Dự án cuối khoá: 3 app nhiều module

task.h - interface: Model trong suốt + Store opaque

#ifndef TASK_H
#define TASK_H
#include <stdbool.h>

/* Model: mot viec can lam (struct nho, trong suot) */
typedef struct {
    int  id;
    char title[80];
    bool done;
} Task;

/* Store: kho chua cac Task - OPAQUE (giau cau truc o .c) */
typedef struct TaskStore TaskStore;

TaskStore *store_create(void);
void       store_destroy(TaskStore *s);

int   store_add(TaskStore *s, const char *title); /* tra id moi; -1 neu loi */
bool  store_done(TaskStore *s, int id);           /* danh dau xong */
bool  store_remove(TaskStore *s, int id);
int   store_count(const TaskStore *s);
Task *store_at(TaskStore *s, int index);          /* lay theo chi so de in */

bool  store_save(const TaskStore *s, const char *path);
bool  store_load(TaskStore *s, const char *path);

#endif

store.c - implementation (mảng động) + storage

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "task.h"

struct TaskStore {          /* chi file nay biet bo cuc */
    Task *items;
    int   len, cap;
    int   next_id;          /* id tu tang, khong trung */
};

TaskStore *store_create(void) {
    TaskStore *s = malloc(sizeof *s);
    if (!s) return NULL;
    s->items = NULL; s->len = s->cap = 0; s->next_id = 1;
    return s;
}

void store_destroy(TaskStore *s) {
    if (!s) return;
    free(s->items);         /* tra lai bo nho da xin */
    free(s);
}

static bool grow(TaskStore *s) {               /* RIENG (static): tang gap doi khi day */
    if (s->len < s->cap) return true;
    int cap = s->cap ? s->cap * 2 : 4;
    Task *p = realloc(s->items, (size_t)cap * sizeof *p);
    if (!p) return false;
    s->items = p; s->cap = cap;
    return true;
}

int store_add(TaskStore *s, const char *title) {
    if (!grow(s)) return -1;
    Task *t = &s->items[s->len++];
    t->id = s->next_id++;
    snprintf(t->title, sizeof t->title, "%s", title);
    t->done = false;
    return t->id;
}

static Task *find(TaskStore *s, int id) {      /* RIENG: tim theo id */
    for (int i = 0; i < s->len; i++)
        if (s->items[i].id == id) return &s->items[i];
    return NULL;
}

bool store_done(TaskStore *s, int id) {
    Task *t = find(s, id);
    if (!t) return false;
    t->done = true;
    return true;
}

bool store_remove(TaskStore *s, int id) {
    for (int i = 0; i < s->len; i++)
        if (s->items[i].id == id) {
            s->items[i] = s->items[--s->len];  /* lap muc cuoi vao cho trong */
            return true;
        }
    return false;
}

int   store_count(const TaskStore *s) { return s->len; }
Task *store_at(TaskStore *s, int i) { return (i >= 0 && i < s->len) ? &s->items[i] : NULL; }

/* --- Storage: moi dong la "id|done|title" --- */
bool store_save(const TaskStore *s, const char *path) {
    FILE *f = fopen(path, "w");
    if (!f) return false;
    for (int i = 0; i < s->len; i++)
        fprintf(f, "%d|%d|%s\n", s->items[i].id, s->items[i].done, s->items[i].title);
    fclose(f);
    return true;
}

bool store_load(TaskStore *s, const char *path) {
    FILE *f = fopen(path, "r");
    if (!f) return true;        /* chua co file = danh sach rong, khong loi */
    char line[160];
    while (fgets(line, sizeof line, f)) {
        int id, done; char title[80];
        if (sscanf(line, "%d|%d|%79[^\n]", &id, &done, title) == 3) {
            store_add(s, title);
            Task *t = &s->items[s->len - 1];
            t->id = id; t->done = (done != 0);
            if (id >= s->next_id) s->next_id = id + 1;
        }
    }
    fclose(f);
    return true;
}

main.c - CLI: them / xong / xoa / in / thoat

#include <stdio.h>
#include <string.h>
#include "task.h"

#define FILE_PATH "todo.dat"

static void in_danh_sach(TaskStore *s) {
    int n = store_count(s), chua = 0;
    for (int i = 0; i < n; i++) {
        Task *t = store_at(s, i);
        printf("  #%-3d [%c] %s\n", t->id, t->done ? 'x' : ' ', t->title);
        if (!t->done) chua++;
    }
    if (n == 0) printf("  (trong)\n");
    printf("  -- con %d viec chua xong --\n", chua);
}

int main(void) {
    TaskStore *s = store_create();
    if (!s) return 1;
    store_load(s, FILE_PATH);

    char dong[120];
    printf("Lenh: them <viec> | xong <id> | xoa <id> | in | thoat\n");
    while (printf("> "), fgets(dong, sizeof dong, stdin)) {
        char cmd[16]; int id;
        if (sscanf(dong, "%15s", cmd) != 1) continue;

        if (strcmp(cmd, "them") == 0) {
            char *viec = dong + 4;                  /* bo qua "them " */
            while (*viec == ' ') viec++;
            viec[strcspn(viec, "\n")] = '\0';       /* bo ky tu xuong dong */
            if (*viec) printf("  + #%d\n", store_add(s, viec));
        } else if (strcmp(cmd, "xong") == 0 && sscanf(dong, "%*s %d", &id) == 1) {
            if (store_done(s, id)) printf("  da xong #%d\n", id);
            else printf("  khong thay #%d\n", id);
        } else if (strcmp(cmd, "xoa") == 0 && sscanf(dong, "%*s %d", &id) == 1) {
            if (store_remove(s, id)) printf("  da xoa #%d\n", id);
            else printf("  khong thay #%d\n", id);
        } else if (strcmp(cmd, "in") == 0) {
            in_danh_sach(s);
        } else if (strcmp(cmd, "thoat") == 0) {
            break;
        }
    }

    store_save(s, FILE_PATH);    /* luu truoc khi thoat */
    store_destroy(s);            /* tra het bo nho */
    return 0;
}

Lenh: them <viec> | xong <id> | xoa <id> | in | thoat
> them hoc bai C
  + #1
> them di cho
  + #2
> xong 1
  da xong #1
> in
  #1   [x] hoc bai C
  #2   [ ] di cho
  -- con 1 viec chua xong --
> thoat

expense.h - chỉ đổi Model + thêm lệnh tính tổng

typedef struct {
    int  id;
    long amount;           /* dong - SO NGUYEN, KHONG dung float cho tien */
    char category[24];     /* "an uong", "di lai", ... */
    char note[80];
} Expense;

typedef struct ExpenseStore ExpenseStore;
/* create/add/remove/count/at/save/load: GIONG het bo khung Todo, doi Task -> Expense */

long store_total(const ExpenseStore *s);                 /* tong tat ca */
long store_total_of(const ExpenseStore *s, const char *category);  /* tong 1 nhom */

candidate.h - Model + nghiệp vụ bỏ phiếu

typedef struct {
    int  id;
    char name[60];
    int  votes;            /* so phieu - tang dan khi co nguoi bau */
} Candidate;

typedef struct CandidateStore CandidateStore;
/* create/add/remove/count/at/save/load: van la bo khung quen thuoc */

bool       store_vote(CandidateStore *s, int id);   /* tim theo id roi votes++ */
Candidate *store_leader(const CandidateStore *s);   /* ung vien nhieu phieu nhat */