// Copyright 2017-2020 The Verible Authors.
//
// 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.

#ifndef VERIBLE_COMMON_UTIL_LOGGING_H_
#define VERIBLE_COMMON_UTIL_LOGGING_H_

#include <atomic>
#include <cstdint>
#include <limits>
#include <memory>
#include <sstream>
#include <string>

#include "absl/base/log_severity.h"
#include "absl/base/optimization.h"
#include "absl/strings/string_view.h"

// Prevent this Windows.h #define from leaking out of our headers.
#undef ERROR

namespace verible {
const int INFO = 0;            // base_logging::INFO;
const int WARNING = 1;         // base_logging::WARNING;
const int ERROR = 2;           // base_logging::ERROR;
const int FATAL = 3;           // base_logging::FATAL;
const int NUM_SEVERITIES = 4;  // base_logging::NUM_SEVERITIES;

namespace internal {

class LogMessage : public std::basic_ostringstream<char> {
 public:
  LogMessage(const char* fname, int line, int severity);
  ~LogMessage() override;

  // Returns the minimum log level for VLOG statements.
  // E.g., if MinVLogLevel() is 2, then VLOG(2) statements will produce output,
  // but VLOG(3) will not. Defaults to 0.
  static int64_t MinVLogLevel();

  // Returns whether VLOG level lvl is activated for the file fname.
  //
  // E.g. if the environment variable VERIBLE_CPP_VMODULE contains foo=3 and
  // fname is foo.cc and lvl is <= 3, this will return true. It will also return
  // true if the level is lower or equal to VERIBLE_CPP_MIN_VLOG_LEVEL (default
  // zero).
  //
  // It is expected that the result of this query will be cached in the VLOG-ing
  // call site to avoid repeated lookups. This routine performs a hash-map
  // access against the VLOG-ing specification provided by the env var.
  static bool VmoduleActivated(const char* fname, int level);

 protected:
  void GenerateLogMessage();

 private:
  const char* fname_;
  int line_;
  int severity_;
};

// Uses the lower operator & precedence to voidify a LogMessage reference, so
// that the ternary VLOG() implementation is balanced, type wise.
struct Voidifier {
  template <typename T>
  void operator&(const T&) const {}
};

// LogMessageFatal ensures the process will exit in failure after
// logging this message.
class LogMessageFatal : public LogMessage {
 public:
  LogMessageFatal(const char* file, int line) ABSL_ATTRIBUTE_COLD;
  ABSL_ATTRIBUTE_NORETURN ~LogMessageFatal() override;
};

// LogMessageNull supports the DVLOG macro by simply dropping any log messages.
class LogMessageNull : public std::basic_ostringstream<char> {
 public:
  LogMessageNull() {}
  ~LogMessageNull() override {}
};

#define _VERIBLE_LOG_INFO \
  ::verible::internal::LogMessage(__FILE__, __LINE__, ::verible::INFO)
#define _VERIBLE_LOG_WARNING \
  ::verible::internal::LogMessage(__FILE__, __LINE__, ::verible::WARNING)
#define _VERIBLE_LOG_ERROR \
  ::verible::internal::LogMessage(__FILE__, __LINE__, ::verible::ERROR)
#define _VERIBLE_LOG_FATAL \
  ::verible::internal::LogMessageFatal(__FILE__, __LINE__)

#define LOG(severity) _VERIBLE_LOG_##severity
#define _VERIBLE_LOG_QFATAL _VERIBLE_LOG_FATAL

// Otherwise, set VERIBLE_CPP_MIN_VLOG_LEVEL environment to update minimum log
// level of VLOG, or VERIBLE_CPP_VMODULE to set the minimum log level for
// individual translation units.
#define VLOG_IS_ON(lvl)                                                  \
  (([](int level, const char* fname) {                                   \
    static const bool vmodule_activated =                                \
        ::verible::internal::LogMessage::VmoduleActivated(fname, level); \
    return vmodule_activated;                                            \
  })(lvl, __FILE__))

#define VLOG(level)                     \
  ABSL_PREDICT_TRUE(!VLOG_IS_ON(level)) \
  ? (void)0                             \
  : ::verible::internal::Voidifier() &  \
          ::verible::internal::LogMessage(__FILE__, __LINE__, verible::INFO)

