      Show this help message.

Examples:
  scripts/release.sh 0.4.3
  scripts/release.sh --patch
  scripts/release.sh --minor --skip-push
  scripts/release.sh --skip-publish --skip-push 0.4.3
EOF
}

die() {
  printf 'error: %s\n' "$*" >&2
  exit 1
}

need_cmd() {
  command -v "$1" >/dev/null 2>&1 || die "required command not found: $1"
}

append_section_entry() {
  local section_name="$1"
  local entry="$2"
  printf -v "$section_name" '%s- %s\n' "${!section_name}" "$entry"
}

ensure_clean_worktree() {
  git diff --quiet --exit-code || die "working tree has unstaged changes"
  git diff --cached --quiet --exit-code || die "index has staged but uncommitted changes"
}

current_version() {
  awk '
    BEGIN { in_package = 0 }
    /^\[package\]$/ { in_package = 1; next }
    /^\[/ && $0 != "[package]" && in_package { in_package = 0 }
    in_package && /^version = "/ {
      gsub(/^version = "/, "", $0)
      gsub(/"$/, "", $0)
      print
      exit
    }
  ' Cargo.toml
}

increment_version() {
  local current="$1"
  local bump_kind="$2"
  local major minor patch

  IFS='.' read -r major minor patch <<<"$current"

  case "$bump_kind" in
    major)
      ((major += 1))
      minor=0
      patch=0
      ;;
    minor)
      ((minor += 1))
      patch=0
      ;;
    patch)
      ((patch += 1))
      ;;
    *)
      die "unsupported bump kind: $bump_kind"
      ;;
  esac

  printf '%s.%s.%s\n' "$major" "$minor" "$patch"
}

update_manifest_version() {
  local version="$1"
  local tmp
  tmp="$(mktemp)"

  awk -v version="$version" '
    BEGIN { in_package = 0; replaced = 0 }
    /^\[package\]$/ { in_package = 1 }
    /^\[/ && $0 != "[package]" && in_package { in_package = 0 }
    in_package && /^version = "/ && !replaced {
      print "version = \"" version "\""
      replaced = 1
      next
    }
    { print }
    END {
      if (!replaced) {
        exit 1
      }
    }
  ' Cargo.toml >"$tmp" || {
    rm -f "$tmp"
    die "failed to update Cargo.toml version"
  }

  mv "$tmp" Cargo.toml
}

update_lockfile_version() {
  local version="$1"
  local tmp
  tmp="$(mktemp)"

  awk -v version="$version" -v package_name="$PACKAGE_NAME" '
    BEGIN { in_package = 0; target = 0; replaced = 0 }
    /^\[\[package\]\]$/ {
      in_package = 1
      target = 0
    }
    in_package && $0 == "name = \"" package_name "\"" {
      target = 1
    }
    target && /^version = "/ && !replaced {
      print "version = \"" version "\""
      replaced = 1
      target = 0
      next
    }
    { print }
    END {
      if (!replaced) {
        exit 1
      }
    }
  ' Cargo.lock >"$tmp" || {
    rm -f "$tmp"
    die "failed to update Cargo.lock version"
  }

  mv "$tmp" Cargo.lock
}

previous_release_tag() {
  git describe --tags --abbrev=0 --match '[0-9]*.[0-9]*.[0-9]*' 2>/dev/null || true
}

render_changelog_group() {
  local title="$1"
  local content="$2"

  [[ -n "$content" ]] || return 0

  printf '### %s\n\n' "$title"
  printf '%s\n' "$content"
}

update_changelog() {
  local version="$1"
  local release_date="$2"
  local previous_tag="$3"
  local log_range
  local features=""
  local fixes=""
  local docs=""
  local tests=""
  local ci=""
  local maintenance=""
  local other=""
  local entry_count=0
  local conventional_commit_regex='^([[:alnum:]_-]+)(\([^)]+\))?(!)?:[[:space:]]*(.+)$'

  if [[ -n "$previous_tag" ]]; then
    log_range="${previous_tag}..HEAD"
  else
    log_range="HEAD"
  fi

  while IFS=$'\t' read -r commit_sha subject; do
    local short_sha category message
    [[ -n "$commit_sha" ]] || continue

    short_sha="$(git rev-parse --short "$commit_sha")"
    category="other"
    message="$subject"

    if [[ "$subject" =~ $conventional_commit_regex ]]; then
      local commit_type
      commit_type="${BASH_REMATCH[1]}"
      message="${BASH_REMATCH[4]}"

      case "$commit_type" in
        feat)
          category="features"
          ;;
        fix)
          category="fixes"
          ;;
        docs)
          category="docs"
          ;;
        test)
          category="tests"
          ;;
        ci)
          category="ci"
          ;;
        build|style|refactor|perf|chore)
          category="maintenance"
          ;;
      esac
    fi

    case "$category" in
      features)
        append_section_entry features "${message} (\`${short_sha}\`)"
        ;;
      fixes)
        append_section_entry fixes "${message} (\`${short_sha}\`)"
        ;;
      docs)
        append_section_entry docs "${message} (\`${short_sha}\`)"
        ;;
      tests)
        append_section_entry tests "${message} (\`${short_sha}\`)"
        ;;
      ci)
        append_section_entry ci "${message} (\`${short_sha}\`)"
        ;;
      maintenance)
        append_section_entry maintenance "${message} (\`${short_sha}\`)"
        ;;
      *)
        append_section_entry other "${message} (\`${short_sha}\`)"
        ;;
    esac

