bootstrap

#!/bin/sh
set -euo pipefail

SCRIPT_DIR=$(cd $(dirname $0); pwd)
HANDLER_NAME=$(echo "$_HANDLER" | cut -d. -f2)
HANDLER_FILE=$(echo "$_HANDLER" | cut -d. -f1)

API_ROOT=http://${AWS_LAMBDA_RUNTIME_API}/2018-06-01/runtime/

# If this ENV variable is set then copy that directory as DENO_DIR (default = .deno_dir).
# Note: For permissions reasons we need the actual DENO_DIR to be somewhere in /tmp.
DENO_DIR=${DENO_DIR-.deno_dir}
if [[ -z "$DENO_DIR" ]]; then
  DENO_DIR=.deno_dir
fi

# Potentially this could be overwritten HOWEVER several permissions are required for bootstrap.
# FIXME should this simply be -A?
# FIXME can plugins work?? (If so, it should be documented.)
DENO_FLAGS="--allow-env --allow-net --allow-plugin --allow-read --allow-run --allow-write"
DENO_FETCH_FLAGS=""

# Once there is a convention for lock filename we could look for its existence.
# For now we require it to be passed as an env explicitly.
DENO_LOCK=${DENO_LOCK-}
if [[ ! -z "$DENO_LOCK" ]]; then
  DENO_FLAGS="$DENO_FLAGS --lock=$DENO_LOCK"
  DENO_FETCH_FLAGS="$DENO_FETCH_FLAGS --lock=$DENO_LOCK"
fi

DENO_CONFIG=${DENO_CONFIG-}
if [[ ! -z "$DENO_CONFIG" ]]; then
  DENO_FLAGS="$DENO_FLAGS --config=$DENO_CONFIG"
  DENO_FETCH_FLAGS="$DENO_FETCH_FLAGS --config=$DENO_CONFIG"
fi

DENO_IMPORTMAP=${DENO_IMPORTMAP-}
if [[ ! -z "$DENO_IMPORTMAP" ]]; then
  DENO_FLAGS="$DENO_FLAGS --importmap=$DENO_IMPORTMAP"
  DENO_FETCH_FLAGS="$DENO_FETCH_FLAGS --importmap=$DENO_IMPORTMAP"
fi

# whether to use ts, js, bundle.js, etc.
HANDLER_EXT=${HANDLER_EXT-'ts'}
HANDLER_FILE=${HANDLER_FILE}.${HANDLER_EXT}

# If we fail prior to the handler loop we post an init error.
function error {
  echo "error:" $1
  ERROR="{\"errorMessage\" : \"$1\", \"errorType\" : \"InitException\"}"
  curl -s -X POST "${API_ROOT}init/error" \
       -d "$ERROR" \
       --header "Lambda-Runtime-Function-Error-Type: Unhandled" \
       --output /tmp/init.out
  # expect it to be {"status":"OK"}
  grep -q OK /tmp/init.out \
   || echo "Unexpected bootstrap error when calling AWS_LAMBDA_RUNTIME_API /init/error:" $(cat /tmp/init.out)
  exit 1
}

# If the script fails we try and determine why.
function investigate {
  [ -f $SCRIPT_DIR/amz-deno ] \
   || error "missing amz-deno executable"

  $SCRIPT_DIR/amz-deno eval 'Deno.version.deno' \
   || error "bad amz-deno executable"

  [ -f $LAMBDA_TASK_ROOT/$HANDLER_FILE ] \
   || error "missing expected handler file '$HANDLER_FILE'"

  if [[ ! -z "$DENO_LOCK" ]]; then
    [ -f $DENO_LOCK ] \
     || error "missing lock file '$DENO_LOCK'"
    # This second check might be unecessary (in that it would be caught by the 'unable to compile')
    DENO_DIR=/tmp/deno_dir NO_COLOR=true $SCRIPT_DIR/amz-deno fetch $DENO_FETCH_FLAGS $LAMBDA_TASK_ROOT/$HANDLER_FILE &> /tmp/lock.out \
     || error "lock file error: $(cat /tmp/lock.out)"
  fi

  DENO_DIR=/tmp/deno_dir NO_COLOR=true $SCRIPT_DIR/amz-deno fetch $DENO_FETCH_FLAGS $LAMBDA_TASK_ROOT/$HANDLER_FILE 2> /dev/null \
   || error "unable to compile $HANDLER_FILE"

  echo "import { $HANDLER_NAME } from '$LAMBDA_TASK_ROOT/$HANDLER_FILE';" > /tmp/runtime-test.js
  DENO_DIR=/tmp/deno_dir NO_COLOR=true $SCRIPT_DIR/amz-deno fetch $DENO_IMPORTMAP /tmp/runtime-test.js 2> /dev/null \
   || error "$HANDLER_FILE must export a function named '$HANDLER_NAME'";

