blob: 21ed7493e449f95d9233c20cdb00496cb0ffc3ab [file] [log] [blame]
// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "pdf/pdf_ink_undo_redo_model.h"
#include <stddef.h>
#include <optional>
#include <set>
#include <vector>
#include "base/check.h"
#include "base/check_op.h"
#include "base/notreached.h"
#include "base/types/strong_alias.h"
#include "third_party/abseil-cpp/absl/types/variant.h"
namespace chrome_pdf {
namespace {
PdfInkUndoRedoModel::DrawCommands& GetModifiableDrawCommands(
PdfInkUndoRedoModel::Commands& commands) {
return absl::get<PdfInkUndoRedoModel::DrawCommands>(commands);
}
PdfInkUndoRedoModel::EraseCommands& GetModifiableEraseCommands(
PdfInkUndoRedoModel::Commands& commands) {
return absl::get<PdfInkUndoRedoModel::EraseCommands>(commands);
}
} // namespace
PdfInkUndoRedoModel::PdfInkUndoRedoModel() = default;
PdfInkUndoRedoModel::~PdfInkUndoRedoModel() = default;
std::optional<PdfInkUndoRedoModel::DiscardedDrawCommands>
PdfInkUndoRedoModel::StartDraw() {
return StartImpl<DrawCommands>();
}
bool PdfInkUndoRedoModel::Draw(size_t id) {
CHECK(!commands_stack_.empty());
if (!IsAtTopOfStackWithGivenCommandType(CommandsType::kDraw)) {
// Can only draw at top of the stack, and the entry there must be for
// drawing.
return false;
}
if (HasIdInDrawCommands(id)) {
return false; // Failed invariant 3.
}
// Invariant 4 holds if invariant 6 holds.
CHECK(!HasIdInEraseCommands(id));
GetModifiableDrawCommands(commands_stack_.back())->insert(id);
return true;
}
bool PdfInkUndoRedoModel::FinishDraw() {
CHECK(!commands_stack_.empty());
if (!IsAtTopOfStackWithGivenCommandType(CommandsType::kDraw)) {
// Can only draw at top of the stack, and the entry there must be for
// drawing.
return false;
}
auto& commands = commands_stack_.back();
if (GetDrawCommands(commands)->empty()) {
commands = absl::monostate(); // Reuse top of stack if empty.
} else {
// Otherwise push new item onto the stack.
++stack_position_;
commands_stack_.push_back(absl::monostate());
}
return true;
}
std::optional<PdfInkUndoRedoModel::DiscardedDrawCommands>
PdfInkUndoRedoModel::StartErase() {
return StartImpl<EraseCommands>();
}
bool PdfInkUndoRedoModel::Erase(size_t id) {
CHECK(!commands_stack_.empty());
if (!IsAtTopOfStackWithGivenCommandType(CommandsType::kErase)) {
// Can only erase at top of the stack, and the entry there must be for
// erasing.
return false;
}
if (!HasIdInDrawCommands(id)) {
return false; // Failed invariant 6.
}
if (HasIdInEraseCommands(id)) {
return false; // Failed invariant 5.
}
GetModifiableEraseCommands(commands_stack_.back())->insert(id);
return true;
}
bool PdfInkUndoRedoModel::FinishErase() {
CHECK(!commands_stack_.empty());
if (!IsAtTopOfStackWithGivenCommandType(CommandsType::kErase)) {
// Can only erase at top of the stack, and the entry there must be for
// erasing.
return false;
}
auto& commands = commands_stack_.back();
if (GetEraseCommands(commands)->empty()) {
commands = absl::monostate(); // Reuse top of stack if empty.
} else {
// Otherwise push new item onto the stack.
++stack_position_;
commands_stack_.push_back(absl::monostate());
}
return true;
}
PdfInkUndoRedoModel::Commands PdfInkUndoRedoModel::Undo() {
CHECK(!commands_stack_.empty());
CHECK_LT(stack_position_, commands_stack_.size());
if (stack_position_ == 0) {
return absl::monostate(); // Already at bottom of stack.
}
// Result is reverse of the recorded commands.
--stack_position_;
const auto& commands = commands_stack_[stack_position_];
switch (GetCommandsType(commands)) {
case CommandsType::kNone: {
NOTREACHED(); // Invariant 2.