    ((entry_count += 1))
  done < <(git log --reverse --format='%H%x09%s' "$log_range")

  ((entry_count > 0)) || die "no commits found for changelog range: ${log_range}"

  if [[ -f "$CHANGELOG_FILE" ]] && grep -Eq "^## ${version//./\\.}([[:space:]]|$)" "$CHANGELOG_FILE"; then
    die "$CHANGELOG_FILE already contains an entry for version $version"
  fi

  local tmp existing_content
  tmp="$(mktemp)"
  existing_content=""

  if [[ -f "$CHANGELOG_FILE" ]]; then
    existing_content="$(
      awk '
        NR == 1 && $0 == "# Changelog" {
          header = 1
          next
        }
        header && !body_started && $0 == "" { next }
        {
          body_started = 1
          print
        }
      ' "$CHANGELOG_FILE"
    )"
  fi

  {
    printf '# Changelog\n\n'
    printf '## %s - %s\n\n' "$version" "$release_date"
    render_changelog_group "Features" "$features"
    render_changelog_group "Fixes" "$fixes"
    render_changelog_group "Documentation" "$docs"
    render_changelog_group "Tests" "$tests"
    render_changelog_group "CI" "$ci"
    render_changelog_group "Maintenance" "$maintenance"
    render_changelog_group "Other Changes" "$other"

    if [[ -n "$existing_content" ]]; then
      printf '%s\n' "$existing_content"
    fi
  } >"$tmp"

  mv "$tmp" "$CHANGELOG_FILE"
}

main() {
  local run_publish=1
  local run_push=1
  local version=""
  local bump_kind=""
  local previous_tag=""
  local release_date=""

  while (($# > 0)); do
    case "$1" in
      --major|--minor|--patch)
        [[ -z "$bump_kind" ]] || die "only one of --major, --minor, or --patch may be used"
        bump_kind="${1#--}"
        shift
        ;;
      --skip-publish)
        run_publish=0
        shift
        ;;
      --skip-push)
        run_push=0
        shift
        ;;
      -h|--help)
        usage
        exit 0
        ;;
      -*)
        die "unknown option: $1"
        ;;
      *)
        if [[ -n "$version" ]]; then
          die "version may only be provided once"
        fi
        version="$1"
        shift
        ;;
    esac
  done

  if [[ -z "$version" && -z "$bump_kind" ]]; then
    usage
    exit 1
  fi

  [[ -z "$version" || -z "$bump_kind" ]] || die "pass either an explicit version or one bump flag"

  need_cmd awk
  need_cmd cargo
  need_cmd date
  need_cmd git
  need_cmd mktemp

  local repo_root
  repo_root="$(git rev-parse --show-toplevel 2>/dev/null)" || die "must be run inside a git repository"
  cd "$repo_root"

  ensure_clean_worktree

  git remote get-url "$REMOTE_NAME" >/dev/null 2>&1 || die "git remote '$REMOTE_NAME' is not configured"

  local old_version
  old_version="$(current_version)"
  [[ -n "$old_version" ]] || die "failed to read current package version"
  [[ "$old_version" =~ ^[0-9]+\.[0-9]+\.[0-9]+$ ]] || die "current version must match x.y.z"

  if [[ -n "$bump_kind" ]]; then
    version="$(increment_version "$old_version" "$bump_kind")"
  fi

  [[ "$version" =~ ^[0-9]+\.[0-9]+\.[0-9]+$ ]] || die "version must match x.y.z"
  [[ "$old_version" != "$version" ]] || die "version is already $version"

  git rev-parse --verify "refs/tags/$version" >/dev/null 2>&1 && die "tag '$version' already exists locally"
  git ls-remote --exit-code --tags "$REMOTE_NAME" "refs/tags/$version" >/dev/null 2>&1 && die "tag '$version' already exists on '$REMOTE_NAME'"

  previous_tag="$(previous_release_tag)"
  release_date="$(date +%Y-%m-%d)"

  update_manifest_version "$version"
  update_lockfile_version "$version"
  update_changelog "$version" "$release_date" "$previous_tag"

  cargo fmt
  cargo test
  cargo clippy --all-targets --all-features -- -D warnings

  git add Cargo.toml Cargo.lock "$CHANGELOG_FILE"
  git commit -m "release: $version"

  cargo publish --dry-run

  if ((run_publish)); then
    cargo publish
  fi

  git tag -a "$version" -m "release: $version"

  if ((run_push)); then
    git push "$REMOTE_NAME" HEAD
    git push "$REMOTE_NAME" "$version"
  fi

  printf 'Released %s -> %s\n' "$old_version" "$version"
}

main "$@"