meal-order-manager/terraform/cloudfront.tf

resource "aws_cloudfront_origin_access_control" "form" {
  name                              = "${local.project}-oac"
  description                       = "OAC for the meal-order-manager form origin bucket"
  origin_access_control_origin_type = "s3"
  signing_behavior                  = "always"
  signing_protocol                  = "sigv4"
}

resource "aws_cloudfront_cache_policy" "menu_api" {
  name        = "${local.project}-menu-api"
  comment     = "Cache public menu responses for 60 seconds per request origin"
  default_ttl = 60
  max_ttl     = 60
  min_ttl     = 60

  parameters_in_cache_key_and_forwarded_to_origin {
    cookies_config {
      cookie_behavior = "none"
    }

    headers_config {
      header_behavior = "whitelist"
      headers {
        items = ["Origin"]
      }
    }

    query_strings_config {
      query_string_behavior = "none"
    }

    enable_accept_encoding_brotli = true
    enable_accept_encoding_gzip   = true
  }
}

resource "aws_cloudfront_origin_request_policy" "menu_api" {
  name    = "${local.project}-menu-api"
  comment = "Forward CORS preflight headers to the HTTP API"

  cookies_config {
    cookie_behavior = "none"
  }

  headers_config {
    header_behavior = "whitelist"
    headers {
      items = [
        "Access-Control-Request-Headers",
        "Access-Control-Request-Method",
      ]
    }
  }

  query_strings_config {
    query_string_behavior = "none"
  }
}

# Rewrite extensionless form paths to index.html on the S3 origin only.
# A distribution-wide 403 custom error page would also rewrite API 403s
# (non-admin, bad bearer) into form HTML.
resource "aws_cloudfront_function" "form_spa_rewrite" {
  name    = "${local.project}-form-spa-rewrite"
  runtime = "cloudfront-js-2.0"
  comment = "Rewrite extensionless form paths to /index.html"
  publish = true
  code    = <<-EOF
    function handler(event) {
      var request = event.request;
      var uri = request.uri;
      if (uri.lastIndexOf('.') <= uri.lastIndexOf('/')) {
        request.uri = '/index.html';
      }
      return request;
    }
  EOF
}

resource "aws_cloudfront_distribution" "form" {
  enabled             = true
  is_ipv6_enabled     = true
  http_version        = "http2and3"
  comment             = "meal-order-manager form hosting"
  default_root_object = "index.html"
  price_class         = "PriceClass_100"
  # Empty until DNS cutover: AWS rejects a second distribution claiming an
  # alias whose DNS still points at another CloudFront distribution (mgmt).
  aliases = var.attach_custom_domain ? [var.domain_name] : []

  # Shared org CloudFront WAF (audit M-17), resolved from Parameter Store.
  web_acl_id = data.aws_ssm_parameter.app_web_acl_arn.value

  origin {
    origin_id                = "S3FormOrigin"
    domain_name              = aws_s3_bucket.form.bucket_regional_domain_name
    origin_access_control_id = aws_cloudfront_origin_access_control.form.id
  }

  origin {
    origin_id   = "OrderApiOrigin"
    domain_name = aws_lb.api.dns_name

    custom_origin_config {
      http_port              = 80
      https_port             = 443
      origin_protocol_policy = "http-only"
      origin_ssl_protocols   = ["TLSv1.2"]
    }
  }

  ordered_cache_behavior {
    path_pattern             = "/api/menu/*"
    target_origin_id         = "OrderApiOrigin"
    viewer_protocol_policy   = "redirect-to-https"
    allowed_methods          = ["GET", "HEAD", "OPTIONS"]
    cached_methods           = ["GET", "HEAD"]
    compress                 = true
    cache_policy_id          = aws_cloudfront_cache_policy.menu_api.id
    origin_request_policy_id = aws_cloudfront_origin_request_policy.menu_api.id
  }

  # Do not use path `/api/*`. That would front HMAC publish routes.
  ordered_cache_behavior {
    path_pattern             = "/api/roster"
    target_origin_id         = "OrderApiOrigin"
    viewer_protocol_policy   = "redirect-to-https"
    allowed_methods          = ["GET", "HEAD", "OPTIONS"]
    cached_methods           = ["GET", "HEAD"]
    compress                 = true
    cache_policy_id          = local.api_cache_policy_id
    origin_request_policy_id = local.api_origin_request_policy_id
  }

  ordered_cache_behavior {
    path_pattern             = "/api/form-status/*"
    target_origin_id         = "OrderApiOrigin"
    viewer_protocol_policy   = "redirect-to-https"
    allowed_methods          = ["GET", "HEAD", "OPTIONS"]
    cached_methods           = ["GET", "HEAD"]
    compress                 = true
    cache_policy_id          = local.api_cache_policy_id
    origin_request_policy_id = local.api_origin_request_policy_id
  }

  ordered_cache_behavior {
    path_pattern             = "/api/orders/*"
    target_origin_id         = "OrderApiOrigin"
    viewer_protocol_policy   = "redirect-to-https"
    allowed_methods          = ["GET", "HEAD", "OPTIONS"]
    cached_methods           = ["GET", "HEAD"]
    compress                 = true
    cache_policy_id          = local.api_cache_policy_id
    origin_request_policy_id = local.api_origin_request_policy_id
  }

  ordered_cache_behavior {
    path_pattern             = "/api/submit-order"
    target_origin_id         = "OrderApiOrigin"
    viewer_protocol_policy   = "redirect-to-https"
    allowed_methods          = local.cloudfront_all_methods
    cached_methods           = ["GET", "HEAD"]
    compress                 = true
    cache_policy_id          = local.api_cache_policy_id
    origin_request_policy_id = local.api_origin_request_policy_id
  }

  ordered_cache_behavior {
    path_pattern             = "/api/admin/*"
    target_origin_id         = "OrderApiOrigin"
    viewer_protocol_policy   = "redirect-to-https"
    allowed_methods          = local.cloudfront_all_methods
    cached_methods           = ["GET", "HEAD"]
    compress                 = true
    cache_policy_id          = local.api_cache_policy_id
    origin_request_policy_id = local.api_origin_request_policy_id
  }

  default_cache_behavior {
    target_origin_id       = "S3FormOrigin"
    viewer_protocol_policy = "redirect-to-https"
    allowed_methods        = ["GET", "HEAD"]
    cached_methods         = ["GET", "HEAD"]
    compress               = true

    # AWS managed policy: CachingDisabled. The form HTML is republished weekly
    # and read through a signed API, so a stale edge copy is worse than an
    # origin fetch.
    cache_policy_id = local.api_cache_policy_id

    function_association {
      event_type   = "viewer-request"
      function_arn = aws_cloudfront_function.form_spa_rewrite.arn
    }
  }

  restrictions {
    geo_restriction {
      restriction_type = "none"
    }
  }

  viewer_certificate {
    cloudfront_default_certificate = !var.attach_custom_domain
    acm_certificate_arn            = var.attach_custom_domain ? data.aws_acm_certificate.orders[0].arn : null
    ssl_support_method             = var.attach_custom_domain ? "sni-only" : null
    minimum_protocol_version       = var.attach_custom_domain ? "TLSv1.2_2021" : null
  }

  lifecycle {
    # prevent_destroy cannot interpolate. Keep it on so a tagged apply cannot
    # destroy the live distribution; tear down a leftover dev distribution
    # from the AWS console.
    prevent_destroy = true
  }
}