}
case CommandsType::kDraw: {
EraseCommands result;
for (size_t id : GetDrawCommands(commands).value()) {
result->insert(id);
}
return result;
}
case CommandsType::kErase: {
DrawCommands result;
for (size_t id : GetEraseCommands(commands).value()) {
result->insert(id);
}
return result;
}
}
NOTREACHED();
}
PdfInkUndoRedoModel::Commands PdfInkUndoRedoModel::Redo() {
CHECK(!commands_stack_.empty());
CHECK_LT(stack_position_, commands_stack_.size());
if (stack_position_ == commands_stack_.size() - 1) {
return absl::monostate(); // Already at top of stack.
}
// Result is the recorded commands as-is.
const auto& commands = commands_stack_[stack_position_];
++stack_position_;
switch (GetCommandsType(commands)) {
case CommandsType::kNone: {
NOTREACHED(); // Invariant 2.
}
case CommandsType::kDraw: {
return GetDrawCommands(commands);
}
case CommandsType::kErase: {
return GetEraseCommands(commands);
}
}
NOTREACHED();
}
// static
PdfInkUndoRedoModel::CommandsType PdfInkUndoRedoModel::GetCommandsType(
const Commands& commands) {
if (absl::holds_alternative<absl::monostate>(commands)) {
return CommandsType::kNone;
}
if (absl::holds_alternative<DrawCommands>(commands)) {
return CommandsType::kDraw;
}
CHECK(absl::holds_alternative<EraseCommands>(commands));
return CommandsType::kErase;
}
// static
const PdfInkUndoRedoModel::DrawCommands& PdfInkUndoRedoModel::GetDrawCommands(
const Commands& commands) {
return absl::get<DrawCommands>(commands);
}
// static
const PdfInkUndoRedoModel::EraseCommands& PdfInkUndoRedoModel::GetEraseCommands(
const Commands& commands) {
return absl::get<EraseCommands>(commands);
}
template <typename T>
std::optional<PdfInkUndoRedoModel::DiscardedDrawCommands>
PdfInkUndoRedoModel::StartImpl() {
CHECK(!commands_stack_.empty());
CHECK_LT(stack_position_, commands_stack_.size());
DiscardedDrawCommands discarded_commands;
auto& commands = commands_stack_[stack_position_];
const bool has_commands = GetCommandsType(commands) != CommandsType::kNone;
if (stack_position_ == commands_stack_.size() - 1) {
if (has_commands) {
// Cannot start when drawing/erasing already started.
return std::nullopt;
}
} else {
CHECK(has_commands); // Invariant 2.
// Record the draw commands to discard.
for (size_t i = stack_position_; i < commands_stack_.size(); ++i) {
if (GetCommandsType(commands_stack_[i]) == CommandsType::kDraw) {
for (size_t id : GetDrawCommands(commands_stack_[i]).value()) {
bool inserted = discarded_commands.insert(id).second;
CHECK(inserted);
}
}
}
// Discard rest of stack.
//
// The vector capacity is never reduced when resizing to smaller size. Thus
// references to `commands_stack_` elements are not invalidated and safe to
// use.
commands_stack_.resize(stack_position_ + 1);
}
// Set the top of the stack to the appropriate command type.
//
// Safe to reuse `commands`, which references an element inside of
// `commands_stack_`. See note above the resize() call regarding safety.
commands = T();
return discarded_commands;
}
bool PdfInkUndoRedoModel::IsAtTopOfStackWithGivenCommandType(
CommandsType type) const {
if (stack_position_ != commands_stack_.size() - 1) {
return false;
}
return GetCommandsType(commands_stack_.back()) == type;
}
bool PdfInkUndoRedoModel::HasIdInDrawCommands(size_t id) const {
for (const auto& commands : commands_stack_) {
if (GetCommandsType(commands) == CommandsType::kDraw &&
GetDrawCommands(commands)->contains(id)) {
return true;
}
}
return false;
}
bool PdfInkUndoRedoModel::HasIdInEraseCommands(size_t id) const {
for (const auto& commands : commands_stack_) {
if (GetCommandsType(commands) == CommandsType::kErase &&
GetEraseCommands(commands)->contains(id)) {
return true;
}
}
return false;
}
} // namespace chrome_pdf