// `DVLOG` behaves like `VLOG` in debug mode (i.e. `#ifndef NDEBUG`).
// Otherwise, it compiles away and does nothing.
#ifndef NDEBUG
#define DVLOG VLOG
#else
#define DVLOG(verbose_level) \
  while (false && (verbose_level) > 0) ::verible::internal::LogMessageNull()
#endif

class LogEveryNState {
 public:
  bool ShouldLog(int n);
  uint32_t counter() { return counter_.load(std::memory_order_relaxed); }

 private:
  std::atomic<uint32_t> counter_{0};
};

class LogFirstNState {
 public:
  bool ShouldLog(int n);
  uint32_t counter() { return counter_.load(std::memory_order_relaxed); }

 private:
  std::atomic<uint32_t> counter_{0};
};

class LogEveryPow2State {
 public:
  bool ShouldLog(int ignored);
  uint32_t counter() { return counter_.load(std::memory_order_relaxed); }

 private:
  std::atomic<uint32_t> counter_{0};
};

class LogEveryNSecState {
 public:
  bool ShouldLog(double seconds);
  uint32_t counter() { return counter_.load(std::memory_order_relaxed); }

 private:
  std::atomic<uint32_t> counter_{0};
  // Cycle count according to CycleClock that we should next log at.
  std::atomic<int64_t> next_log_time_cycles_{0};
};

// This macro has a lot going on!
//
// * A local static (`logging_internal_stateful_condition_state`) is
//   declared in a scope such that each `LOG_EVERY_N` (etc.) line has its own
//   state.
// * `COUNTER`, the third variable, is used to support `<< COUNTER`. It is not
//   mangled, so shadowing can be a problem, albeit more of a
//   shoot-yourself-in-the-foot one.  Don't name your variables `COUNTER`.
// * A single for loop can declare state and also test
//   `condition && state.ShouldLog()`, but there's no way to constrain it to run
//   only once (or not at all) without declaring another variable.  The outer
//   for-loop declares this variable (`do_log`).
// * Using for loops instead of if statements means there's no risk of an
//   ambiguous dangling else statement.
#define LOGGING_INTERNAL_STATEFUL_CONDITION(kind, condition, arg)   \
  for (bool logging_internal_stateful_condition_do_log(condition);  \
       logging_internal_stateful_condition_do_log;                  \
       logging_internal_stateful_condition_do_log = false)          \
    for (static ::verible::internal::Log##kind##State               \
             logging_internal_stateful_condition_state;             \
         logging_internal_stateful_condition_do_log &&              \
         logging_internal_stateful_condition_state.ShouldLog(arg);  \
         logging_internal_stateful_condition_do_log = false)        \
      for (const uint32_t COUNTER ABSL_ATTRIBUTE_UNUSED =           \
               logging_internal_stateful_condition_state.counter(); \
           logging_internal_stateful_condition_do_log;              \
           logging_internal_stateful_condition_do_log = false)

// An instance of `LOG_EVERY_N` increments a hidden zero-initialized counter
// every time execution passes through it and logs the specified message when
// the counter's value is a multiple of `n`, doing nothing otherwise.  Each
// instance has its own counter.  The counter's value can be logged by streaming
// the symbol `COUNTER`.  `LOG_EVERY_N` is thread-safe.
// Example:
//
//   for (const auto& user : all_users) {
//     LOG_EVERY_N(INFO, 1000) << "Processing user #" << COUNTER;
//     ProcessUser(user);
//   }
#define LOG_EVERY_N(severity, n)                       \
  LOGGING_INTERNAL_STATEFUL_CONDITION(EveryN, true, n) \
  LOG(severity)
// `LOG_FIRST_N` behaves like `LOG_EVERY_N` except that the specified message is
// logged when the counter's value is less than `n`.  `LOG_FIRST_N` is
// thread-safe.
#define LOG_FIRST_N(severity, n)                       \
  LOGGING_INTERNAL_STATEFUL_CONDITION(FirstN, true, n) \
  LOG(severity)
// `LOG_EVERY_POW_2` behaves like `LOG_EVERY_N` except that the specified
// message is logged when the counter's value is a power of 2.
// `LOG_EVERY_POW_2` is thread-safe.
#define LOG_EVERY_POW_2(severity)                         \
  LOGGING_INTERNAL_STATEFUL_CONDITION(EveryPow2, true, 0) \
  LOG(severity)
// An instance of `LOG_EVERY_N_SEC` uses a hidden state variable to log the
// specified message at most once every `n_seconds`.  A hidden counter of
// executions (whether a message is logged or not) is also maintained and can be
// logged by streaming the symbol `COUNTER`.  `LOG_EVERY_N_SEC` is thread-safe.
// Example:
//
//   LOG_EVERY_N_SEC(INFO, 2.5) << "Got " << COUNTER << " cookies so far";
#define LOG_EVERY_N_SEC(severity, n_seconds)                      \
  LOGGING_INTERNAL_STATEFUL_CONDITION(EveryNSec, true, n_seconds) \
  LOG(severity)

