#!/bin/bash
#############################################################################
# PURPOSE: Build and optionally deploy a Lambda layer for user-specified Python libraries.
#
# PREREQUISITES:
#   docker, aws cli
#
# USAGE:
#   Save the python libraries you want in the lambda layer in
#   requirements.txt, then run like this:
#
#   ./build-lambda-layer.sh <path to requirements.txt> [s3 bucket path] [aws region]
#
# EXAMPLE:
#   To build but not publish the Lambda layer zip files:
#       ./build-lambda-layer.sh ./requirements.txt
#   To build the zip files and publish Lambda layers:
#       ./build-lambda-layer.sh ./requirements.txt s3://my_bucket/lambda_layers/ us-west-2
#
#############################################################################


# Check to see if input has been provided:
if [ -z "$1" ] || ([ -n "$2" ] && [ -z "$3" ]); then
    echo "Please provide a fully qualified s3 bucket for the lambda layer code to reside and the region of the deploy."
    echo "USAGE: ./build-lambda-layer.sh <requirements.txt> [s3 bucket path] [aws region]"
    echo "To build but not publish the Lambda layer zip files:"
    echo -e "\t./build-lambda-layer.sh ./requirements.txt"
    echo "To build the zip files and publish Lambda layers:"
    echo -e "\t./build-lambda-layer.sh ./requirements.txt s3://my_bucket/lambda_layers/ us-west-2"
    exit 1
fi

REQUIREMENTS_FILE="$1"
S3_BUCKET=$(echo "$2" | cut -f 3 -d "/")
S3_FQDN="$2"

# Check to see if requirements.txt file exists

if [ ! -f "$REQUIREMENTS_FILE" ]; then
    echo "$REQUIREMENTS_FILE does not exist"
    exit 1
fi

# Check to see if AWS CLI and Docker are installed
docker --version
if [ $? -ne 0 ]; then
  echo "ERROR: install Docker before running this script"
  exit 1
else
  docker ps > /dev/null
  if [ $? -ne 0 ]; then
      echo "ERROR: start Docker before running this script"
      exit 1
  fi
fi

echo "------------------------------------------------------------------------------"
echo "Building Lambda Layer zip file"
echo "------------------------------------------------------------------------------"
rm -rf ./lambda_layer-python-3.7/
rm -rf ./lambda_layer-python-3.8/
rm -rf ./lambda_layer-python-3.9/
rm -f ./lambda_layer-python3.7.zip
rm -f ./lambda_layer-python3.8.zip
rm -f ./lambda_layer-python3.9.zip
docker build --tag=lambda_layer_factory:latest . 2>&1 > /dev/null
if [ $? -eq 0 ]; then
  docker run --rm -v "$PWD":/packages lambda_layer_factory
fi
if [[ ! -f ./lambda_layer-python3.7.zip ]] || [[ ! -f ./lambda_layer-python3.8.zip ]] || [[ ! -f ./lambda_layer-python3.9.zip ]]; then
    echo "ERROR: Failed to build lambda layer zip file."
    exit 1
fi
echo "------------------------------------------------------------------------------"
echo "Verifying the Lambda layer meets AWS size limits"
echo "------------------------------------------------------------------------------"
# See https://docs.aws.amazon.com/lambda/latest/dg/limits.html
unzip -q -d lambda_layer-python-3.7 ./lambda_layer-python3.7.zip
unzip -q -d lambda_layer-python-3.8 ./lambda_layer-python3.8.zip
unzip -q -d lambda_layer-python-3.9 ./lambda_layer-python3.9.zip
ZIPPED_LIMIT=50
UNZIPPED_LIMIT=250
UNZIPPED_SIZE_37=$(du -sm ./lambda_layer-python-3.7/ | cut -f 1)
ZIPPED_SIZE_37=$(du -sm ./lambda_layer-python3.7.zip | cut -f 1)
UNZIPPED_SIZE_38=$(du -sm ./lambda_layer-python-3.8/ | cut -f 1)
ZIPPED_SIZE_38=$(du -sm ./lambda_layer-python3.8.zip | cut -f 1)
UNZIPPED_SIZE_39=$(du -sm ./lambda_layer-python-3.9/ | cut -f 1)
ZIPPED_SIZE_39=$(du -sm ./lambda_layer-python3.9.zip | cut -f 1)
rm -rf ./lambda_layer-python-3.7/
rm -rf ./lambda_layer-python-3.8/
rm -rf ./lambda_layer-python-3.9/
if (( $UNZIPPED_SIZE_37 > $UNZIPPED_LIMIT || $ZIPPED_SIZE_37 > $ZIPPED_LIMIT || $UNZIPPED_SIZE_38 > $UNZIPPED_LIMIT || $ZIPPED_SIZE_38 > $ZIPPED_LIMIT || $UNZIPPED_SIZE_39 > $UNZIPPED_LIMIT || $ZIPPED_SIZE_39 > $ZIPPED_LIMIT)); then
	echo "ERROR: Deployment package exceeds AWS Lambda layer size limits.";
	exit 1
fi
echo "Lambda layers have been saved to ./lambda_layer-python3.7.zip, ./lambda_layer-python3.8.zip, and ./lambda_layer-python3.9.zip."

