#include <ctype.h>
#include <dlfcn.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <wordexp.h>

static const char *PNAME = "modfetch";

static const uint8_t VERSION_MAJOR = 0;
static const uint8_t VERSION_MINOR = 1;
static const uint8_t VERSION_PATCH = 0;

static const uint8_t MAX_MODULE_NAME_LENGTH = 128;
static const uint8_t MAX_MODULES = 128;
static const uint8_t MAX_MODULE_VARS = 128;

static const char *version_str(void) {
    char *ver;
    if (asprintf(&ver, "%d.%d.%d", VERSION_MAJOR, VERSION_MINOR, VERSION_PATCH) < 0) {
        return NULL;
    }
    return ver;
}

typedef struct {
    // path to the binary of this module
    char *path;
    // name=value strings for each value in config
    char **config;
} Module;

typedef struct {
    size_t module_count;
    Module *modules;
} Config;

void parsing_error(size_t line) {
    fprintf(stderr, "error: failed parsing config at line %zu", line);
    exit(EXIT_FAILURE);
}

char *remove_whitespaces(const char *str) {
    char *tmp = malloc(strlen(str) * sizeof(char));
    size_t i = 0;
    size_t j = 0;
    while (str[i] != '\0') {
        if (isspace(str[i])) {
            ++i;
            continue;
        }
        tmp[j] = str[i];
        ++i;
        ++j;
    }
    tmp[j] = '\0';

    char *ret = malloc(j * sizeof(char));
    strncpy(ret, tmp, j);
    free(tmp);

    return ret;
}

char *resolve_env_vars(const char *str) {
    size_t len = strlen(str);
    char *ret = malloc(4096 * sizeof(char));
    size_t ret_offset = 0;
    bool in_env_var = false;
    char *env_var = malloc(4096 * sizeof(char));
    size_t env_var_offset = 0;

    for (size_t i = 0; i < len; ++i) {
        if (str[i] == '~') {
            char *home = getenv("HOME");
            strcat(ret, home);
            ret_offset += strlen(home);
            continue;
        }
        
        if (str[i] == '$') {
            in_env_var = true;
            continue;
        }

        if (in_env_var && !(isalpha(str[i]) || isdigit(str[i]) || str[i] == '_')) {
            in_env_var = false;

            char *env = getenv(env_var);
            strcat(ret, env);
            ret_offset += strlen(env);
            free(env_var);
            env_var = malloc(4096 * sizeof(char));
            env_var_offset = 0;
        }

        if (in_env_var) {
            env_var[env_var_offset] = str[i];
            ++env_var_offset;
            continue;
        }

        ret[ret_offset] = str[i];
        ++ret_offset;
    }

    free(env_var);

    return ret;
}

Config parse_config(FILE *config_file) {
    size_t len = 0;
    ssize_t read;
    char *line = NULL;
    size_t line_index = 0;
    bool in_config = false; 

    char *current_path = malloc(MAX_MODULE_NAME_LENGTH * sizeof(char));
    Module current_module = {
        .path = malloc(4096 * sizeof(char)),
        .config = malloc(MAX_MODULE_VARS * sizeof(char)),
    };
    size_t config_index = 0;
    
    Config config = {
        .modules = malloc(MAX_MODULES * sizeof(Module)),
        .module_count = 0,
    };
    size_t module_index = 0;

    while ((read = getline(&line, &len, config_file)) != -1) {
        // if config is passed
        if (line[read - 2u] == '{') {
            if (in_config) {
                fclose(config_file);
                parsing_error(line_index);
            }
            in_config = true;
            strncpy(current_path, line, (size_t)read - 2);
            current_module.path = resolve_env_vars(remove_whitespaces(current_path));
            free(current_path);
            current_path = malloc(MAX_MODULE_NAME_LENGTH);
            continue;
        }

        // end of config for current module
        if (line[read - 2u] == '}') {
            if (!in_config) {
                fclose(config_file);
                parsing_error(line_index);
            }
            in_config = false;
            current_module.config[config_index] = NULL;
            config.modules[module_index] = current_module;
            ++module_index;
            current_module.path = malloc(4096 * sizeof(char));
            current_module.config = malloc(MAX_MODULE_VARS * sizeof(char));
            continue;
        }

        if (in_config) {
            current_module.config[config_index] = remove_whitespaces(line);
            ++config_index;
            continue;
        }

        current_module.path = resolve_env_vars(remove_whitespaces(line));
        free(current_module.config);
        current_module.config = malloc(sizeof(void*));
        current_module.config[0] = NULL;
        config.modules[module_index] = current_module;
        ++module_index;
        current_module.path = malloc(4096 * sizeof(char));
        current_module.config = malloc(MAX_MODULE_VARS * sizeof(char));
    }

    config.module_count = module_index;

    return config;
}

int main(int argc, char *argv[]) {

    char *config_path;

    if (asprintf(&config_path, "%s/modfetch.conf", getenv("XDG_CONFIG_HOME")) < 0) {
        fprintf(stderr, "error: failed formatting config path (this shouldn't happen)");
        exit(EXIT_FAILURE);
    }

    for (size_t i = 1; i < (size_t)argc; ++i) {
        if (strcmp(argv[i], "-c") == 0 || strcmp(argv[i], "--config") == 0) {
            if (i == (size_t)argc - 1) {
                fprintf(stderr, "error: no config path passed\n");
                exit(EXIT_FAILURE);
            }

            ++i;
            config_path = argv[i];
            continue;
        }

        if (strcmp(argv[i], "-h") == 0 || strcmp(argv[i], "--help") == 0) {
            fprintf(stderr, "%s: modular fetch [%s]\n", PNAME, version_str());
            fprintf(stderr, "\n");
            fprintf(stderr, "OPTIONS\n");
            fprintf(stderr, "\t-h, --help\t\t\tdisplays this help text\n");
            fprintf(stderr, "\t-c, --config /path/to/config\tchanges config path from the default ($XDG_CONFIG_HOME/%s.conf)\n", PNAME);
            exit(EXIT_SUCCESS);
        }
    }

    FILE *config_file = fopen(config_path, "r");

    if (config_file == NULL) {
        fprintf(stderr, "error: failed to open config at: %s\n", config_path);
        exit(EXIT_FAILURE);
    }

    Config config = parse_config(config_file);

    fclose(config_file);

    for (size_t i = 0; i < config.module_count; ++i) {
        Module current_module = config.modules[i];
        void *handle = dlopen(current_module.path, RTLD_NOW);
        if (handle == NULL) {
            fprintf(stderr, "error: failed opening module %s\n", current_module.path);
            fprintf(stderr, "%s\n", dlerror());
            exit(EXIT_FAILURE);
        }
        dlerror();

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wpedantic"
        uint8_t (*version_major)(void) = dlsym(handle, "version_major");
        uint8_t (*version_minor)(void) = dlsym(handle, "version_minor");
        uint8_t (*version_patch)(void) = dlsym(handle, "version_patch");

        const char *(*module_name)(void) = dlsym(handle, "module_name");
        const char *(*get)(void) = dlsym(handle, "get");
        void (*init)(char**) = dlsym(handle, "init");
#pragma GCC diagnostic pop

        init(current_module.config);

        (void)module_name;
        (void)version_major;
        (void)version_minor;
        (void)version_patch;
        //printf("%s: %d.%d.%d\n", module_name(), version_major(), version_minor(), version_patch());
        printf("%s\n", get());
    }

    return 0;
}