logmeow/config.cpp

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <cfloat>
#include <sys/stat.h>
#include <string>
#include <memory>

#include "log.h"
#include "misc.h"
#include "config.h"

static FILE* fopen_or_raise(const char* path, const char* mode, bool ignore_enoent) {
    FILE* file = fopen(path, mode);
    if (!file && !(ignore_enoent && errno == ENOENT)) {
        throw_system_error(std::string("fopen(") + quote(path) + ')');
    }
    return file;
}

static void fclose_and_log(FILE* file) {
    if (!fclose(file)) {
        return;
    }
    log(std::string("Failed to close a file: fclose(): ") + strerror(errno));
}

static bool write(const std::string& ptr, FILE* file) {
    return fwrite(ptr.data(), sizeof(char), ptr.size(), file) == ptr.size() * sizeof(char);
}
static bool write(const char* ptr, FILE* file) {
    return fwrite(ptr, 1, strlen(ptr), file) == strlen(ptr);
}

static inline float to_float(const char* str) {
    char* endptr;

    while (isspace(str[0])) {
        str++;
    }
    if (str[0] == '\0') {
        throw std::invalid_argument("float string is empty");
    }

    errno = 0;
    float res = strtof(str, &endptr);
    if (res == HUGE_VALF && errno == ERANGE) {
        throw std::overflow_error(std::string(str) + " is bigger than HUGE_VALF");
    } else if (res == FLT_MIN && errno == ERANGE) {
        throw std::underflow_error(std::string(str) + " is smaller than FLT_MIN");
    } else if (endptr[0] != '\0') {
        throw std::invalid_argument(std::string(str) + " has trailing text");
    }
    return res;
}

static bool validate_font_size_or_log(float size) {
    if (size <= 0.0f) {
        log(std::string("Font size ") + std::to_string(size) + " is lower or equal to 0");
        return false;
    } else if (std::isnan(size)) {
        log(std::string("Font size ") + std::to_string(size) + " is NaN");
        return false;
    } else if (std::isinf(size)) {
        log(std::string("Font size ") + std::to_string(size) + " is infinity or negative infinity");
        return false;
    }
    return true;
}


std::string get_config_folder() {
    const char* path;

    path = getenv("XDG_CONFIG_HOME");
    if (path) {
        return std::string(path) + "/logmeow";
    }
    path = getenv("HOME");
    if (path) {
        return std::string(path) + "/.config/logmeow";
    }

    throw std::runtime_error("cannot find suitable config folder, please set XDG_CONFIG_HOME or HOME");
}

std::string get_config_file_path() {
    return get_config_folder() + "/config";
}

// tries to create a directory with an empty string if it's just "/" but who cares
void create_config_folders_if_necessary() {
    std::string full_path = get_config_folder();
    std::string path;
    size_t pos = 0;

    while (pos != std::string::npos) {
        pos = full_path.find('/', pos);
        if (pos != std::string::npos) {
            pos++;
        }
        path = full_path.substr(0, pos);
        if (!mkdir(path.c_str(), 0600)) {
            continue;
        }
        if (errno == EEXIST) {
            continue;
        }
        throw_system_error(std::string("mkdir(") + quote(path) + ')');
    }
}


static inline void parse_config_line(Config& config, char* line) {
    if (strncmp(line, "logcat_command=", 15 * sizeof(char)) == 0) {
        config.logcat_command = &line[15];
    } else if (strncmp(line, "normal_font_size=", 17 * sizeof(char)) == 0) {
        float size = to_float(&line[17]);
        if (validate_font_size_or_log(size)) {
            config.normal_font_size = size;
        }
    } else if (strncmp(line, "monospace_font_size=", 20 * sizeof(char)) == 0) {
        float size = to_float(&line[20]);
        if (validate_font_size_or_log(size)) {
            config.monospace_font_size = size;
        }
    } else if (line[0] != '\0') {
        throw std::invalid_argument(std::string("unknown config line: ") + line);
    }
}

static inline Config load_config(FILE* file) {
    size_t line_capacity_size = 128 * sizeof(char);
    char* line = static_cast<char*>(malloc(line_capacity_size));
    if (line == nullptr) {
        throw std::bad_alloc();
    }
    Config config;

    while (true) {
        errno = 0;
        if (getline(&line, &line_capacity_size, file) < 0) {
            // https://stackoverflow.com/questions/30569981/does-free-set-errno
            int errsv = errno;
            free(line);
            if (errsv) {
                throw_system_error(errsv, "getline()");
            }
            break;
        }
        if (line_capacity_size == 0 || line[0] == '\0' || line[0] == '#') {
            continue;
        }
        if (char* newline = strchr(line, '\n')) {
            *newline = '\0';
        }

        try {
            parse_config_line(config, line);
        } catch (const std::exception& e) {
            free(line);
            throw;
        }
    }

    return config;
}

Config load_config() {
    std::string config_file_path = get_config_file_path();
    std::unique_ptr<FILE, decltype(&fclose_and_log)> config_file(fopen_or_raise(config_file_path.c_str(), "r", true), fclose_and_log);

    if (!config_file) {
        return Config();
    }

    return load_config(config_file.get());
}


static inline void write_config(FILE* file, const Config& config) {
    if (!write("# This is an auto-generated file, modifications will be lost\n"
               "# This is a poor man's config file \"format\", there are only three legal lines:\n"
               "#     # a comment, only available at the start of a line\n"
               "#     (an empty line, no whitespace)\n"
               "#     key=value pairs, no spaces around the delimiter, and no unknown keys\n\n", file)) {
        throw std::runtime_error("Failed to write info comment");
    }
    if (!write("logcat_command=", file)) {
        throw std::runtime_error("Failed to write logcat command key");
    }
    if (!write(config.logcat_command, file)) {
        throw std::runtime_error("Failed to write logcat command value");
    }

    if (!write("\nnormal_font_size=", file)) {
        throw std::runtime_error("Failed to write normal font size key");
    }
    if (!write(std::to_string(config.normal_font_size), file)) {
        throw std::runtime_error("Failed to write normal font size value");
    }
    if (!write("\nmonospace_font_size=", file)) {
        throw std::runtime_error("Failed to write monospace font size key");
    }
    if (!write(std::to_string(config.monospace_font_size), file)) {
        throw std::runtime_error("Failed to write monospace font size value");
    }
}

void write_config(const Config& config) {
    std::string config_file_path = get_config_file_path();
    std::string tmp_config_file_path = config_file_path + ".tmp";

    std::unique_ptr<FILE, decltype(&fclose_and_log)> config_file(fopen_or_raise(tmp_config_file_path.c_str(), "w", false), fclose_and_log);
    write_config(config_file.get(), config);
    config_file.reset();

    if (!rename(tmp_config_file_path.c_str(), config_file_path.c_str())) {
        return;
    }
    throw_system_error(std::string("rename(") + quote(tmp_config_file_path) + ", " + quote(config_file_path) + ')');
}