if [ -n "$S3_FQDN" ]; then
    command -v aws > /dev/null
    if [ $? -ne 0 ]; then
        echo "ERROR: install the AWS CLI before running this script"
        exit 1
    fi
    ACCOUNT_ID=$(aws sts get-caller-identity --output text --query 'Account')
    echo "------------------------------------------------------------------------------"
    echo "Validating access to S3"
    echo "------------------------------------------------------------------------------"
    aws s3 mb "$S3_BUCKET" 2> /dev/null
    aws s3 ls "$S3_BUCKET" > /dev/null
    if [ $? -ne 0 ]; then
        echo "ERROR: Failed accessing $S3_FQDN"
    fi
    echo "------------------------------------------------------------------------------"
    echo "Publishing Lambda Layer to AWS account $ACCOUNT_ID"
    echo "------------------------------------------------------------------------------"
    LAMBDA_LAYERS_BUCKET=lambda-layers-$ACCOUNT_ID
    LAYER_NAME_37=lambda_layer-python37
    LAYER_NAME_38=lambda_layer-python38
    LAYER_NAME_39=lambda_layer-python39
    # create temp working dir for zip files
    aws s3 mb s3://"$LAMBDA_LAYERS_BUCKET" > /dev/null
    # Warn user if layer already exists
    aws lambda list-layer-versions --layer-name $LAYER_NAME_37 | grep "\"LayerVersions\": \["
    if [ $? -eq 0 ]; then
        echo "WARNING: AWS Layer with name $LAYER_NAME_37 already exists."
        read -r -p "Are you sure you want to overwrite $LAYER_NAME_37? [y/N] " response
        if [[ "$response" =~ ^([yY][eE][sS]|[yY])+$ ]]
        then
            aws s3 cp lambda_layer-python3.7.zip s3://"$LAMBDA_LAYERS_BUCKET"
            aws lambda publish-layer-version --layer-name $LAYER_NAME_37 --content S3Bucket="$LAMBDA_LAYERS_BUCKET",S3Key=lambda_layer-python3.7.zip --compatible-runtimes python3.7
            aws s3 rm s3://"$LAMBDA_LAYERS_BUCKET"/lambda_layer-python3.7.zip
            arn37=$(aws lambda list-layer-versions --layer-name $LAYER_NAME_37 --output text --query 'LayerVersions[0].LayerVersionArn')
        fi
    fi
    aws lambda list-layer-versions --layer-name $LAYER_NAME_38 | grep "\"LayerVersions\": \["
    if [ $? -eq 0 ]; then
        echo "WARNING: AWS Layer with name $LAYER_NAME_38 already exists."
        read -r -p "Are you sure you want to overwrite $LAYER_NAME_38? [y/N] " response
        if [[ "$response" =~ ^([yY][eE][sS]|[yY])+$ ]]
        then
            aws s3 cp lambda_layer-python3.8.zip s3://"$LAMBDA_LAYERS_BUCKET"
            aws lambda publish-layer-version --layer-name $LAYER_NAME_38 --content S3Bucket="$LAMBDA_LAYERS_BUCKET",S3Key=lambda_layer-python3.8.zip --compatible-runtimes python3.8
            aws s3 rm s3://"$LAMBDA_LAYERS_BUCKET"/lambda_layer-python3.8.zip
            arn38=$(aws lambda list-layer-versions --layer-name $LAYER_NAME_38 --output text --query 'LayerVersions[0].LayerVersionArn')
        fi
    fi
    aws lambda list-layer-versions --layer-name $LAYER_NAME_39 | grep "\"LayerVersions\": \["
    if [ $? -eq 0 ]; then
        echo "WARNING: AWS Layer with name $LAYER_NAME_39 already exists."
        read -r -p "Are you sure you want to overwrite $LAYER_NAME_39? [y/N] " response
        if [[ "$response" =~ ^([yY][eE][sS]|[yY])+$ ]]
        then
            aws s3 cp lambda_layer-python3.9.zip s3://"$LAMBDA_LAYERS_BUCKET"
            aws lambda publish-layer-version --layer-name $LAYER_NAME_39 --content S3Bucket="$LAMBDA_LAYERS_BUCKET",S3Key=lambda_layer-python3.9.zip --compatible-runtimes python3.9
            aws s3 rm s3://"$LAMBDA_LAYERS_BUCKET"/lambda_layer-python3.9.zip
            arn39=$(aws lambda list-layer-versions --layer-name $LAYER_NAME_39 --output text --query 'LayerVersions[0].LayerVersionArn')
        fi
    fi
    # remove temp working dir for zip files
    aws s3 rb s3://"$LAMBDA_LAYERS_BUCKET"/ > /dev/null
    echo "Lambda layers have been published. Use the following ARNs to attach them to Lambda functions:"
    echo "$arn37"
    echo "$arn38"
    echo "$arn39"
fi

echo "------------------------------------------------------------------------------"
echo "Done"
echo "------------------------------------------------------------------------------"