banan-os/userspace/Shell/main.cpp

#include <BAN/ScopeGuard.h>
#include <BAN/String.h>
#include <BAN/Vector.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <termios.h>
#include <unistd.h>

struct termios old_termios, new_termios;

BAN::Vector<BAN::String> parse_command(BAN::StringView command)
{
	enum class State
	{
		Normal,
		SingleQuote,
		DoubleQuote,
	};

	BAN::Vector<BAN::String> result;

	State state = State::Normal;
	BAN::String current;
	for (char c : command)
	{
		switch (state)
		{
			case State::Normal:
				if (c == '\'')
					state = State::SingleQuote;
				else if (c == '"')
					state = State::DoubleQuote;
				else if (!isspace(c))
					MUST(current.push_back(c));
				else
				{
					if (!current.empty())
					{
						MUST(result.push_back(current));
						current.clear();
					}
				}
				break;
			case State::SingleQuote:
				if (c == '\'')
					state = State::Normal;
				else
					MUST(current.push_back(c));
				break;
			case State::DoubleQuote:
				if (c == '"')
					state = State::Normal;
				else
					MUST(current.push_back(c));
				break;
		}
	}

	// FIXME: handle state != State::Normal
	MUST(result.push_back(BAN::move(current)));

	return result;
}

int execute_command(BAN::StringView command)
{
	auto args = parse_command(command);
	if (args.empty())
		return 0;
	
	if (args.front() == "clear"sv)
	{
		fprintf(stdout, "\e[H\e[J");
		fflush(stdout);
		return 0;
	}
	else if (args.front() == "exit"sv)
	{
		exit(0);
	}
	else if (args.front() == "export"sv)
	{
		bool first = false;
		for (const auto& arg : args)
		{
			if (first)
			{
				first = false;
				continue;
			}

			auto split = MUST(arg.sv().split('=', true));
			if (split.size() != 2)
				continue;

			if (setenv(BAN::String(split[0]).data(), BAN::String(split[1]).data(), true) == -1)
			{
				perror("setenv");
				return 1;
			}
		}
	}
	else if (args.front() == "cd"sv)
	{
		if (args.size() > 2)
		{
			printf("cd: too many arguments\n");
			return 1;
		}

		BAN::StringView path;

		if (args.size() == 1)
		{
			if (const char* path_env = getenv("HOME"))
				path = path_env;
			else
				return 0;
		}
		else
			path = args[1];

		if (chdir(path.data()) == -1)
		{
			perror("chdir");
			return 1;
		}
	}
	else
	{
		pid_t pid = fork();
		if (pid == 0)
		{
			BAN::Vector<char*> cmd_args;
			MUST(cmd_args.reserve(args.size() + 1));
			for (const auto& arg : args)
				MUST(cmd_args.push_back((char*)arg.data()));
			MUST(cmd_args.push_back(nullptr));
			execv(cmd_args.front(), cmd_args.data());
			perror("execv");
			exit(1);
		}
		if (pid == -1)
		{
			perror("fork");
			return 1;
		}
		int status;
		if (waitpid(pid, &status, 0) == -1)
			perror("waitpid");
	}

	return 0;
}

int character_length(BAN::StringView prompt)
{
	int length { 0 };
	bool in_escape { false };
	for (char c : prompt)
	{
		if (in_escape)
		{
			if (isalpha(c))
				in_escape = false;
		}
		else
		{
			if (c == '\e')
				in_escape = true;
			else if (((uint8_t)c & 0xC0) != 0x80)
				length++;
		}
	}
	return length;
}

BAN::String get_prompt()
{
	const char* raw_prompt = getenv("PS1");
	if (raw_prompt == nullptr)
		raw_prompt = "\e[32muser@host\e[m:\e[34m\\~\e[m$ ";

	BAN::String prompt;
	for (int i = 0; raw_prompt[i]; i++)
	{
		char ch = raw_prompt[i];
		if (ch == '\\')
		{
			switch (raw_prompt[++i])
			{
			case 'e':
				MUST(prompt.push_back('\e'));
				break;
			case 'n':
				MUST(prompt.push_back('\n'));
				break;
			case '\\':
				MUST(prompt.push_back('\\'));
				break;
			case '~':
			{
				char buffer[256];
				if (getcwd(buffer, sizeof(buffer)) == nullptr)
					strcpy(buffer, strerrorname_np(errno));
				
				const char* home = getenv("HOME");
				size_t home_len = home ? strlen(home) : 0;
				if (home && strncmp(buffer, home, home_len) == 0)
				{
					MUST(prompt.push_back('~'));
					MUST(prompt.append(buffer + home_len));
				}
				else
				{
					MUST(prompt.append(buffer));
				}

