clean up path logic a bit

10 files changed, 237 insertions, 72 deletions

diff --git a/lib/nes/app/file-browser.hh b/lib/nes/app/file-browser.hh
index b766f74..67be794 100644
--- a/lib/nes/app/file-browser.hh
+++ b/lib/nes/app/file-browser.hh
@@ -46,8 +46,8 @@ namespace nes::app
 		auto operator=(file_browser&&) -> file_browser& = delete;
 
 		virtual auto get_path() const -> path_view = 0;
-		virtual auto read_item_count() -> u32 = 0;
-		virtual auto read_items(u32 offset, item* buffer, u32 buffer_size) -> u32 = 0;
+		virtual auto seek(u32) -> void = 0;
+		virtual auto read_next(item* out_item) -> bool = 0;
 		virtual auto navigate_up() -> void = 0;
 		virtual auto navigate(std::string_view) -> void = 0;
 		virtual auto load(std::string_view, u8* buffer, u32 buffer_size) -> u32 = 0;
diff --git a/lib/nes/app/graphics/renderer.hh b/lib/nes/app/graphics/renderer.hh
index 5b9ec48..cfc1889 100644
--- a/lib/nes/app/graphics/renderer.hh
+++ b/lib/nes/app/graphics/renderer.hh
@@ -56,10 +56,10 @@ namespace nes::app
 			i32 const x, i32 const y, color const c, text_attributes const attrs, std::string_view const fmt,
 			Args... args) -> u32
 		{
-			char buffer[width];
-			auto const str = string_builder{ buffer, sizeof(buffer) }.append_format(fmt, args...).get_result();
-			render_text(x, y, str, c, attrs);
-			return static_cast<u32>(str.length());
+			string_buffer<width> buffer{};
+			buffer.append_format(fmt, args...);
+			render_text(x, y, buffer.get_result(), c, attrs);
+			return static_cast<u32>(buffer.get_result().length());
 		}
 
 		template<typename... Args>
diff --git a/lib/nes/app/ui/screen-browser.cc b/lib/nes/app/ui/screen-browser.cc
index daca18e..6a18d3c 100644
--- a/lib/nes/app/ui/screen-browser.cc
+++ b/lib/nes/app/ui/screen-browser.cc
@@ -3,7 +3,6 @@
 #include "nes/app/graphics/color.hh"
 #include "nes/app/graphics/tiles/icons.hh"
 #include "nes/app/input/input-device-keyboard.hh"
-#include "nes/common/string-builder.hh"
 #include "nes/common/path-view.hh"
 
 namespace nes::app
@@ -23,23 +22,37 @@ namespace nes::app
 			.set_max_width(width - 2));
 	}
 
-	auto screen_browser::selection_impl::load_page(item (&items)[8], u32 const page) -> u32
+	auto screen_browser::selection_impl::load_page(item (&items)[page_size], u32 const page) -> u32
 	{
-		auto offset = u32{ 0 };
-		if (page == 0 && file_browser_.get_path().get_component_count() > 0)
+		auto count = u32{ 0 };
+		auto position = page * page_size;
+		if (!file_browser_.get_path().is_empty())
 		{
-			items[0].is_parent = true;
-			items[0].data = file_browser::item{ file_browser::item_type::directory, "[Parent Directory]" };
-			offset = 1;
+			if (page == 0)
+			{
+				items[count].is_parent = true;
+				items[count].data = file_browser::item{ file_browser::item_type::directory, "[Parent Directory]" };
+				count += 1;
+			}
+			else
+			{
+				// First page has been missing an item, offset by one.
+				position -= 1;
+			}
 		}
-		file_browser::item buffer[8];
-		auto const count = file_browser_.read_items(page * 8, buffer, 8 - offset);
-		for (auto i = u32{ 0 }; i < count; ++i)
+
+		file_browser_.seek(position);
+		while (count < page_size)
 		{
-			items[i + offset].is_parent = false;
-			items[i + offset].data = buffer[i];
+			auto item = file_browser::item{};
+			if (!file_browser_.read_next(&item)) { break; }
+
+			items[count].is_parent = false;
+			items[count].data = item;
+			count += 1;
 		}
-		return count + offset;
+
+		return count;
 	}
 
 	screen_browser::screen_browser(input_device_keyboard& keyboard, file_browser& file_browser)
@@ -47,7 +60,7 @@ namespace nes::app
 		, file_browser_{ file_browser }
 		, selection_{ file_browser }
 	{
-		selection_.set_page_count(std::max(u32{ 1 }, (file_browser_.read_item_count() + 7) / 8));
+		refresh();
 	}
 
 	auto screen_browser::render(renderer& renderer) -> void
@@ -59,16 +72,9 @@ namespace nes::app
 			30, 1, color::foreground_secondary, text_attributes{}.set_alignment(text_alignment::right),
 			"Page {}/{}", selection_.get_current_page() + 1, selection_.get_page_count());
 
