/*
 * nanobbs, a tiny forums software.
 * Copyright (C) 2025-2026  Xavier Del Campo Romero
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#define _POSIX_C_SOURCE 200809L

#include "endpoints.h"
#include "auth.h"
#include "db.h"
#include "defs.h"
#include "form.h"
#include <dynstr.h>
#include <libweb/form.h>
#include <libweb/http.h>
#include <libweb/html.h>
#include <sodium.h>
#include <sqlite3.h>
#include <errno.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>

struct passwd
{
    bool valid;
    sqlite3 *db;
    sqlite3_stmt *stmt;
    char *username, *old, *new;
};

static void free_passwd(struct passwd *const p)
{
    int error;

    if (!p)
        return;

    sqlite3_finalize(p->stmt);

    if ((error = sqlite3_close(p->db) != SQLITE_OK))
        fprintf(stderr, "%s: sqlite3_close: %s\n", __func__,
            sqlite3_errstr(error));

    free(p->username);
    free(p->old);
    free(p->new);
    free(p);
}

static int row(struct passwd *const p)
{
    char *const hashpwd = db_str(p->db, p->stmt, "password");

    if (!hashpwd)
    {
        fprintf(stderr, "%s: missing password\n", __func__);
        return -1;
    }
    else if (!crypto_pwhash_str_verify(hashpwd, p->old, strlen(p->old)))
        p->valid = true;

    free(hashpwd);
    return 0;
}

static int finalize_update(struct passwd *const p,
    struct http_response *const r)
{
    *r = (const struct http_response){.status = HTTP_STATUS_SEE_OTHER};

    if (http_response_add_header(r, "Location", "/"))
    {
        fprintf(stderr, "%s: http_response_add_header failed\n", __func__);
        return -1;
    }

    free_passwd(p);
    return 0;
}

static int update(const struct http_payload *const pl,
    struct http_response *const r, void *const user, void *const args)
{
    struct passwd *const p = args;
    sqlite3_stmt *const stmt = p->stmt;
    const int error = sqlite3_step(stmt);

    switch (error)
    {
        case SQLITE_BUSY:
            break;

        case SQLITE_DONE:
            if (finalize_update(p, r))
                goto failure;

            break;

        default:
            fprintf(stderr, "%s: sqlite3_step: %s\n", __func__,
                sqlite3_errstr(error));
            sqlite3_reset(stmt);
            goto failure;
    }

    return 0;

failure:
    free_passwd(p);
    return -1;
}

static int prepare_change(struct passwd *const p, struct http_response *const r)
{
    int ret = -1, error;
    struct dynstr d;
    sqlite3_stmt *stmt = NULL;
    char hashpwd[crypto_pwhash_STRBYTES];

    dynstr_init(&d);

    if (crypto_pwhash_str(hashpwd, p->new, strlen(p->new),
        crypto_pwhash_OPSLIMIT_INTERACTIVE, crypto_pwhash_MEMLIMIT_INTERACTIVE))
    {
        fprintf(stderr, "%s: crypto_pwhash_str failed\n", __func__);
        goto end;
    }
    else if (dynstr_append(&d,
        "UPDATE users SET password='%s' WHERE name = '%s';", hashpwd,
        p->username))
    {
        fprintf(stderr, "%s: dynstr_append failed\n", __func__);
        goto end;
    }
    else if ((error = sqlite3_prepare_v2(p->db, d.str, d.len, &stmt, NULL))
        != SQLITE_OK)
    {
        fprintf(stderr, "%s: sqlite3_prepare_v2 \"%s\": %s\n", __func__,
            d.str, sqlite3_errstr(error));
        goto end;
    }

    p->stmt = stmt;

    *r = (const struct http_response)
    {
        .step.payload = update,
        .args = p
    };

    ret = 0;

end:
    dynstr_free(&d);
    return ret;
}

static int finalize(struct passwd *const p, struct http_response *const r)
{
    const int error = sqlite3_finalize(p->stmt);

    p->stmt = NULL;

    if (error != SQLITE_OK)
    {
        fprintf(stderr, "%s: sqlite3_finalize: %s\n", __func__,
            sqlite3_errstr(error));
        return -1;
    }
    else if (!p->valid)
    {
        const int ret = form_unauthorized("Invalid current password", r);

        free_passwd(p);
        return ret;
    }
    else if (prepare_change(p, r))
    {
        fprintf(stderr, "%s: prepare_change failed\n", __func__);
        return -1;
    }

    return 0;
}

static int run_query(const struct http_payload *const pl,
    struct http_response *const r, void *const user, void *const args)
{
    struct passwd *const p = args;
    sqlite3_stmt *const stmt = p->stmt;
    const int error = sqlite3_step(stmt);

