/*
 * 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/>.
 */

#include "op.h"
#include <libweb/http.h>
#include <errno.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>

struct op
{
    sqlite3_stmt *stmt;
    struct op_cfg cfg;
};

static int teardown(struct op *const op)
{
    int ret = 0, error;

    if (!op)
        return 0;
    else if ((error = sqlite3_finalize(op->stmt)) != SQLITE_OK)
    {
        fprintf(stderr, "%s: sqlite3_finalize: %s\n", __func__,
            sqlite3_errstr(error));
        ret = -1;
    }

    const struct op_cfg *const cfg = &op->cfg;

    if (cfg->error)
        cfg->error(cfg->args);

    free(op);
    return ret;
}

static void run_error(void *const p)
{
    teardown(p);
}

static int run(const struct http_payload *const pl,
    struct http_response *const r, void *const user, void *const args)
{
    struct op *const op = args;
    sqlite3_stmt *const stmt = op->stmt;
    const struct op_cfg *const cfg = &op->cfg;
    int ret = -1, error = sqlite3_step(stmt);

    switch (error)
    {
        case SQLITE_BUSY:
            break;

        case SQLITE_ROW:
            if (!cfg->row)
            {
                fprintf(stderr, "%s: expected row callback\n", __func__);
                goto failure;
            }
            else if ((ret = cfg->row(op->stmt, pl, r, user, cfg->args)))
                goto failure;

            break;

        case SQLITE_CONSTRAINT:
            sqlite3_reset(op->stmt);

            if (!cfg->constraint)
            {
                fprintf(stderr, "%s: expected constraint callback\n", __func__);
                goto failure;
            }
            else if ((ret = cfg->constraint(cfg->args)))
                goto failure;

            /* Fall through. */
        case SQLITE_DONE:
        {
            const int error = sqlite3_finalize(op->stmt);

            if (error != SQLITE_OK)
            {
                fprintf(stderr, "%s: sqlite3_finalize: %s\n", __func__,
                    sqlite3_errstr(error));
                ret = -1;
                goto failure;
            }
            else if (cfg->end && (ret = cfg->end(pl, r, user, cfg->args)))
                goto failure;

            free(op);
        }
            break;

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

    return 0;

failure:

    if (teardown(op))
    {
        fprintf(stderr, "%s: teardown failed\n", __func__);
        ret = -1;
    }

    return ret;
}

void op_resume(struct op *const op, struct http_response *const r)
{
    *r = (const struct http_response)
    {
        .step.payload = run,
        .free = run_error,
        .args = op
    };
}

struct op *op_run(sqlite3 *const db, const char *const query,
    const struct op_cfg *const cfg, struct http_response *const r)
{
    sqlite3_stmt *stmt = NULL;
    struct op *const ret = malloc(sizeof *ret);

    if (!ret)
    {
        fprintf(stderr, "%s: malloc(3): %s\n", __func__, strerror(errno));
        goto failure;
    }

    const int error = sqlite3_prepare_v2(db, query, -1, &stmt, NULL);

    if (error != SQLITE_OK && error != SQLITE_BUSY)
    {
        fprintf(stderr, "%s: sqlite3_prepare_v2 \"%s\": %s\n", __func__,
            query, sqlite3_errstr(error));
        goto failure;
    }

    *r = (const struct http_response)
    {
        .step.payload = run,
        .free = run_error,
        .args = ret
    };

    *ret = (const struct op)
    {
        .stmt = stmt,
        .cfg = *cfg
    };

    return ret;

failure:
    free(ret);
    sqlite3_finalize(stmt);
    return NULL;
}