				break;
			}
			case '\0':
				MUST(prompt.push_back('\\'));
				break;
			default:
				MUST(prompt.push_back('\\'));
				MUST(prompt.push_back(*raw_prompt));
				break;
			}
		}
		else
		{
			MUST(prompt.push_back(ch));
		}
	}	

	return prompt;
}

int prompt_length()
{
	return character_length(get_prompt());
}

void print_prompt()
{
	auto prompt = get_prompt();
	fprintf(stdout, "%.*s", prompt.size(), prompt.data());
	fflush(stdout);
}

int main(int argc, char** argv)
{
	if (argc >= 1)
		setenv("SHELL", argv[0], true);

	tcgetattr(0, &old_termios);

	new_termios = old_termios;
	new_termios.c_lflag &= ~(ECHO | ICANON);
	tcsetattr(0, TCSANOW, &new_termios);

	BAN::Vector<BAN::String> buffers, history;
	MUST(buffers.emplace_back(""sv));
	size_t index = 0;
	size_t col = 0;

	int waiting_utf8 = 0;

	print_prompt();

	while (true)
	{
		uint8_t ch;
		fread(&ch, 1, sizeof(char), stdin);

		if (waiting_utf8 > 0)
		{
			waiting_utf8--;

			ASSERT((ch & 0xC0) == 0x80);

			fputc(ch, stdout);
			MUST(buffers[index].insert(ch, col++));
			if (waiting_utf8 == 0)
			{
				fprintf(stdout, "\e[s%s\e[u", buffers[index].data() + col);
				fflush(stdout);
			}
			continue;
		}
		else if (ch & 0x80)
		{
			if ((ch & 0xE0) == 0xC0)
				waiting_utf8 = 1;
			else if ((ch & 0xF0) == 0xE0)
				waiting_utf8 = 2;
			else if ((ch & 0xF8) == 0xF0)
				waiting_utf8 = 3;
			else
				ASSERT_NOT_REACHED();
			
			fputc(ch, stdout);
			MUST(buffers[index].insert(ch, col++));
			continue;
		}

		switch (ch)
		{
		case '\e':
			fread(&ch, 1, sizeof(char), stdin);
			if (ch != '[')
				break;
			fread(&ch, 1, sizeof(char), stdin);
			switch (ch)
			{
				case 'A': if (index > 0)					{ index--; col = buffers[index].size(); fprintf(stdout, "\e[%dG%s\e[K", prompt_length() + 1, buffers[index].data()); fflush(stdout); } break;
				case 'B': if (index < buffers.size() - 1)	{ index++; col = buffers[index].size(); fprintf(stdout, "\e[%dG%s\e[K", prompt_length() + 1, buffers[index].data()); fflush(stdout); } break;
				case 'C': if (col < buffers[index].size())	{ col++; while ((buffers[index][col - 1] & 0xC0) == 0x80) col++; fprintf(stdout, "\e[C"); fflush(stdout); } break;
				case 'D': if (col > 0)						{ while ((buffers[index][col - 1] & 0xC0) == 0x80) col--; col--; fprintf(stdout, "\e[D"); fflush(stdout); } break;
			}
			break;
		case '\x0C': // ^L
		{
			int x = prompt_length() + character_length(buffers[index].sv().substring(col)) + 1;
			fprintf(stdout, "\e[H\e[J");
			print_prompt();
			fprintf(stdout, "%s\e[u\e[1;%dH", buffers[index].data(), x);
			fflush(stdout);
			break;
		}
		case '\b':
			if (col > 0)
			{
				while ((buffers[index][col - 1] & 0xC0) == 0x80)
					buffers[index].remove(--col);
				buffers[index].remove(--col);
				fprintf(stdout, "\b\e[s%s \e[u", buffers[index].data() + col);
				fflush(stdout);
			}
			break;
		case '\n':
			fputc('\n', stdout);
			if (!buffers[index].empty())
			{
				tcsetattr(0, TCSANOW, &old_termios);
				execute_command(buffers[index]);
				tcsetattr(0, TCSANOW, &new_termios);
				MUST(history.push_back(buffers[index]));
				buffers = history;
				MUST(buffers.emplace_back(""sv));
			}
			print_prompt();
			index = buffers.size() - 1;
			col = 0;
			break;
		default:
			MUST(buffers[index].insert(ch, col++));
			fprintf(stdout, "%c\e[s%s\e[u", ch, buffers[index].data() + col);
			fflush(stdout);
			break;
		}
	}

	tcsetattr(0, TCSANOW, &old_termios);
	return 0;
}