Add option to auto-fetch puzzle input

Author: terminalnode

.gitignore

@@ -1,7 +1,12 @@
 input/*
 !input/.gitkeep
 
+!input/cache/
+input/cache/*
+!input/cache/.gitkeep
+
 build/*
 !build/.gitkeep
 
 .idea
+client-env.sh

README.md

@@ -17,6 +17,11 @@ run the solution.
 If you don't want to use the client, curl is also an option:
 `curl -X POST --data-binary @INPUT_FILE http://localhost/DAY/PART`
 
+### Auto-fetch puzzle input
+If you copy the file `./client-env.sh.example` to `./client-env.sh` and fill in your
+session token, the client (when running `./client.sh`) can auto-fetch your puzzle
+input. You can then run the client as only `./client.sh -day DAY -part PART`.
+
 ### Running in Kubernetes
 * Install `minikube` and run `./k8s/start-minikube.sh` to create the `aoc2024` cluster.
 * Then run `./k8s/build.sh all` to build all the docker images, making them available

client-env.sh.example

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+# Copy this file as `client-env.sh`, removing the `.example` suffix.
+#
+# To get the session token, inspect the requests sent to AoC and copy the Cookie-field of the request.
+# Instructions here: https://github.com/wimglenn/advent-of-code-wim/issues/1
+# Then remove the 'session=' from the beginning of the cookie.
+export AOC2024_INPUT_CACHE_PATH='./input/cache'
+export AOC2024_SESSION_TOKEN='insert-token-here'

client.sh

@@ -3,6 +3,11 @@
 # a binary file
 profile_name='aoc2024'
 url='localhost'
+env_file='./client-env.sh'
+
+if [ -f "$env_file" ]; then
+    source "$env_file"
+fi
 
 if [ -n "$(command -v minikube)" ] && minikube profile list | grep -q "$profile_name"; then
   echo "Minikube is installed and profile '$profile_name' exists, using minikube ip ($(minikube ip))."

client/run.go

@@ -24,12 +24,21 @@ func runCmd(args []string) {
 
 	validateDayAndPart(*day, *part)
 
+	sessionToken := os.Getenv("AOC2024_SESSION_TOKEN")
+
 	var input string
 	switch {
 	case *file != "":
 		input = readFile(*file)
+	case sessionToken != "":
+		data, err := fetchInput(*day, sessionToken)
+		if err != nil {
+			fmt.Printf("Failed to fetch input using session token '%s': %v", sessionToken, err)
+			os.Exit(1)
+		}
+		input = data
 	default:
-		fmt.Printf("No input method selected, can't get puzzle input.\n")
+		fmt.Println("No input method selected and session token not set, can't get puzzle input.")
 		os.Exit(1)
 	}
 

client/utils.go

@@ -4,21 +4,79 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"net/http"
 	"os"
+	"strings"
 )
 
 func readFile(path string) string {
-	data, err := os.ReadFile(path)
+	data, err := readFileSafely(path)
 	if err != nil {
-		fmt.Printf("Failed to read file '%s' with error: %v\n", path, err)
+		fmt.Print(err.Error())
 		os.Exit(1)
 	}
+	return data
+}
+
+func readFileSafely(path string) (string, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return "", fmt.Errorf("failed to read file '%s' with error: %v", path, err)
+	}
 
 	buff := bytes.NewBuffer(data)
-	input, err := io.ReadAll(buff)
+	content, err := io.ReadAll(buff)
 	if err != nil {
-		fmt.Printf("Failed to parse data from file '%s' with error: %v\n", path, err)
+		return "", fmt.Errorf("failed to parse data from file '%s' with error: %v", path, err)
+	}
+
+	return string(content), nil
+}
+
+func saveFileSafely(path string, content string) error {
+	err := os.WriteFile(path, []byte(content), 0744)
+	return err
+}
+
+func fetchInput(
+	day int,
+	sessionToken string,
+) (string, error) {
+	cachePath := os.Getenv("AOC2024_INPUT_CACHE_PATH")
+	var cacheFile string
+	cacheEnabled := false
+	if cachePath != "" {
+		cacheEnabled = true
+		cacheFile = fmt.Sprintf("%s/day%d-%s", cachePath, day, sessionToken)
+
+		content, err := readFileSafely(cacheFile)
+		if err == nil {
+			return content, nil
+		}
+	}
+
+	url := fmt.Sprintf("https://adventofcode.com/2024/day/%d/input", day)
+	req, err := http.NewRequest("GET", url, bytes.NewBuffer([]byte{}))
+	if err != nil {
+		return "", err
+	}
+	req.Header.Set("Cookie", fmt.Sprintf("session=%s", sessionToken))
+
+	client := &http.Client{}
+	resp, err := client.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", err
+	}
+	strBody, _ := strings.CutSuffix(string(body), "\n")
+
+	if cacheEnabled {
+		_ = saveFileSafely(cacheFile, strBody)
 	}
 
-	return string(input)
+	return strBody, nil
 }