// strAttack.go
package timeAttack

import (
    "fmt"
    "math/rand"
    "sort"
    "time"
)

const SECRET = "s3cr3t_k3y"

// Use a sink variable — prevents compiler from optimizing away the work loop
var sink int

func vulnerableCheck(input string) bool {
    if len(input) != len(SECRET) {
       return false
    }
    for i := 0; i < len(SECRET); i++ {
       if input[i] != SECRET[i] {
          return false
       }
       // sink prevents dead-code elimination by the compiler
       for j := 0; j < 1000; j++ {
          sink += j
       }
    }
    return true
}

func measureTime(input string, trialsCount int) time.Duration {
    samples := make([]int64, trialsCount)
    for i := 0; i < trialsCount; i++ {
       start := time.Now()
       vulnerableCheck(input)
       samples[i] = time.Since(start).Nanoseconds()
    }
    sort.Slice(samples, func(i, j int) bool { return samples[i] < samples[j] })
    // lower quartile — stable against GC/scheduler spikes
    return time.Duration(samples[trialsCount/4])
}

func Attack(guessedLength int) string {
    const trials = 3_000
    charset := "abcdefghijklmnopqrstuvwxyz0123456789_!ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    recovered := make([]byte, guessedLength)

    for i := range recovered {
       recovered[i] = 'a'
    }

    for index := 0; index < guessedLength; index++ {
       fmt.Printf("Cracking position %d... ", index)

       bestChar := charset[0]
       bestTime := time.Duration(0)
       first := true

       // Shuffle charset order to avoid positional bias
       order := rand.Perm(len(charset))

       for _, ci := range order {
          recovered[index] = charset[ci]
          elapsed := measureTime(string(recovered), trials)

          if first || elapsed > bestTime {
             bestTime = elapsed
             bestChar = charset[ci]
             first = false
          }
       }

       recovered[index] = bestChar
       fmt.Printf("found '%c' (signal: %v) → recovered so far: %s\n",
          bestChar, bestTime, string(recovered[:index+1]))
    }

    return string(recovered)
}

// main.go
package main

import (
    "fmt"
    "practice/timeAttack"
)

func main() {
    fmt.Println("=== Timing Attack Demo ===")

    for i := 1; i < 11; i++ {

       fmt.Printf("Secret length is known (or guessed): %d\n\n", i)

       result := timeAttack.Attack(i)

       fmt.Println()
       if result == timeAttack.SECRET {
          fmt.Printf(":) Secret recovered: \"%s\"\n", result)
          break
       } else {
          fmt.Printf(":( Got: \"%s\" (close but timing noise interfered)\n", result)
          fmt.Println("   Run again — noise can cause misses on a busy system.")
       }

    }

}