Add prysm.sh script (#5042)

* Add prysm.sh script

* Add dist to gitignore

Co-authored-by: prylabs-bulldozer[bot] <58059840+prylabs-bulldozer[bot]@users.noreply.github.com>

.gitignore

@@ -29,3 +29,6 @@ password.txt
 # go dependancy
 /go.mod
 /go.sum
+
+# Dist files
+dist

prysm.sh

@@ -0,0 +1,131 @@
+#!/bin/bash
+
+set -eu
+
+# Use this script to download the latest Prysm release binary.
+# Usage: ./prysm.sh PROCESS FLAGS
+#   PROCESS can be one of beacon-chain or validator.
+#   FLAGS are the flags or arguments passed to the PROCESS.
+# Downloaded binaries are saved to ./dist. 
+# Use USE_PRYSM_VERSION to specify a specific release version. 
+#   Example: USE_PRYSM_VERSION=v0.3.3 ./prysm.sh beacon-chain
+
+function color() {
+      # Usage: color "31;5" "string"
+      # Some valid values for color:
+      # - 5 blink, 1 strong, 4 underlined
+      # - fg: 31 red,  32 green, 33 yellow, 34 blue, 35 purple, 36 cyan, 37 white
+      # - bg: 40 black, 41 red, 44 blue, 45 purple
+      printf '\033[%sm%s\033[0m\n' "$@"
+}
+
+# `readlink -f` that works on OSX too.
+function get_realpath() {
+    if [ "$(uname -s)" == "Darwin" ]; then
+        local queue="$1"
+        if [[ "${queue}" != /* ]] ; then
+            # Make sure we start with an absolute path.
+            queue="${PWD}/${queue}"
+        fi
+        local current=""
+        while [ -n "${queue}" ]; do
+            # Removing a trailing /.
+            queue="${queue#/}"
+            # Pull the first path segment off of queue.
+            local segment="${queue%%/*}"
+            # If this is the last segment.
+            if [[ "${queue}" != */* ]] ; then
+                segment="${queue}"
+                queue=""
+            else
+                # Remove that first segment.
+                queue="${queue#*/}"
+            fi
+            local link="${current}/${segment}"
+            if [ -h "${link}" ] ; then
+                link="$(readlink "${link}")"
+                queue="${link}/${queue}"
+                if [[ "${link}" == /* ]] ; then
+                    current=""
+                fi
+            else
+                current="${link}"
+            fi
+        done
+
+        echo "${current}"
+    else
+        readlink -f "$1"
+    fi
+}
+
+# Complain if no arguments were provided.
+if [ "$#" -lt 1 ]; then
+    color "31" "Usage: ./prysm.sh PROCESS FLAGS."
+    color "31" "PROCESS can be beacon-chain or validator."
+    exit 1
+fi
+
+
+readonly wrapper_dir="$(dirname "$(get_realpath "${BASH_SOURCE[0]}")")/dist"
+arch=$(uname -m)
+arch=${arch/x86_64/amd64}
+arch=${arch/aarch64/arm64}
+readonly os_arch_suffix="$(uname -s | tr '[:upper:]' '[:lower:]')-$arch"
+
+mkdir -p $wrapper_dir
+
+function get_prysm_version() {
+  if [[ -n ${USE_PRYSM_VERSION:-} ]]; then
+    readonly reason="specified in \$USE_PRYSM_VERSION"
+    readonly prysm_version="${USE_PRYSM_VERSION}"
+  else
+    # Find the latest Prysm version available for download.
+    readonly reason="automatically selected latest available version"
+    prysm_version=$(curl -s https://api.github.com/repos/prysmaticlabs/prysm/releases/latest | grep "tag_name" | cut -d : -f 2,3 | tr -d \" | tr -d , | tr -d [:space:])
+    readonly prysm_version
+  fi
+}
+
+get_prysm_version
+
+color "37" "Latest Prysm version is $prysm_version."
+
+BEACON_CHAIN_REAL="${wrapper_dir}/beacon-chain-${prysm_version}-${os_arch_suffix}"
+VALIDATOR_REAL="${wrapper_dir}/validator-${prysm_version}-${os_arch_suffix}"
+
+if [[ ! -x $BEACON_CHAIN_REAL ]]; then 
+    color "34" "Downloading beacon chain@${prysm_version} to ${BEACON_CHAIN_REAL} (${reason})"
+
+    curl -L "https://github.com/prysmaticlabs/prysm/releases/download/${prysm_version}/beacon-chain-${prysm_version}-${os_arch_suffix}" -o $BEACON_CHAIN_REAL
+    chmod +x $BEACON_CHAIN_REAL
+else
+    color "37" "Beacon chain is up to date."
+fi
+
+if [[ ! -x $VALIDATOR_REAL ]]; then 
+    color "34" "Downloading validator@${prysm_version} to ${VALIDATOR_REAL} (${reason})"
+
+    curl -L "https://github.com/prysmaticlabs/prysm/releases/download/${prysm_version}/validator-${prysm_version}-${os_arch_suffix}" -o $VALIDATOR_REAL
+    chmod +x $VALIDATOR_REAL
+else
+    color "37" "Validator is up to date."
+fi
+
+case $1 in
+  beacon-chain)
+    readonly process=$BEACON_CHAIN_REAL
+    ;;
+
+  validator)
+    readonly process=$VALIDATOR_REAL
+    ;;
+
+  *)
+    color "31" "Usage: ./prysm.sh PROCESS FLAGS."
+    color "31" "PROCESS can be beacon-chain or validator."
+    ;;
+esac
+
+color "36" "Starting Prysm $1 ${@:2}"
+exec -a "$0" "${process}" "${@:2}"