data "aws_availability_zones" "available" {
  count = local.manage_vpc ? 1 : 0
  state = "available"
}

data "aws_vpc" "existing" {
  count = var.existing_vpc_id == "" ? 0 : 1
  id    = var.existing_vpc_id
}

data "aws_subnet" "existing_public" {
  for_each = toset(var.existing_public_subnet_ids)
  id       = each.value
}

data "aws_subnet" "existing_private" {
  for_each = toset(var.existing_private_subnet_ids)
  id       = each.value
}

data "aws_ec2_managed_prefix_list" "cloudfront_origin" {
  name = "com.amazonaws.global.cloudfront.origin-facing"
}

resource "aws_vpc" "this" {
  count = local.manage_vpc ? 1 : 0

  cidr_block           = local.vpc_cidr
  enable_dns_support   = true
  enable_dns_hostnames = true

  tags = {
    Name = "${local.project}-vpc"
  }
}

resource "aws_internet_gateway" "this" {
  count = local.manage_vpc ? 1 : 0

  vpc_id = aws_vpc.this[0].id

  tags = {
    Name = "${local.project}-igw"
  }
}

resource "aws_subnet" "public" {
  count = local.manage_vpc ? length(local.public_subnet_cidrs) : 0

  vpc_id                  = aws_vpc.this[0].id
  cidr_block              = local.public_subnet_cidrs[count.index]
  availability_zone       = data.aws_availability_zones.available[0].names[count.index]
  map_public_ip_on_launch = true

  tags = {
    Name = "${local.project}-public-${count.index}"
  }
}

resource "aws_subnet" "private" {
  count = local.manage_vpc ? length(local.private_subnet_cidrs) : 0

  vpc_id            = aws_vpc.this[0].id
  cidr_block        = local.private_subnet_cidrs[count.index]
  availability_zone = data.aws_availability_zones.available[0].names[count.index]

  tags = {
    Name = "${local.project}-private-${count.index}"
  }
}

resource "aws_route_table" "public" {
  count = local.manage_vpc ? 1 : 0

  vpc_id = aws_vpc.this[0].id

  tags = {
    Name = "${local.project}-public"
  }
}

resource "aws_route" "public_default" {
  count = local.manage_vpc ? 1 : 0

  route_table_id         = aws_route_table.public[0].id
  destination_cidr_block = "0.0.0.0/0"
  gateway_id             = aws_internet_gateway.this[0].id
}

resource "aws_route_table_association" "public" {
  count = local.manage_vpc ? length(local.public_subnet_cidrs) : 0

  subnet_id      = aws_subnet.public[count.index].id
  route_table_id = aws_route_table.public[0].id
}

locals {
  vpc_id             = local.manage_vpc ? aws_vpc.this[0].id : try(data.aws_vpc.existing[0].id, var.existing_vpc_id)
  public_subnet_ids  = local.manage_vpc ? aws_subnet.public[*].id : var.existing_public_subnet_ids
  private_subnet_ids = local.manage_vpc ? aws_subnet.private[*].id : var.existing_private_subnet_ids
}