#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>

//#define MAX_DATA 512
//#define MAX_ROWS 100

struct Address {
    int id;
    int set;
    char *name;
    char *email;
};

struct Database {
    struct Address *rows;
    int MAX_DATA;
    int MAX_ROWS;
};

struct Connection {
    FILE *file;
    struct Database *db;
};

void die(const char *message)
{
    if(errno) {
        perror(message);
    } else {
        printf("ERROR: %s\n", message);
    }

    exit(1);
}

void Address_print(struct Address *addr)
{
    printf("%d %s %s\n",
            addr->id, addr->name, addr->email);
}

void Database_load(struct Connection *conn)
{
    int rc = fread(conn->db, sizeof(struct Database), 1, conn->file);
    if(rc != 1) die("Failed to load database. First round.");

//    printf("Max data : %d, max rows: %d\n", conn->db->MAX_DATA, conn->db->MAX_ROWS);
    rewind(conn->file);
    conn->db->rows = malloc(sizeof(struct Address) * conn->db->MAX_ROWS);
    if(conn->db->rows == NULL) die("Failed to allocate memory for rows");
    int rc1 = fread(conn->db, sizeof(struct Database), 1, conn->file);
    if(rc1 != 1) die("Failed to load database. Second round.");
}

struct Connection *Database_open(const char *filename, char mode)
{
    struct Connection *conn = malloc(sizeof(struct Connection));
    if(!conn) die("Memory error");

    conn->db = malloc(sizeof(struct Database));
    if(!conn->db) die("Memory error");

    if(mode == 'c') {
        conn->file = fopen(filename, "w");
    } else {
        conn->file = fopen(filename, "r+");

        if(conn->file) {
            Database_load(conn);
        }
    }

    if(!conn->file) die("Failed to open the file");

    return conn;
}

void Database_close(struct Connection *conn)
{
    if(conn) {
        if(conn->file) fclose(conn->file);
        if(conn->db) free(conn->db);
        free(conn);
    }
}

void Database_write(struct Connection *conn)
{
    rewind(conn->file);

    int rc = fwrite(conn->db, sizeof(struct Database), 1, conn->file);
    if(rc != 1) die("Failed to write database.");

    rc = fflush(conn->file);
    if(rc == -1) die("Cannot flush database.");
}

void Database_create(struct Connection *conn, int MAX_DATA, int MAX_ROWS)
{
    int i = 0;
    conn->db->MAX_DATA = MAX_DATA;
    conn->db->MAX_ROWS = MAX_ROWS;
    conn->db->rows = malloc(sizeof(struct Address) * MAX_ROWS);
    for(i = 0; i < MAX_ROWS; i++) {
        struct Address addr = {.id = i, .set = 0};
        conn->db->rows[i] = addr;
    struct Address *addr1 = &conn->db->rows[i];
    printf("set = %d\n", addr1->set);
    }
}

void Database_set(struct Connection *conn, int id, const char *name, const char *email)
{
    struct Address *addr = &conn->db->rows[id];
    int MAX_DATA = conn->db->MAX_DATA;
    if(addr->set) die("Already set, delete it first");

    addr->set = 1;
    addr->name = malloc(sizeof(char) * MAX_DATA);
    addr->email = malloc(sizeof(char) * MAX_DATA);
    // WARNING: bug, read the "How To Break It" and fix this
    char *res = strncpy(addr->name, name, MAX_DATA);
    // demonstrate the strncpy bug
    if(!res) die("Name copy failed");

    res = strncpy(addr->email, email, MAX_DATA);
    if(!res) die("Email copy failed");
}

void Database_get(struct Connection *conn, int id)
{
    struct Address *addr = &conn->db->rows[id];

    if(addr->set) {
        Address_print(addr);
    } else {
        die("ID is not set");
    }
}

void Database_delete(struct Connection *conn, int id)
{
    struct Address addr = {.id = id, .set = 0};
    conn->db->rows[id] = addr;
}

void Database_list(struct Connection *conn)
{
    int i = 0;
    struct Database *db = conn->db;
    int MAX_ROWS = conn->db->MAX_ROWS;
    for(i = 0; i < MAX_ROWS; i++) {
        struct Address *cur = &db->rows[i];

        if(cur->set) {
            Address_print(cur);
        }
    }
}

int main(int argc, char *argv[])
{
    if(argc < 3) die("USAGE: ex17 <dbfile> <action> [action params]");

    char *filename = argv[1];
    char action = argv[2][0];
    struct Connection *conn = Database_open(filename, action);
    int id = 0;

//    if(argc > 3) id = atoi(argv[3]);
 //   if(id >= MAX_ROWS) die("There's not that many records.");

    switch(action) {
        case 'c':
        if(argc < 5) die("Required: MAX_DATA, MAX_ROWS");
            Database_create(conn, atoi(argv[3]), atoi(argv[4]));
            Database_write(conn);
            break;

        case 'g':
            if(argc != 4) die("Need an id to get");

            Database_get(conn, id);
            break;

        case 's':
            if(argc != 6) die("Need id, name, email to set");
            Database_set(conn, id, argv[4], argv[5]);
            Database_write(conn);
            break;

        case 'd':
            if(argc != 4) die("Need id to delete");

            Database_delete(conn, id);
            Database_write(conn);
            break;

        case 'l':
            Database_list(conn);
            break;
        default:
            die("Invalid action, only: c=create, g=get, s=set, d=del, l=list");
    }

    Database_close(conn);

    return 0;
}