-		char path_buffer[32];
-		auto path_builder = string_builder{ path_buffer, sizeof(path_buffer) };
-		for (auto const component : file_browser_.get_path())
-		{
-			path_builder.append_format("> {} ", component);
-		}
-		path_builder.append_string(">");
 		renderer.render_text(
-			2, 1, path_builder.get_result(), color::foreground_primary,
-			text_attributes{}.set_max_width(26 - page_length).set_ellipsize_mode(ellipsize_mode::end));
+			2, 1, file_browser_.get_path().get_path(), color::foreground_primary,
+			text_attributes{}.set_max_width(26 - page_length).set_ellipsize_mode(ellipsize_mode::middle));
 
 		selection_.render(renderer);
 	}
@@ -91,17 +97,27 @@ namespace nes::app
 			}
 			else if (event == input_event::key_down(key::backspace))
 			{
-				return action::go_to_title();
+				if (navigation_steps_ > 0)
+				{
+					file_browser_.navigate_up();
+					refresh();
+					navigation_steps_ -= 1;
+				}
+				else
+				{
+					return action::go_to_title();
+				}
 			}
 			else if (event == input_event::key_down(key::enter))
 			{
-				auto selected = selection_.get_selected();
+				auto const selected = selection_.get_selected();
 				if (selected)
 				{
 					if (selected->is_parent)
 					{
 						file_browser_.navigate_up();
-						selection_.set_page_count(std::max(u32{ 1 }, (file_browser_.read_item_count() + 7) / 8));
+						refresh();
+						if (navigation_steps_ > 0) { navigation_steps_ -= 1; }
 					}
 					else
 					{
@@ -109,7 +125,8 @@ namespace nes::app
 						{
 							case file_browser::item_type::directory:
 								file_browser_.navigate(selected->data.get_name());
-								selection_.set_page_count(std::max(u32{ 1 }, (file_browser_.read_item_count() + 7) / 8));
+								refresh();
+								navigation_steps_ += 1;
 								break;
 							case file_browser::item_type::file:
 								return action::launch_game(selected->data.get_name());
@@ -121,4 +138,15 @@ namespace nes::app
 
 		return action{};
 	}
+
+	auto screen_browser::refresh() -> void
+	{
+		file_browser_.seek(0);
+		auto count = u32{ 0 };
+		while (file_browser_.read_next(nullptr)) { count += 1; }
+		// Round up to get page count.
+		auto const page_count = (count + (page_size - 1)) / page_size;
+		// Always show at least one page.
+		selection_.set_page_count(std::max(u32{ 1 }, page_count));
+	}
 } // namespace nes::app
\ No newline at end of file
diff --git a/lib/nes/app/ui/screen-browser.hh b/lib/nes/app/ui/screen-browser.hh
index 7a711c5..3870f02 100644
--- a/lib/nes/app/ui/screen-browser.hh
+++ b/lib/nes/app/ui/screen-browser.hh
@@ -11,13 +11,15 @@ namespace nes::app
 	/// An interface which allows the user to browse the filesystem for a game.
 	class screen_browser final : public screen
 	{
+		static constexpr auto page_size = u32{ 8 };
+
 		struct item
 		{
 			bool is_parent{ false };
 			file_browser::item data{ file_browser::item_type::directory, "" };
 		};
 
-		class selection_impl final : public selection<item, 8>
+		class selection_impl final : public selection<item, page_size>
 		{
 			file_browser& file_browser_;
 
@@ -30,17 +32,21 @@ namespace nes::app
 
 		protected:
 			auto render_item(renderer&, item const&, i32 x, i32 y, u32 width, color) const -> void override;
-			auto load_page(item(&)[8], u32 page) -> u32 override;
+			auto load_page(item(&)[page_size], u32 page) -> u32 override;
 		};
 
 		input_device_keyboard& keyboard_;
 		file_browser& file_browser_;
 		selection_impl selection_;
+		u32 navigation_steps_{ 0 };
 
 	public:
 		explicit screen_browser(input_device_keyboard&, file_browser&);
 