    switch (error)
    {
        case SQLITE_BUSY:
            break;

        case SQLITE_DONE:
            if (finalize(p, r))
                goto failure;

            break;

        case SQLITE_ROW:
            if (row(p))
                goto failure;

            break;

        default:
            fprintf(stderr, "%s: sqlite3_step: %s\n", __func__,
                sqlite3_errstr(error));
            sqlite3_reset(stmt);
            goto failure;
    }

    return 0;

failure:
    free_passwd(p);
    return -1;
}

static int passwd(const struct cfg *const cfg, const char *const username,
    const char *const old, const char *const new, sqlite3 *const db,
    struct http_response *const r)
{
    int ret = -1, error;
    struct dynstr d;
    sqlite3_stmt *stmt = NULL;
    char *userdup = NULL, *olddup = NULL, *newdup = NULL;
    struct passwd *p = NULL;

    dynstr_init(&d);

    if (!(userdup = strdup(username))
        || !(olddup = strdup(old))
        || !(newdup = strdup(new)))
    {
        fprintf(stderr, "%s: strdup(3): %s\n", __func__, strerror(errno));
        goto end;
    }
    else if (dynstr_append(&d,
        "SELECT password from users WHERE name = '%s'", username))
    {
        fprintf(stderr, "%s: dynstr_append failed\n", __func__);
        goto end;
    }
    else if ((error = sqlite3_prepare_v2(db, d.str, d.len, &stmt,
        NULL)) != SQLITE_OK)
    {
        fprintf(stderr, "%s: sqlite3_prepare_v2 \"%s\": %s\n", __func__,
            d.str, sqlite3_errstr(error));
        goto end;
    }
    else if (!(p = malloc(sizeof *p)))
    {
        fprintf(stderr, "%s: malloc(3): %s\n", __func__, strerror(errno));
        goto end;
    }

    *p = (const struct passwd)
    {
        .username = userdup,
        .old = olddup,
        .new = newdup,
        .stmt = stmt,
        .db = db
    };

    *r = (const struct http_response)
    {
        .step.payload = run_query,
        .args = p
    };

    ret = 0;

end:

    if (ret)
    {
        free(p);
        free(userdup);
        free(olddup);
        free(newdup);
        sqlite3_finalize(stmt);
    }

    dynstr_free(&d);
    return ret;
}

static int setup(const struct http_payload *const p,
    struct http_response *const r, void *const user, sqlite3 *const db,
    const struct auth_user *const u)
{
    int ret = -1, error;
    struct form *f = NULL;
    const char *old, *new, *cnew;
    const struct cfg *const cfg = user;

    *r = (const struct http_response){0};

    if (!u)
    {
        ret = form_unauthorized("Authentication required", r);
        goto failure;
    }
    else if ((error = form_alloc(p->u.post.data, &f)))
    {
        if ((ret = error) < 0)
            fprintf(stderr, "%s: form_alloc failed\n", __func__);
        else
            ret = form_badreq("Invalid request", r);

        goto failure;
    }
    else if (!(old = form_value(f, "old")))
    {
        ret = form_badreq("Missing old password", r);
        goto failure;
    }
    else if (!(new = form_value(f, "new")))
    {
        ret = form_badreq("Missing new password", r);
        goto failure;
    }
    else if (!(cnew = form_value(f, "cnew")))
    {
        ret = form_badreq("Missing confirmation password", r);
        goto failure;
    }
    else if (strcmp(new, cnew))
    {
        ret = form_badreq("New password mismatch", r);
        goto failure;
    }
    else if (strlen(new) < MINPWDLEN)
    {
        ret = form_shortpwd(r);
        goto failure;
    }
    else if ((ret = passwd(cfg, u->username, old, new, db, r)))
    {
        fprintf(stderr, "%s: passwd failed\n", __func__);
        goto failure;
    }

    form_free(f);
    return 0;

failure:

    if ((error = sqlite3_close(db)) != SQLITE_OK)
        fprintf(stderr, "%s: sqlite3_close: %s\n", __func__,
            sqlite3_errstr(error));

    form_free(f);
    return ret;
}

int ep_passwd(const struct http_payload *const p,
    struct http_response *const r, void *const user)
{
    const int n = auth_validate(p, r, user, setup);

    if (n < 0)
        fprintf(stderr, "%s: auth_validate failed\n", __func__);
    else if (n)
    {
        const struct cfg *const cfg = user;
        sqlite3 *db;

        if (db_open(cfg->dir, &db))
        {
            fprintf(stderr, "%s: db_open failed\n", __func__);
            return -1;
        }

        return setup(p, r, user, db, NULL);
    }

    return n;
}