// Copyright 2021 Benjamin Barenblat
//
// 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
//
//     https://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.

// An extremely simple EDSL for describing output to the terminal. It supports
// exactly two instructions: "send some bytes to the terminal" and "sleep". The
// string capability interpreter produces terms in this EDSL, which makes it
// easier to test.

#ifndef EC_GOLDFISHTERM_INTERNAL_EMIT_H_
#define EC_GOLDFISHTERM_INTERNAL_EMIT_H_

#include <stdint.h>

#include <memory>
#include <ostream>
#include <string>
#include <utility>

#include "third_party/abseil/absl/strings/str_cat.h"
#include "third_party/abseil/absl/strings/string_view.h"
#include "third_party/abseil/absl/time/time.h"
#include "third_party/abseil/absl/types/span.h"

namespace goldfishterm_internal {

class EmitTerm {
 public:
  virtual void Emit(std::ostream&) const = 0;

  virtual ~EmitTerm() noexcept = default;
};

class EmitBytes final : public EmitTerm {
 public:
  explicit EmitBytes() noexcept = default;

  explicit EmitBytes(absl::string_view bytes) noexcept : bytes_(bytes) {}

  EmitBytes(const EmitBytes&) = default;
  EmitBytes& operator=(const EmitBytes&) = default;
  EmitBytes(EmitBytes&&) noexcept = default;
  EmitBytes& operator=(EmitBytes&&) noexcept = default;

  bool empty() const noexcept { return bytes_.empty(); }

  void Append(absl::string_view more) noexcept {
    absl::StrAppend(&bytes_, more);
  }

  void Emit(std::ostream&) const override;

  bool operator==(const EmitBytes& other) const noexcept {
    return bytes_ == other.bytes_;
  }

  friend std::ostream& operator<<(std::ostream& out,
                                  const EmitBytes& emit) noexcept {
    return out << "EmitBytes(" << emit.bytes_ << ')';
  }

 private:
  std::string bytes_;
};

class EmitDelay final : public EmitTerm {
 public:
  explicit EmitDelay() noexcept = default;

  explicit EmitDelay(absl::Duration delay) : delay_(std::move(delay)) {}

  EmitDelay(const EmitDelay&) = default;
  EmitDelay& operator=(const EmitDelay&) = default;
  EmitDelay(EmitDelay&&) noexcept = default;
  EmitDelay& operator=(EmitDelay&&) noexcept = default;

  bool zero() const noexcept { return delay_ == absl::ZeroDuration(); }

  void Increase(absl::Duration more) noexcept { delay_ += more; }

  void Emit(std::ostream&) const noexcept override;

  bool operator==(const EmitDelay& other) const noexcept {
    return delay_ == other.delay_;
  }

 private:
  absl::Duration delay_;
};

// Runs an entire program in the emitter EDSL.
void Emit(absl::Span<const std::shared_ptr<const EmitTerm>>, std::ostream&);

}  // namespace goldfishterm_internal

#endif  // EC_GOLDFISHTERM_INTERNAL_EMIT_H_