 		auto render(renderer&) -> void override;
 		auto process_events() -> action override;
+
+	private:
+		auto refresh() -> void;
 	};
 } // namespace nes::app
\ No newline at end of file
diff --git a/lib/nes/common/CMakeLists.txt b/lib/nes/common/CMakeLists.txt
index 11143d7..f0ee288 100644
--- a/lib/nes/common/CMakeLists.txt
+++ b/lib/nes/common/CMakeLists.txt
@@ -8,4 +8,8 @@ target_sources(
 		box.hh
 		display.hh
 		string-builder.hh
-		string-builder.cc)
\ No newline at end of file
+		string-builder.cc
+		path-view.hh
+		path-view.cc
+		path-builder.hh
+		path-builder.cc)
\ No newline at end of file
diff --git a/lib/nes/common/path-builder.cc b/lib/nes/common/path-builder.cc
new file mode 100644
index 0000000..67190dc
--- /dev/null
+++ b/lib/nes/common/path-builder.cc
@@ -0,0 +1,47 @@
+#include "nes/common/path-builder.hh"
+
+namespace nes
+{
+	path_builder::path_builder(char* buffer, u32 const buffer_length)
+		: buffer_{ buffer }
+		, buffer_length_{ buffer_length }
+	{
+		// Initialize the path to "/" if possible.
+		if (buffer_length > 0) { buffer_[actual_length_++] = '/'; }
+	}
+
+	auto path_builder::push(std::string_view component) -> bool
+	{
+		// Trim leading and trailing slashes
+		while (!component.empty() && component[0] == '/') { component = component.substr(1); }
+		while (!component.empty() && component[component.length() - 1] == '/') { component = component.substr(0, component.length() - 1); }
+		if (component.empty() || std::find(component.begin(), component.end(), '/') != component.end()) { return false; }
+
+		// Check if there is enough remaining capacity for "/<component>"
+		auto const add_leading_slash = actual_length_ == 0 || buffer_[actual_length_ - 1] != '/';
+		auto const length = component.length() + (add_leading_slash ? 1 : 0);
+		if (actual_length_ + length > buffer_length_) { return false; }
+
+		// Append "/<component>"
+		if (add_leading_slash) { buffer_[actual_length_++] = '/'; }
+		for (auto i = u32{ 0 }; i < component.length(); ++i) { buffer_[actual_length_++] = component[i]; }
+
+		return true;
+	}
+
+	auto path_builder::pop() -> bool
+	{
+		if (actual_length_ == 0 || buffer_[actual_length_ - 1] == '/') { return false; }
+
+		// Find the start of the last component.
+		auto last_start = actual_length_ - 1;
+		while (last_start > 0 && buffer_[last_start] != '/') { last_start -= 1; }
+
+		// Drop the slash if we are not at the root.
+		if (last_start == 0) { last_start += 1; }
+
+		// Drop everything including the trailing slash.
+		actual_length_ = last_start;
+		return true;
+	}
+} // namespace nes
\ No newline at end of file
diff --git a/lib/nes/common/path-builder.hh b/lib/nes/common/path-builder.hh
new file mode 100644
index 0000000..727d18c
--- /dev/null
+++ b/lib/nes/common/path-builder.hh
@@ -0,0 +1,38 @@
+#pragma once
+
+#include "nes/common/types.hh"
+#include "nes/common/path-view.hh"
+#include <string_view>
+
+namespace nes
+{
+	/// A mutable path with a fixed-length buffer.
+	class path_builder
+	{
+		char* buffer_{ nullptr };
+		u32 buffer_length_{ 0 };
+		u32 actual_length_{ 0 };
+
+	public:
+		explicit path_builder(char* buffer, u32 buffer_length);
+
+		auto get_components() const -> path_view { return path_view{ get_path() }; }
+		auto get_path() const -> std::string_view { return std::string_view{ buffer_, actual_length_ }; }
+
+		auto push(std::string_view) -> bool;
+		auto pop() -> bool;
+	};
+
+	/// A path builder with a buffer embedded into it.
+	template<u32 Capacity>
+	class path_buffer : public path_builder
+	{
+		char buffer_[Capacity];
+
+	public:
+		explicit path_buffer()
+			: path_builder{ buffer_, Capacity }
+		{
+		}
+	};
+} // namespace nes
\ No newline at end of file
diff --git a/lib/nes/common/path-view.cc b/lib/nes/common/path-view.cc
new file mode 100644
index 0000000..47f198b
--- /dev/null
+++ b/lib/nes/common/path-view.cc
@@ -0,0 +1,49 @@
+#include "nes/common/path-view.hh"
+
+namespace nes
+{
+	auto path_view::iterator::operator*() const -> std::string_view
+	{
+		return current_ ? std::string_view{ current_, component_length_ } : "";
+	}
+
+	auto path_view::iterator::operator++() -> iterator&
+	{
+		// Move forward to next component
+		current_ += component_length_;
+		remaining_ -= component_length_;
+
+		// Skip over '/'.
+		while (remaining_ > 0 && *current_ == '/')
+		{
+			current_ += 1;
+			remaining_ -= 1;
+		}
+
+		// Scan until end of component to find its length.
+		component_length_ = 0;
+		while (component_length_ < remaining_ && current_[component_length_] != '/')
+		{
+			component_length_ += 1;
+		}
+
+		return *this;
+	}
+
+	auto path_view::iterator::operator++(int) -> iterator
+	{
+		auto const res = *this;
+		++*this;
+		return res;
+	}
+
+	auto path_view::begin() const -> iterator
+	{
+		return ++iterator{ path_.data(), 0, static_cast<u32>(path_.size()) };
+	}
+
+	auto path_view::end() const -> iterator
+	{
+		return iterator{ path_.data() + path_.size(), 0, 0 };
+	}
+} // namespace nes
\ No newline at end of file
diff --git a/lib/nes/common/path-view.hh b/lib/nes/common/path-view.hh
index 3d670bf..7741060 100644
--- a/lib/nes/common/path-view.hh
+++ b/lib/nes/common/path-view.hh
@@ -5,13 +5,10 @@
 