// CHECK dies with a fatal error if condition is not true.  It is *not*
// controlled by NDEBUG, so the check will be executed regardless of
// compilation mode.  Therefore, it is safe to do things like:
//    CHECK(fp->Write(x) == 4)
#define CHECK(condition)                \
  if (ABSL_PREDICT_FALSE(!(condition))) \
  _VERIBLE_LOG_FATAL << "Check failed: " #condition " "

// Function is overloaded for integral types to allow static const
// integrals declared in classes and not defined to be used as arguments to
// CHECK* macros. It's not encouraged though.
template <typename T>
inline const T& GetReferenceableValue(const T& t) {
  return t;
}
inline char GetReferenceableValue(char t) { return t; }
inline unsigned char GetReferenceableValue(unsigned char t) { return t; }
inline signed char GetReferenceableValue(signed char t) { return t; }
inline int16_t GetReferenceableValue(int16_t t) { return t; }
inline uint16_t GetReferenceableValue(uint16_t t) { return t; }
inline int GetReferenceableValue(int t) { return t; }
inline unsigned int GetReferenceableValue(unsigned int t) { return t; }
inline int64_t GetReferenceableValue(int64_t t) { return t; }
inline uint64_t GetReferenceableValue(uint64_t t) { return t; }

// This formats a value for a failing CHECK_XX statement.  Ordinarily,
// it uses the definition for operator<<, with a few special cases below.
template <typename T>
inline void MakeCheckOpValueString(std::ostream* os, const T& v) {
  (*os) << v;
}

// Overrides for char types provide readable values for unprintable
// characters.
template <>
void MakeCheckOpValueString(std::ostream* os, const char& v);
template <>
void MakeCheckOpValueString(std::ostream* os, const signed char& v);
template <>
void MakeCheckOpValueString(std::ostream* os, const unsigned char& v);

// We need an explicit specialization for std::nullptr_t.
template <>
void MakeCheckOpValueString(std::ostream* os, const std::nullptr_t& p);

// A container for a string pointer which can be evaluated to a bool -
// true iff the pointer is non-NULL.
struct CheckOpString {
  CheckOpString(std::string* str) : str_(str) {}
  // No destructor: if str_ is non-NULL, we're about to LOG(FATAL),
  // so there's no point in cleaning up str_.
  operator bool() const { return ABSL_PREDICT_FALSE(str_ != NULL); }
  std::string* str_;
};

// Build the error message string. Specify no inlining for code size.
template <typename T1, typename T2>
std::string* MakeCheckOpString(const T1& v1, const T2& v2,
                               const char* exprtext) ABSL_ATTRIBUTE_NOINLINE;

// A helper class for formatting "expr (V1 vs. V2)" in a CHECK_XX
// statement.  See MakeCheckOpString for sample usage.  Other
// approaches were considered: use of a template method (e.g.,
// base::BuildCheckOpString(exprtext, base::Print<T1>, &v1,
// base::Print<T2>, &v2), however this approach has complications
// related to volatile arguments and function-pointer arguments).
class CheckOpMessageBuilder {
 public:
  // Inserts "exprtext" and " (" to the stream.
  explicit CheckOpMessageBuilder(const char* exprtext);
  // Deletes "stream_".
  ~CheckOpMessageBuilder();
  // For inserting the first variable.
  std::ostream* ForVar1() { return stream_; }
  // For inserting the second variable (adds an intermediate " vs. ").
  std::ostream* ForVar2();
  // Get the result (inserts the closing ")").
  std::string* NewString();

 private:
  std::ostringstream* stream_;
};

template <typename T1, typename T2>
std::string* MakeCheckOpString(const T1& v1, const T2& v2,
                               const char* exprtext) {
  CheckOpMessageBuilder comb(exprtext);
  MakeCheckOpValueString(comb.ForVar1(), v1);
  MakeCheckOpValueString(comb.ForVar2(), v2);
  return comb.NewString();
}

