// 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.

// Parses and interprets terminfo string capabilities. These are written in a
// simple stack-based programming language whose semantics are documented in
// terminfo(5).

#ifndef EC_GOLDFISHTERM_INTERNAL_STRING_CAPABILITY_H_
#define EC_GOLDFISHTERM_INTERNAL_STRING_CAPABILITY_H_

#include <memory>
#include <string>
#include <utility>
#include <vector>

#include "goldfishterm/internal/emit.h"
#include "goldfishterm/terminfo.h"
#include "third_party/abseil/absl/types/optional.h"
#include "third_party/abseil/absl/types/variant.h"

namespace goldfishterm_internal {

using StringCapabilityParameter = absl::variant<int, std::string>;

struct InterpretStringCapabilityInput {
  std::string capability;
  std::vector<StringCapabilityParameter> parameters;

  // The number of lines affected by this operation.
  int lines_affected;

  // The minimum baud rate at which padding should be expanded.
  int padding_baud_rate;

  // The padding character, or absl::nullopt if the terminal doesn't support
  // padding.
  absl::optional<char> pad_char;

  // True iff the terminal supports XON/XOFF handshaking.
  bool has_xon_xoff;

  // The baud rate of the terminal.
  int baud;

  // The number of extra bits sent per character. For a terminal emulator, this
  // is generally 0; for an RS-232 line, it's generally 2 or 3 (one start bit,
  // one stop bit, and possibly one parity bit).
  int extra_bits_per_character;

  // Constructs an InterpretStringCapabilityInput with fail-safe defaults.
  explicit InterpretStringCapabilityInput() noexcept
      : lines_affected(1),
        padding_baud_rate(0),
        pad_char('\0'),
        has_xon_xoff(false),
        baud(9600),
        extra_bits_per_character(0) {}

  // Constructs an InterpretStringCapabilityInput from a terminfo entry.
  explicit InterpretStringCapabilityInput(
      const goldfishterm::TerminfoEntry& terminfo, std::string capability_,
      std::vector<StringCapabilityParameter> parameters_, int baud_,
      int lines_affected_) noexcept
      : capability(std::move(capability_)),
        parameters(std::move(parameters_)),
        lines_affected(lines_affected_),
        padding_baud_rate(
            terminfo.get(goldfishterm::NumericCapability::kPaddingBaudRate)
                .value_or(0)),
        pad_char(terminfo.get(goldfishterm::StringCapability::kCharPadding)
                     .value_or(std::string(1, '\0'))[0]),
        has_xon_xoff(terminfo.get(goldfishterm::BooleanCapability::kXonXoff)),
        baud(baud_),
        extra_bits_per_character(0) {}
};

struct InterpretStringCapabilityResult {
  // Terms in the emitter EDSL (see emit.h).
  std::vector<std::shared_ptr<const EmitTerm>> terms;

  // The expected cost of emitting these terms. This is a unitless, arbitrarily
  // scaled real number; it will be at least 0, but you should not rely on any
  // absolute semantics.
  float cost;
};

// Interprets a terminfo string capability, expanding parameters and inserting
// padding and delays as appropriate. Throws std::runtime_error if parsing or
// interpretation fails.
InterpretStringCapabilityResult InterpretStringCapability(
    const InterpretStringCapabilityInput&);

}  // namespace goldfishterm_internal

#endif  // EC_GOLDFISHTERM_INTERNAL_STRING_CAPABILITY_H_