/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "benchmark.h"

#include <regex.h>
#include <stdio.h>
#include <stdlib.h>

#include <string>
#include <map>

static int64_t gBytesProcessed;
static int64_t gBenchmarkTotalTimeNs;
static int64_t gBenchmarkStartTimeNs;

typedef std::map<std::string, ::testing::Benchmark*> BenchmarkMap;
typedef BenchmarkMap::iterator BenchmarkMapIt;
static BenchmarkMap gBenchmarks;

static int Round(int n) {
  int base = 1;
  while (base*10 < n) {
    base *= 10;
  }
  if (n < 2*base) {
    return 2*base;
  }
  if (n < 5*base) {
    return 5*base;
  }
  return 10*base;
}

static int64_t NanoTime() {
  struct timespec t;
  t.tv_sec = t.tv_nsec = 0;
  clock_gettime(CLOCK_MONOTONIC, &t);
  return static_cast<int64_t>(t.tv_sec) * 1000000000LL + t.tv_nsec;
}

namespace testing {

Benchmark* Benchmark::Arg(int arg) {
  args_.push_back(arg);
  return this;
}

bool Benchmark::ShouldRun(int argc, char* argv[]) {
  if (argc == 1) {
    return true;  // With no arguments, we run all benchmarks.
  }
  // Otherwise, we interpret each argument as a regular expression and
  // see if any of our benchmarks match.
  for (int i = 1; i < argc; i++) {
    regex_t re;
    if (regcomp(&re, argv[i], 0) != 0) {
      fprintf(stderr, "couldn't compile \"%s\" as a regular expression!\n", argv[i]);
      exit(EXIT_FAILURE);
    }
    int match = regexec(&re, name_, 0, NULL, 0);
    regfree(&re);
    if (match != REG_NOMATCH) {
      return true;
    }
  }
  return false;
}

void Benchmark::Register(const char* name, void (*fn)(int), void (*fn_range)(int, int)) {
  name_ = name;
  fn_ = fn;
  fn_range_ = fn_range;

  if (fn_ == NULL && fn_range_ == NULL) {
    fprintf(stderr, "%s: missing function\n", name_);
    exit(EXIT_FAILURE);
  }

  gBenchmarks.insert(std::make_pair(name, this));
}

void Benchmark::Run() {
  if (args_.empty()) {
    fprintf(stderr, "%s: no args!\n", name_);
    exit(EXIT_FAILURE);
  }
  for (size_t i = 0; i < args_.size(); ++i) {
    RunWithArg(args_[i]);
  }
}

void Benchmark::RunRepeatedlyWithArg(int iterations, int arg) {
  gBytesProcessed = 0;
  gBenchmarkTotalTimeNs = 0;
  gBenchmarkStartTimeNs = NanoTime();
  if (fn_ != NULL) {
    fn_(iterations);
  } else {
    fn_range_(iterations, arg);
  }
  if (gBenchmarkStartTimeNs != 0) {
    gBenchmarkTotalTimeNs += NanoTime() - gBenchmarkStartTimeNs;
  }
}

void Benchmark::RunWithArg(int arg) {
  // run once in case it's expensive
  int iterations = 1;
  RunRepeatedlyWithArg(iterations, arg);
  while (gBenchmarkTotalTimeNs < 1e9 && iterations < 1e9) {
    int last = iterations;
    if (gBenchmarkTotalTimeNs/iterations == 0) {
      iterations = 1e9;
    } else {
      iterations = 1e9 / (gBenchmarkTotalTimeNs/iterations);
    }
    iterations = std::max(last + 1, std::min(iterations + iterations/2, 100*last));
    iterations = Round(iterations);
    RunRepeatedlyWithArg(iterations, arg);
  }

  char throughput[100];
  throughput[0] = '\0';
  if (gBenchmarkTotalTimeNs > 0 && gBytesProcessed > 0) {
    double mib_processed = static_cast<double>(gBytesProcessed)/1e6;
    double seconds = static_cast<double>(gBenchmarkTotalTimeNs)/1e9;
    snprintf(throughput, sizeof(throughput), " %8.2f MiB/s", mib_processed/seconds);
  }

  char full_name[100];
  if (fn_range_ != NULL) {
    if (arg >= (1<<20)) {
      snprintf(full_name, sizeof(full_name), "%s/%dM", name_, arg/(1<<20));
    } else if (arg >= (1<<10)) {
      snprintf(full_name, sizeof(full_name), "%s/%dK", name_, arg/(1<<10));
    } else {
      snprintf(full_name, sizeof(full_name), "%s/%d", name_, arg);
    }
  } else {
    snprintf(full_name, sizeof(full_name), "%s", name_);
  }

  printf("%-20s %10lld %10lld%s\n", full_name,
         static_cast<int64_t>(iterations), gBenchmarkTotalTimeNs/iterations, throughput);
  fflush(stdout);
}

}  // namespace testing

void SetBenchmarkBytesProcessed(int64_t x) {
  gBytesProcessed = x;
}

void StopBenchmarkTiming() {
  if (gBenchmarkStartTimeNs != 0) {
    gBenchmarkTotalTimeNs += NanoTime() - gBenchmarkStartTimeNs;
  }
  gBenchmarkStartTimeNs = 0;
}

void StartBenchmarkTiming() {
  if (gBenchmarkStartTimeNs == 0) {
    gBenchmarkStartTimeNs = NanoTime();
  }
}

int main(int argc, char* argv[]) {
  if (gBenchmarks.empty()) {
    fprintf(stderr, "no benchmarks!\n");
    exit(EXIT_FAILURE);
  }

  printf("%-20s %10s %10s\n", "", "iterations", "ns/op");
  fflush(stdout);

  for (BenchmarkMapIt it = gBenchmarks.begin(); it != gBenchmarks.end(); ++it) {
    ::testing::Benchmark* b = it->second;
    if (b->ShouldRun(argc, argv)) {
      b->Run();
    }
  }
  return 0;
}