// Helper functions for CHECK_OP macro.
// The (int, int) specialization works around the issue that the compiler
// will not instantiate the template version of the function on values of
// unnamed enum type - see comment below.
// The (size_t, int) and (int, size_t) specialization are to handle unsigned
// comparison errors while still being thorough with the comparison.
#define VERIBLE_DEFINE_CHECK_OP_IMPL(name, op)                           \
  template <typename T1, typename T2>                                    \
  inline std::string* name##Impl(const T1& v1, const T2& v2,             \
                                 const char* exprtext) {                 \
    if (ABSL_PREDICT_TRUE(v1 op v2))                                     \
      return NULL;                                                       \
    else                                                                 \
      return ::verible::internal::MakeCheckOpString(v1, v2, exprtext);   \
  }                                                                      \
  inline std::string* name##Impl(int v1, int v2, const char* exprtext) { \
    return name##Impl<int, int>(v1, v2, exprtext);                       \
  }                                                                      \
  inline std::string* name##Impl(const size_t v1, const int v2,          \
                                 const char* exprtext) {                 \
    if (ABSL_PREDICT_FALSE(v2 < 0)) {                                    \
      return ::verible::internal::MakeCheckOpString(v1, v2, exprtext);   \
    }                                                                    \
    return name##Impl<size_t, size_t>(v1, v2, exprtext);                 \
  }                                                                      \
  inline std::string* name##Impl(const int v1, const size_t v2,          \
                                 const char* exprtext) {                 \
    const size_t max_compare = std::numeric_limits<int>::max();          \
    if (ABSL_PREDICT_FALSE(v2 >= max_compare)) {                         \
      return ::verible::internal::MakeCheckOpString(v1, v2, exprtext);   \
    }                                                                    \
    const size_t uval = (size_t)((unsigned)v2);                          \
    return name##Impl<size_t, size_t>(v1, uval, exprtext);               \
  }

// We use the full name Check_EQ, Check_NE, etc. in case the file including
// base/logging.h provides its own #defines for the simpler names EQ, NE, etc.
// This happens if, for example, those are used as token names in a
// yacc grammar.
VERIBLE_DEFINE_CHECK_OP_IMPL(Check_EQ,
                             ==)  // Compilation error with CHECK_EQ(NULL, x)?
VERIBLE_DEFINE_CHECK_OP_IMPL(Check_NE, !=)  // Use CHECK(x == NULL) instead.
VERIBLE_DEFINE_CHECK_OP_IMPL(Check_LE, <=)
VERIBLE_DEFINE_CHECK_OP_IMPL(Check_LT, <)
VERIBLE_DEFINE_CHECK_OP_IMPL(Check_GE, >=)
VERIBLE_DEFINE_CHECK_OP_IMPL(Check_GT, >)
#undef VERIBLE_DEFINE_CHECK_OP_IMPL

// In optimized mode, use CheckOpString to hint to compiler that
// the while condition is unlikely.
#define CHECK_OP_LOG(name, op, val1, val2)                         \
  while (::verible::internal::CheckOpString _result =              \
             ::verible::internal::name##Impl(                      \
                 ::verible::internal::GetReferenceableValue(val1), \
                 ::verible::internal::GetReferenceableValue(val2), \
                 #val1 " " #op " " #val2))                         \
  ::verible::internal::LogMessageFatal(__FILE__, __LINE__) << *(_result.str_)

#define CHECK_OP(name, op, val1, val2) CHECK_OP_LOG(name, op, val1, val2)

// CHECK_EQ/NE/...
#define CHECK_EQ(val1, val2) CHECK_OP(Check_EQ, ==, val1, val2)
#define CHECK_NE(val1, val2) CHECK_OP(Check_NE, !=, val1, val2)
#define CHECK_LE(val1, val2) CHECK_OP(Check_LE, <=, val1, val2)
#define CHECK_LT(val1, val2) CHECK_OP(Check_LT, <, val1, val2)
#define CHECK_GE(val1, val2) CHECK_OP(Check_GE, >=, val1, val2)
#define CHECK_GT(val1, val2) CHECK_OP(Check_GT, >, val1, val2)
#define CHECK_NOTNULL(val)                              \
  ::verible::internal::CheckNotNull(__FILE__, __LINE__, \
                                    "'" #val "' Must be non NULL", (val))

#ifndef NDEBUG
// DCHECK_EQ/NE/...
#define DCHECK(condition) CHECK(condition)
#define DCHECK_EQ(val1, val2) CHECK_EQ(val1, val2)
#define DCHECK_NE(val1, val2) CHECK_NE(val1, val2)
#define DCHECK_LE(val1, val2) CHECK_LE(val1, val2)
#define DCHECK_LT(val1, val2) CHECK_LT(val1, val2)
#define DCHECK_GE(val1, val2) CHECK_GE(val1, val2)
#define DCHECK_GT(val1, val2) CHECK_GT(val1, val2)

#else

#define DCHECK(condition) \
  while (false && (condition)) LOG(FATAL)

