github_fetchfile

#!/usr/bin/env bash
###############################################################################
## File: github_fetchfile
## Purpose: Shell Script to curl-download large files from github
## Notes:
## - Will use your Github CLI Token from the macOS Keychain
## - Has to hit the repo twice, once to get the SHA needed, and once to
##   actually download your file. See instead github_fetchfile_small if < 1MB
## - Depends on node for JSON parsing.
###############################################################################

set -e

while getopts ":t:o:r:b:p:O:s:" opt; do
	case $opt in
		t) TOKEN="$OPTARG"
		;;
		s) SCRIPT_NAME="$OPTARG"
		;;
		o) REPO_OWNER="$OPTARG"
		;;
		r) REPO="$OPTARG"
		;;
		b) BRANCH="$OPTARG"
		;;
		p) ASSET_PATH="$OPTARG"
		;;
		O) OUTPUT_PATH="$OPTARG"
		;;
		\?) INVALID=1; echo "Invalid Option: -$OPTARG" >&2
		;;
	esac
done

INVALID=${INVALID:-0}

# Set Defaults
REPO_OWNER=${REPO_OWNER:-"$GITHUB_USER"}
BRANCH=${BRANCH:-"main"}
# Used to get a unique access code for this script
SCRIPT_NAME=${SCRIPT_NAME:-"$(basename "$0")"}

# Test required params
if [[ INVALID -eq 0 ]] && [[ "$REPO_OWNER" == "" ]]; then
	echo "Repository owner must be passed in, or ENV[\$GITHUB_USER] must be set!" >&2
	INVALID=1
fi

TOKEN=$("$(dirname "${BASH_SOURCE[0]}" )/github_token" -r -s "$SCRIPT_NAME")
if [[ INVALID -eq 0 ]] && [[ "$TOKEN" == "" ]]; then
	echo "Couldn't load Github Personal Access Token, aborting… " >&2
	exit 1
fi

if [[ INVALID -eq 0 ]] && [[ "$ASSET_PATH" == "" ]]; then
	echo "-p ASSET_PATH missing." >&2
	INVALID=1
fi
if [[ INVALID -eq 0 ]] && [[ "$OUTPUT_PATH" == "" ]]; then
	echo "-O OUTPUT_PATH missing." >&2
	INVALID=1
fi

if [ $INVALID -eq 1 ]; then
	echo "Usage: $0 [-t TOKEN] [-s SCRIPT_NAME] [-o REPO_OWNER] -r REPO [-b BRANCH] -p ASSET_PATH -O OUTPUT_PATH" >&2
	echo " -t Github Personal Access Token with sufficient permissions. Will look at keychain if omitted." >&2
	echo " -s Identifier for the Keychain item used to lookup a token for this script." >&2
	echo " -b Choose what branch to fetch from. If omitted, the default branch name is 'main'." >&2
	exit 1
fi

type node >/dev/null 2>&1 || { echo >&2 "This tool requires node for JSON parsing/inspection. Aborting."; exit 1; }

# Technique from: https://medium.com/@caludio/how-to-download-large-files-from-github-4863a2dbba3b

# 1. Fetch the dir of the target
echo "https://api.github.com/repos/$REPO_OWNER/$REPO/contents/$(basename "$ASSET_PATH")?ref=$BRANCH"
JSON_RESPONSE=$(curl -H "Authorization: token $TOKEN" -L "https://api.github.com/repos/$REPO_OWNER/$REPO/contents/$(dirname "$ASSET_PATH")?ref=$BRANCH")
# echo "$JSON_RESPONSE"

# 2. Parse the JSON of the dir and find the file we were looking for
BASE=$(basename "$ASSET_PATH")
# echo "Base $BASE"

SCRIPT=$(cat <<- HEREDOC
	var r=JSON.parse('${JSON_RESPONSE}');
	r.forEach(function(v) {
		if(v.name=='${BASE}'){
			console.log(v.sha);
		}
	});
HEREDOC
)

THE_SHA=$(echo "$SCRIPT" | tr -d '\n' | tr -d '\t' | node)
# echo "$SHA"

# 3. Fetch the large file
curl -s -H "Authorization: token $TOKEN" \
	-H "Accept: application/vnd.github.v3.raw+json" \
	-o "$OUTPUT_PATH" -L "https://api.github.com/repos/$REPO_OWNER/$REPO/git/blobs/$THE_SHA"