 namespace nes
 {
-	/// Non-owning copy of a path, consisting of multiple path components stored as string views.
-	///
-	/// This is similar in spirit to a string_view, but for collections of string_views instead of characters.
+	/// Non-owning copy of a path, useful for iterating over its components.
 	class path_view
 	{
-		std::string_view const* components_{ nullptr };
-		u32 component_count_{ 0 };
+		std::string_view path_;
 
 	public:
 		/// An iterator for the path components.
@@ -19,54 +16,37 @@ namespace nes
 		{
 			friend path_view;
 
-			std::string_view const* current_{ nullptr };
-			u32 remaining_{ 0 };
+			char const* current_{ nullptr }; // Start of the current component
+			u32 component_length_{ 0 }; // Length of the current component
+			u32 remaining_{ 0 }; // Number of characters remaining in the buffer, including the current component.
 
 		public:
 			auto operator==(iterator const& other) -> bool { return current_ == other.current_; }
 			auto operator!=(iterator const& other) -> bool { return current_ != other.current_; }
 
-			auto operator*() const -> std::string_view { return current_ ? *current_ : ""; }
-
-			auto operator++() -> iterator&
-			{
-				if (remaining_ > 0)
-				{
-					current_ += 1;
-					remaining_ -= 1;
-				}
-				return *this;
-			}
-
-			auto operator++(int) -> iterator
-			{
-				auto res = *this;
-				++*this;
-				return res;
-			}
+			auto operator*() const -> std::string_view;
+			auto operator++() -> iterator&;
+			auto operator++(int) -> iterator;
 
 		private:
-			explicit iterator() = default;
-			explicit iterator(std::string_view const* current, u32 const remaining)
+			explicit iterator(char const* current, u32 const component_length, u32 const remaining)
 				: current_{ current }
+				, component_length_{ component_length }
 				, remaining_{ remaining }
 			{
 			}
 		};
 
 		explicit path_view() = default;
-
-		explicit path_view(std::string_view const* components, u32 const component_count)
-			: components_{ components }
-			, component_count_{ component_count }
+		explicit path_view(std::string_view const path)
+			: path_{ path }
 		{
 		}
 
-		auto get_components() const -> std::string_view const* { return components_; }
-		auto get_component_count() const -> u32 { return component_count_; }
-		auto get_component(u32 const index) const -> std::string_view { return components_[index]; }
+		auto get_path() const -> std::string_view { return path_; }
 
-		auto begin() const -> iterator { return iterator{ components_, component_count_ }; }
-		auto end() const -> iterator { return iterator{ components_ + component_count_, 0 }; }
+		auto begin() const -> iterator;
+		auto end() const -> iterator;
+		auto is_empty() const -> bool { return begin() == end(); }
 	};
 } // namespace nes::app
\ No newline at end of file
diff --git a/lib/nes/common/string-builder.hh b/lib/nes/common/string-builder.hh
index fda85a4..e0bc673 100644
--- a/lib/nes/common/string-builder.hh
+++ b/lib/nes/common/string-builder.hh
@@ -95,4 +95,17 @@ namespace nes
 		auto append_format(std::string_view fmt, format_arg const* args, u32 arg_count) -> string_builder&;
 		auto append_format_arg(format_arg, std::string_view params) -> string_builder&;
 	};
+
+	/// A string builder with a buffer embedded into it.
+	template<u32 Capacity>
+	class string_buffer : public string_builder
+	{
+		char buffer_[Capacity];
+
+	public:
+		explicit string_buffer()
+			: string_builder{ buffer_, Capacity }
+		{
+		}
+	};
 } // namespace nes
\ No newline at end of file