// NDEBUG is defined, so DCHECK_EQ(x, y) and so on do nothing.
// However, we still want the compiler to parse x and y, because
// we don't want to lose potentially useful errors and warnings.
// _DCHECK_NOP is a helper, and should not be used outside of this file.
#define _VERIBLE_DCHECK_NOP(x, y) \
  while (false && ((void)(x), (void)(y), 0)) LOG(FATAL)

#define DCHECK_EQ(x, y) _VERIBLE_DCHECK_NOP(x, y)
#define DCHECK_NE(x, y) _VERIBLE_DCHECK_NOP(x, y)
#define DCHECK_LE(x, y) _VERIBLE_DCHECK_NOP(x, y)
#define DCHECK_LT(x, y) _VERIBLE_DCHECK_NOP(x, y)
#define DCHECK_GE(x, y) _VERIBLE_DCHECK_NOP(x, y)
#define DCHECK_GT(x, y) _VERIBLE_DCHECK_NOP(x, y)

#endif

// These are for when you don't want a CHECK failure to print a verbose
// stack trace.  The implementation of CHECK* in this file already doesn't.
#define QCHECK(condition) CHECK(condition)
#define QCHECK_EQ(x, y) CHECK_EQ(x, y)
#define QCHECK_NE(x, y) CHECK_NE(x, y)
#define QCHECK_LE(x, y) CHECK_LE(x, y)
#define QCHECK_LT(x, y) CHECK_LT(x, y)
#define QCHECK_GE(x, y) CHECK_GE(x, y)
#define QCHECK_GT(x, y) CHECK_GT(x, y)

template <typename T>
T&& CheckNotNull(const char* file, int line, const char* exprtext, T&& t) {
  if (t == nullptr) {
    LogMessageFatal(file, line) << std::string(exprtext);
  }
  return std::forward<T>(t);
}

int64_t MinLogLevelFromEnv();

int64_t MinVLogLevelFromEnv();

}  // namespace internal

// LogSink support adapted from //base/logging.h
//
// `LogSink` is an interface which can be extended to intercept and process
// all log messages. LogSink implementations must be thread-safe. A single
// instance will be called from whichever thread is performing a logging
// operation.
class VeribleLogEntry {
  static absl::LogSeverity AsAbslLogSeverity(int severity) {
    return static_cast<absl::LogSeverity>(severity);
  }

 public:
  explicit VeribleLogEntry(int severity, absl::string_view log_line)
      : severity_(AsAbslLogSeverity(severity)), log_line_(log_line) {}

  absl::LogSeverity log_severity() const { return severity_; }
  std::string ToString() const { return std::string(log_line_); }

 private:
  const absl::LogSeverity severity_;
  const absl::string_view log_line_;
};

class VeribleLogSink {
 public:
  virtual ~VeribleLogSink() = default;

  // `Send` is called synchronously during the log statement.  The logging
  // module guarantees not to call `Send` concurrently on the same log sink.
  // Implementations should be careful not to call`LOG` or `CHECK` or take
  // any locks that might be held by the `LOG` caller, to avoid deadlock.
  //
  // `e` is guaranteed to remain valid until the subsequent call to
  // `WaitTillSent` completes, so implementations may store a pointer to or
  // copy of `e` (e.g. in a thread local variable) for use in `WaitTillSent`.
  virtual void Send(const VeribleLogEntry& entry) = 0;

  // `WaitTillSent` blocks the calling thread (the thread that generated a log
  // message) until the sink has finished processing the log message.
  // `WaitTillSent` is called once per log message, following the call to
  // `Send`.  This may be useful when log messages are buffered or processed
  // asynchronously by an expensive log sink.
  // The default implementation returns immediately.  Like `Send`,
  // implementations should be careful not to call `LOG` or `CHECK or take any
  // locks that might be held by the `LOG` caller, to avoid deadlock.
  virtual void WaitTillSent() {}
};

// Add or remove a `LogSink` as a consumer of logging data.  Thread-safe.
void VeribleAddLogSink(VeribleLogSink* sink);
void VeribleRemoveLogSink(VeribleLogSink* sink);

// Helper for `ABSL_DIE_IF_NULL`.
template <typename T>
ABSL_MUST_USE_RESULT T DieIfNull(const char* file, int line,
                                 const char* exprtext, T&& t) {
  CHECK(t != nullptr) << exprtext;
  return std::forward<T>(t);
}
#ifndef ABSL_DIE_IF_NULL
#define ABSL_DIE_IF_NULL(val) \
  ::verible::DieIfNull(__FILE__, __LINE__, #val, (val))
#endif
}  // namespace verible

#endif  // VERIBLE_COMMON_UTIL_LOGGING_H_