locals {
    block_device_path = "/dev/sdh"
    user_data = <<EOF
#!/bin/bash
# Filesystem code is adapted from:
# https://github.com/GSA/devsecops-example/blob/03067f68ee2765f8477ae84235f7faa1d2f2cb70/terraform/files/attach-data-volume.sh

DEVICE=${local.block_device_path}
DEST=${var.persistent_volume_mount_path}
devpath=$(readlink -f $DEVICE)

if [[ $(file -s $devpath) != *ext4* && -b $devpath ]]; then
    # Filesystem has not been created. Create it!
    mkfs -t ext4 $devpath
fi

# add to fstab if not present
if ! egrep "^$devpath" /etc/fstab; then
  echo "$devpath $DEST ext4 defaults,nofail,noatime,nodiratime,barrier=0,data=writeback 0 2" | tee -a /etc/fstab > /dev/null
fi
mkdir -p $DEST
mount $DEST
chown ec2-user:ec2-user $DEST
chmod 0755 $DEST

# Filesystem code is over

# Now we install docker and docker-compose.
# Adapted from:
# https://gist.github.com/npearce/6f3c7826c7499587f00957fee62f8ee9
amazon-linux-extras install docker
systemctl start docker.service
usermod -a -G docker ec2-user
chkconfig docker on
yum install python3-pip
python3 -m pip install docker-compose

# Put the docker-compose.yml file at the root of our persistent volume
cat > $DEST/docker-compose.yml <<-TEMPLATE
${var.docker_compose_str}
TEMPLATE

# Write the systemd service that manages us bringing up the service
cat > /etc/systemd/system/my_custom_service.service <<-TEMPLATE
[Unit]
Description=${var.description}
After=${var.systemd_after_stage}

[Service]
Type=simple
User=${var.user}
ExecStart=/usr/local/bin/docker-compose -f $DEST/docker-compose.yml up
Restart=on-failure

[Install]
WantedBy=multi-user.target
TEMPLATE
# Start the service.
systemctl start my_custom_service
EOF
}

# This should pull the latest Amazon Linux 2, which comes with docker
# but not docker-compose...
data "aws_ami" "latest_amazon_linux" {
    most_recent = true
    owners = ["amazon"]
    filter {
        name = "name"
        values = ["amzn*"]
    }
}


resource "aws_ebs_volume" "persistent" {
    # TODO: Terraform tries to delete the volume when the AZ of the AWS instance changes.
    availability_zone = aws_instance.this.availability_zone
    size = var.persistent_volume_size_gb
}

resource "aws_volume_attachment" "persistent" {
    device_name = local.block_device_path
    volume_id = aws_ebs_volume.persistent.id
    instance_id = aws_instance.this.id
    skip_destroy = true
}

resource "aws_instance" "this" {
    ami = data.aws_ami.latest_amazon_linux.id
    instance_type = var.instance_type
    key_name = var.key_name
    associate_public_ip_address = var.associate_public_ip_address
    vpc_security_group_ids = var.vpc_security_group_ids
    subnet_id = var.subnet_id
    iam_instance_profile = var.iam_instance_profile
    user_data = local.user_data
    tags = merge (
        {
            Name = var.name
        },
        var.tags
    )
}