package main

import (
	"crypto/sha256"
	"fmt"
	"net/http"
	"strconv"
	"sync"
	"time"
)

var BuildTime string

const ramChunkSize = 100 * 1024 * 1024 // 0.1 GiB

var (
	ramMu     sync.Mutex
	ramChunks [][]byte
)

func main() {
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
		_, _ = fmt.Fprintln(w, BuildTime)
	})
	http.HandleFunc("/ram", func(w http.ResponseWriter, r *http.Request) {
		chunk := make([]byte, ramChunkSize)
		for i := range chunk {
			chunk[i] = 1
		}
		ramMu.Lock()
		ramChunks = append(ramChunks, chunk)
		total := len(ramChunks)
		ramMu.Unlock()

		w.WriteHeader(http.StatusOK)
		_, _ = fmt.Fprintf(w, "allocated 0.1 GiB, total held: %.1f GiB (%d chunks)\n", float64(total)*0.1, total)
	})
	http.HandleFunc("/cpu", func(w http.ResponseWriter, r *http.Request) {
		iterations := 1_000_000
		if n, err := strconv.Atoi(r.URL.Query().Get("n")); err == nil && n > 0 {
			iterations = n
		}

		start := time.Now()
		sum := sha256.Sum256([]byte("zerops"))
		for i := 0; i < iterations; i++ {
			sum = sha256.Sum256(sum[:])
		}
		elapsed := time.Since(start)

		w.WriteHeader(http.StatusOK)
		_, _ = fmt.Fprintf(w, "computed %x in %s (%d iterations)\n", sum, elapsed, iterations)
	})
	_ = http.ListenAndServe(":8080", nil)
}