#!/usr/bin/env bash
set -euo pipefail

# build-plan.sh
# Calculates whether to build from scratch, skip tests, or retag an existing image.
#
# Inputs (via env or arguments):
#   REF: Git reference (e.g. refs/heads/dev, refs/heads/main, refs/tags/v0.10.0)
#   COMMIT: Commit SHA or HEAD (defaults to HEAD)
#   IMAGE: Docker image repository name (e.g. git.dsit.me/sandrodach/mindsift)
#   PKG_VERSION: Package version from package.json (optional, auto-detected)
#   CHECK_IMAGE_CMD: Command to check image existence in registry (default: "docker manifest inspect")

REF="${REF:-${1:-}}"
COMMIT="${COMMIT:-${2:-HEAD}}"
IMAGE="${IMAGE:-${3:-}}"
PKG_VERSION="${PKG_VERSION:-${4:-}}"
CHECK_CMD="${CHECK_IMAGE_CMD:-docker manifest inspect}"

if [ -z "${REF}" ]; then
  REF="$(git symbolic-ref -q HEAD 2>/dev/null || git describe --tags --exact-match 2>/dev/null || echo "refs/heads/dev")"
fi

if [ -z "${PKG_VERSION}" ] && [ -f "frontend/package.json" ]; then
  PKG_VERSION="$(sed -nE 's/^  "version": "([^"]+)".*/\1/p' frontend/package.json | head -n1)"
fi

SHORT_SHA="$(git rev-parse --short=8 "${COMMIT}^{commit}" 2>/dev/null || echo "unknown")"
SHORT_TREE="$(git rev-parse --short=12 "${COMMIT}^{tree}" 2>/dev/null || echo "unknown")"

image_exists() {
  local target="$1"
  ${CHECK_CMD} "${target}" >/dev/null 2>&1
}

ACTION="build"
SKIP_TESTS="0"
APP_VERSION=""
TAGS=""
SOURCE_IMAGE=""
REASON=""

case "${REF}" in
  refs/heads/dev|dev)
    ACTION="build"
    SKIP_TESTS="0"
    APP_VERSION=""
    TAGS="dev tree-${SHORT_TREE}"
    REASON="Dev branch push: running full frontend and backend tests, tagging :dev and :tree-${SHORT_TREE}"
    ;;

  refs/heads/main|main)
    ACTION="build"
    APP_VERSION="v${PKG_VERSION}"
    TAGS="latest sha-${SHORT_SHA} tree-${SHORT_TREE}"

    # Check if this exact tree was already successfully tested on dev
    if [ -n "${IMAGE}" ] && image_exists "${IMAGE}:tree-${SHORT_TREE}"; then
      SKIP_TESTS="1"
      REASON="Main branch merge/push: tree :tree-${SHORT_TREE} was already tested on dev. Skipping tests (SKIP_TESTS=1)."
    else
      SKIP_TESTS="0"
      REASON="Main branch merge/push: tree :tree-${SHORT_TREE} not found in registry. Running full tests (SKIP_TESTS=0)."
    fi
    ;;

  refs/tags/v*|v*)
    TAG_NAME="${REF#refs/tags/}"
    # If pre-release (contains hyphen like v1.0.0-rc.1), do not tag :stable
    if [[ "${TAG_NAME}" == *-* ]]; then
      TARGET_TAGS="${TAG_NAME}"
    else
      TARGET_TAGS="${TAG_NAME} stable"
    fi

    # Check if a main image was already built for this exact commit
    if [ -n "${IMAGE}" ] && image_exists "${IMAGE}:sha-${SHORT_SHA}"; then
      ACTION="retag"
      SOURCE_IMAGE="${IMAGE}:sha-${SHORT_SHA}"
      SKIP_TESTS="1"
      TAGS="${TARGET_TAGS}"
      REASON="Release tag ${TAG_NAME} points to commit with existing image (${IMAGE}:sha-${SHORT_SHA}). Retagging without rebuild."
    else
      ACTION="build"
      APP_VERSION="${TAG_NAME}"
      TAGS="${TARGET_TAGS}"
      if [ -n "${IMAGE}" ] && image_exists "${IMAGE}:tree-${SHORT_TREE}"; then
        SKIP_TESTS="1"
        REASON="Release tag ${TAG_NAME}: :sha-${SHORT_SHA} not found, but tree was tested on dev. Building with SKIP_TESTS=1."
      else
        SKIP_TESTS="0"
        REASON="Release tag ${TAG_NAME}: :sha-${SHORT_SHA} not found and tree not verified. Building with full tests (SKIP_TESTS=0)."
      fi
    fi
    ;;

  *)
    REF_SLUG="$(echo "${REF#refs/heads/}" | sed 's#/#-#g' | tr '[:upper:]' '[:lower:]')"
    ACTION="build"
    SKIP_TESTS="0"
    APP_VERSION=""
    TAGS="${REF_SLUG}"
    REASON="Feature/other branch (${REF}): building with full tests"
    ;;
esac

# Output to stdout
echo "ACTION=${ACTION}"
echo "SKIP_TESTS=${SKIP_TESTS}"
echo "APP_VERSION=${APP_VERSION}"
echo "TAGS=${TAGS}"
echo "SOURCE_IMAGE=${SOURCE_IMAGE}"
echo "SHORT_SHA=${SHORT_SHA}"
echo "SHORT_TREE=${SHORT_TREE}"
echo "REASON=${REASON}"

# Output to GITHUB_OUTPUT if present
if [ -n "${GITHUB_OUTPUT:-}" ] && [ -w "${GITHUB_OUTPUT}" ]; then
  echo "action=${ACTION}" >> "${GITHUB_OUTPUT}"
  echo "skip_tests=${SKIP_TESTS}" >> "${GITHUB_OUTPUT}"
  echo "app_version=${APP_VERSION}" >> "${GITHUB_OUTPUT}"
  echo "tags=${TAGS}" >> "${GITHUB_OUTPUT}"
  echo "source_image=${SOURCE_IMAGE}" >> "${GITHUB_OUTPUT}"
  echo "short_sha=${SHORT_SHA}" >> "${GITHUB_OUTPUT}"
  echo "short_tree=${SHORT_TREE}" >> "${GITHUB_OUTPUT}"
  echo "reason=${REASON}" >> "${GITHUB_OUTPUT}"
fi