#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <mysql/mysql.h>


/*
CREATE TABLE `device` (
    `id` INT(11) NOT NULL AUTO_INCREMENT PRIMARY KEY,
    `serial` CHAR(10) NOT NULL,
    `pretty` CHAR(20) DEFAULT NULL,
    CONSTRAINT UNIQUE KEY unique_serial (`serial`) USING HASH,
    INDEX pretty_index USING HASH (`pretty`)
) ENGINE = InnoDB CHARSET = utf8 COLLATE = utf8_bin;
*/

static MYSQL* mysql = NULL;

// for convenient bailout if we encounter any errors other than the one I'm trying to demo here. :)
#define REQUIRE(x) do { if ( !(x) ) { fail(#x, __FUNCTION__, __FILE__, __LINE__); } } while(0)

void fail(const char* cond, const char* func, const char* file, int line) {
    fprintf(stderr, "failed condition %s in %s at %s:%d\n", cond, func, file, line);
    if (mysql && mysql_errno(mysql)) {
        fprintf(stderr, "mysql error #%d: '%s'\n", mysql_errno(mysql), mysql_error(mysql));
    }
    exit(1);
}

int main(int argc, char** argv) {
    if (argc != 5) {
        fprintf(stderr, "usage: %s host user password db\n", argv[0]);
        exit(1);
    }

    mysql = mysql_init(NULL);
    REQUIRE(mysql);
    REQUIRE(mysql_real_connect(mysql, argv[1], argv[2], argv[3], argv[4], 0, NULL, 0));

    MYSQL_STMT* stmt = mysql_stmt_init(mysql);
    REQUIRE(stmt);
    const char* sql = "INSERT IGNORE INTO `device` SET `serial`=?, `pretty`=?";
    REQUIRE(0 == mysql_stmt_prepare(stmt, sql, strlen(sql)));

    MYSQL_BIND binds[2];
    memset(binds, 0, sizeof(binds));

    // bind the two strings
    char* inputs[] = {"abcdefgh", "something"};
    unsigned long length[2];
    for (int i=0; i<2; ++i) {
        binds[i].buffer_type = MYSQL_TYPE_STRING;
        binds[i].buffer = inputs[i];
        length[i] = strlen(inputs[i]);
        binds[i].buffer_length = length[i];
        binds[i].length = &length[i];
    }
    REQUIRE(0 == mysql_stmt_bind_param(stmt, binds));

    // execute! This is where the hang occurs.
    // My environment:
    // Computer A, running Ubuntu 16.04.1 LTS, with libmysqlclient.so.20.3.4, and mysql server 5.7.17
    // Computer B, running Ubuntu 14.04.5 LTS, with libmysqlclient.so.18.0.0, and no mysql server
    // Both computers are connecting to the server running on Computer A.
    // Computer B runs fine. Computer A gets stuck down in recv() waiting for more data.
    // My tcpdumps show that the server has sent the "OK" message fine in both cases.
    // My debugger shows that Computer A has received the "OK" message, but calls recv() again.
    // The hang only happens if the cursor type is read-only, and looks related to the
    // CURSOR_TYPE_READ_ONLY check in execute() in libmysql.c
    // Of course, a read-only cursor should not be used for inserts (the python lib I was using was
    // setting it automatically for all cursors), but I'd expect an error for that, not a hang.
    printf("setting statement to read-only.\n");
    unsigned long type = CURSOR_TYPE_READ_ONLY;
    REQUIRE(0 == mysql_stmt_attr_set(stmt, STMT_ATTR_CURSOR_TYPE, &type));
    printf("executing statement.\n");
    REQUIRE(0 == mysql_stmt_execute(stmt));

    REQUIRE(0 == mysql_stmt_close(stmt));
    mysql_close(mysql);
    mysql = NULL;
}