#include "mbed.h"

Serial pc(USBTX, USBRX);

/**
 * Arduino's Serial#Find method (https://www.arduino.cc/en/Serial/Find) adopted to Mbed OS.
 * Does not allocate buffers inside.
 *
 * Example (finding the string 'ready' in a stream):
 *      Serial uart(D1, D0);
 *      uart.baud(115200);
 *
 *      bool found = serial_find(&uart, "ready", 10);
 *      printf("Found it? %d\n", found)
 *
 * @param serial Pointer to an initialized UART Serial object
 * @param str_to_find String to find in the UART stream
 * @param timeout_s Timeout in seconds
 * @returns True if found, false if timed out
 */
static bool serial_find(Serial *serial, const char *str_to_find, uint32_t timeout_s) {
    // Use RTC (instead of interrupt) for timeout detection
    time_t curr = time(NULL);

    bool is_partial_match = false;
    uint16_t match_ix = 0;
    size_t str_to_find_len = strlen(str_to_find);

    while (1) {
        // timeout detection
        if (time(NULL) - curr > timeout_s) return false;

        while (serial->readable()) {
            // also do timeout detection here...
            if (time(NULL) - curr > timeout_s) return false;

            char c = serial->getc();

            if (!is_partial_match) {
                // Find the first character in the stream
                if (c == str_to_find[0]) {
                    if (str_to_find_len == 1) return true;

                    match_ix = 1;
                    is_partial_match = true;
                }
                continue;
            }

            // is_partial_match is correct, check remaining characters
            if (c == str_to_find[match_ix]) {
                if (str_to_find_len == match_ix + 1) return true;

                match_ix++;
            }
            else {
                // not a match anymore, continue
                is_partial_match = false;
            }
        }
    }

    return false;
}

int main() {
    pc.baud(115200);
    pc.printf("Hello world\n");

    // set up connection over UART, e.g. to ESP8266 WiFi module...
    Serial uart(D1, D0);
    uart.baud(115200);

    bool found = serial_find(&uart, "ready", 10);
    printf("Found it? %d\n", found);
}