  # FIXME perhaps a bug in bootstrap? Should we always exit 1? Or not?
  error "deno exited"
}

# Note: This is a js file to avoid a runtime compilation step.
# Hopefully $HANDLER_FILE's compilation is cached in DENO_DIR.
echo "
import { $HANDLER_NAME } from '$LAMBDA_TASK_ROOT/$HANDLER_FILE';
const INVOCATION = '${API_ROOT}invocation/';
function tryParse(headers, headerName) {
  const json = headers.get(headerName);
  if (json) {
    try {
      return JSON.parse(json)
    } catch (e) {
      console.error(
        'Unable to parse header \'' + headerName + '\' value as JSON: ' + json)
    }
  }
}

while (true) {
  const next = await fetch(INVOCATION + 'next');
  const headers = next.headers;
  const reqId = headers.get('lambda-runtime-aws-request-id');
  const context = {
    functionName: '$AWS_LAMBDA_FUNCTION_NAME',
    functionVersion: '$AWS_LAMBDA_FUNCTION_VERSION',
    invokedFunctionArn: headers.get('lambda-runtime-invoked-function-arn'),
    memoryLimitInMB: '$AWS_LAMBDA_FUNCTION_MEMORY_SIZE',
    awsRequestId: headers.get('lambda-runtime-aws-request-id'),
    logGroupName: '$AWS_LAMBDA_LOG_GROUP_NAME',
    logStreamName: '$AWS_LAMBDA_LOG_STREAM_NAME',
    identity: tryParse(headers, 'lambda-runtime-cognito-identity'),
    clientContext: tryParse(headers, 'lambda-runtime-client-context'),
    getRemainingTimeInMillis: function() {
      return Number(headers.get('lambda-runtime-deadline-ms')) - Date.now();
    },
    // FIXME: we add these for type compatibility with Definitely Typed.
    callbackWaitsForEmptyEventLoop: undefined,
    done: undefined,
    fail: undefined,
    succeed: undefined
  }
  let res;
  try {
    const event = await next.json();
    const body = await $HANDLER_NAME(event, context);
    res = await fetch(INVOCATION + reqId + '/response', {
      method: 'POST',
      body: JSON.stringify(body)
    });
  } catch(e) {
    console.error(e);
    // If it's an Error we can pull these out cleanly...
    // BUT it's javascript so it could be anything!
    // If there's a better way, very happy to take suggestions.
    let name, message;
    try {
      name = e.name || 'Error'
    } catch (_) {
      name = 'Error'
    }
    try {
      message = e.message || e
    } catch (_) {
      message = e
    }
    if (typeof(name) !== 'string') {
      name = JSON.stringify(name)
    }
    if (typeof(message) !== 'string') {
      const s = JSON.stringify(message)
      message = s === undefined ? '' + message : s
    }
    res = await fetch(INVOCATION + reqId + '/error', {
      method: 'POST',
      body: JSON.stringify({
        errorMessage: message,
        errorType: name
      })
    });
  }
  await res.blob();
}
" > /tmp/runtime.js

# We copy DENO_DIR into a writable directory (/tmp/deno_dir)
# and expand DENO_DIR/LAMBDA_TASK_ROOT to match the new location ($LAMBDA_TASK_ROOT).

mkdir -p /tmp/deno_dir/gen/file$LAMBDA_TASK_ROOT
# We cp first from the deno-lambda-layer.
cp -R /opt/.deno_dir/gen/. /tmp/deno_dir/gen &> /dev/null \
 && cp -R /opt/.deno_dir/deps/. /tmp/deno_dir/deps &> /dev/null \
 && cp -R /opt/.deno_dir/LAMBDA_TASK_ROOT/. /tmp/deno_dir/gen/file$LAMBDA_TASK_ROOT &> /dev/null \
 || true
# Then we overwrite with from the DENO_DIR in the function code.
cp -R $LAMBDA_TASK_ROOT/$DENO_DIR/gen/. /tmp/deno_dir/gen &> /dev/null \
 && cp -R $LAMBDA_TASK_ROOT/$DENO_DIR/deps/. /tmp/deno_dir/deps &> /dev/null \
 && cp -R $LAMBDA_TASK_ROOT/$DENO_DIR/gen/. /tmp/deno_dir/gen &> /dev/null \
 && cp -R $LAMBDA_TASK_ROOT/$DENO_DIR/LAMBDA_TASK_ROOT/. /tmp/deno_dir/gen/file$LAMBDA_TASK_ROOT &> /dev/null \
 || echo "warn: unable to import '$DENO_DIR/' as DENO_DIR"

# FIXME remove DENO_FLAGS=DENO_FLAGS environment variable setting (used in testing only).
DENO_DIR=/tmp/deno_dir DENO_FLAGS=$DENO_FLAGS NO_COLOR=true $SCRIPT_DIR/amz-deno run $DENO_FLAGS /tmp/runtime.js \
 || investigate;

# For debugging purposes of the bootstrap script itself it's useful to change the extension to /tmp/runtime.ts
# and run this code instead to get more verbose and type errors during testing.
# Note: on production you will see the verbose error message anyway in cloudwatch logs.
# DENO_DIR=/tmp/deno_dir DENO_FLAGS=$DENO_FLAGS NO_COLOR=true $SCRIPT_DIR/amz-deno run $DENO_FLAGS /tmp/runtime.ts &> /tmp/fail.out \
#  || error "error: $(cat /tmp/fail.out)"