#include <stdexcept>
#include <cstring>
#include <errno.h>
#include <unistd.h>
#include <signal.h>
#include <sys/wait.h>
#include "command.h"


std::pair<int, std::string> readCommand(const std::vector<std::string> &args) {
	int pipefd[2];
	if (pipe(pipefd) < 0) {
		throw std::runtime_error("readCommand: pipe: " + std::string{strerror(errno)});
	}

	pid_t pid = fork();
	if (pid < 0) {
		throw std::runtime_error("readCommand: fork: " + std::string{strerror(errno)});
	}

	if (pid == 0) {
		close(STDOUT_FILENO);
		dup2(pipefd[1], STDOUT_FILENO);
		close(pipefd[0]);
		close(pipefd[1]);

		std::vector<char*> argv(args.size() + 1);
		for (size_t i = 0; i < args.size(); i++) {
			argv[i] = new char[args[i].size() + 1];
			memcpy(argv[i], args[i].data(), args[i].size() + 1);
		}
		argv[args.size()] = nullptr;

		execvp(argv[0], argv.data());
		perror("execvp");
		exit(255);
	}

	close(pipefd[1]);

	std::string output;
	while (true) {
		size_t base = output.size();
		output.resize(base + 4096);
		ssize_t nr = read(pipefd[0], output.data() + base, 4096);
		if (nr < 0) {
			if (errno == EINTR) {
				output.resize(base);
				continue;
			}
			kill(pid, SIGTERM);
			throw std::runtime_error("readCommand: read: " + std::string{strerror(errno)});
		}
		output.resize(base + nr);
		if (nr == 0) break;
	}

	while (true) {
		int status;
		pid_t wpid = waitpid(pid, &status, 0);
		if (wpid < 0) {
			if (errno == EINTR) continue;
			kill(pid, SIGTERM);
			throw std::runtime_error("readCommand: wait: " + std::string{strerror(errno)});
		}
		if (WIFEXITED(status)) {
			return std::make_pair(WEXITSTATUS(status), output);
		}
	}
}

std::string runCommand(const std::vector<std::string> &args) {
	auto result = readCommand(args);
	if (result.first != 0) {
		std::string cmdline;
		for (const std::string &a : args) cmdline += " " + a;
		throw std::runtime_error(
			"Command exited with exit code " + std::to_string(result.first) + ":" + cmdline
		);
	}
	return result.second;
}