#include <gtest/gtest.h>
#include <cstring>

extern "C" {
#include "kiss.h"
}

TEST(KissDecoder, InitState) {
    kiss_decoder_t dec;
    kiss_decoder_init(&dec);
    EXPECT_EQ(dec.state, KISS_STATE_IDLE);
    EXPECT_EQ(dec.len, 0);
}

TEST(KissDecoder, DecodeSimpleFrame) {
    kiss_decoder_t dec;
    kiss_decoder_init(&dec);
    kiss_frame_t frame;

    /* Build frame: FEND [0x00 0xAA 0xBB] FEND */
    EXPECT_FALSE(kiss_decode(&dec, KISS_FEND, &frame));     /* FEND start */
    EXPECT_FALSE(kiss_decode(&dec, 0x00, &frame));          /* type byte */
    EXPECT_FALSE(kiss_decode(&dec, 0xAA, &frame));          /* data */
    EXPECT_FALSE(kiss_decode(&dec, 0xBB, &frame));          /* data */
    EXPECT_TRUE(kiss_decode(&dec, KISS_FEND, &frame));      /* FEND end */

    EXPECT_EQ(frame.port, 0);
    EXPECT_EQ(frame.len, 2);
    EXPECT_EQ(frame.data[0], 0xAA);
    EXPECT_EQ(frame.data[1], 0xBB);
}

TEST(KissDecoder, DecodeWithEscape) {
    kiss_decoder_t dec;
    kiss_decoder_init(&dec);
    kiss_frame_t frame;

    /* Frame with escaped FEND: FEND [0x00 FESC TFEND] FEND */
    EXPECT_FALSE(kiss_decode(&dec, KISS_FEND, &frame));
    EXPECT_FALSE(kiss_decode(&dec, 0x00, &frame));
    EXPECT_FALSE(kiss_decode(&dec, KISS_FESC, &frame));
    EXPECT_FALSE(kiss_decode(&dec, KISS_TFEND, &frame));
    EXPECT_TRUE(kiss_decode(&dec, KISS_FEND, &frame));

    EXPECT_EQ(frame.port, 0);
    EXPECT_EQ(frame.len, 1);
    EXPECT_EQ(frame.data[0], KISS_FEND);
}

TEST(KissDecoder, DecodePortExtraction) {
    kiss_decoder_t dec;
    kiss_decoder_init(&dec);
    kiss_frame_t frame;

    /* Frame with port 2: FEND [0x21 0xAA] FEND (port=2 in upper nibble) */
    EXPECT_FALSE(kiss_decode(&dec, KISS_FEND, &frame));
    EXPECT_FALSE(kiss_decode(&dec, 0x21, &frame));          /* port=2, cmd=1 */
    EXPECT_FALSE(kiss_decode(&dec, 0xAA, &frame));
    EXPECT_TRUE(kiss_decode(&dec, KISS_FEND, &frame));

    EXPECT_EQ(frame.port, 2);
    EXPECT_EQ(frame.len, 1);
    EXPECT_EQ(frame.data[0], 0xAA);
}

TEST(KissEncoder, EncodeSimpleFrame) {
    uint8_t data[] = {0xAA, 0xBB};
    uint8_t dst[32];
    size_t len = kiss_encode(0, data, 2, dst, sizeof(dst));

    EXPECT_EQ(len, 6);  /* FEND type data[2] FEND = 6 bytes */
    EXPECT_EQ(dst[0], KISS_FEND);
    EXPECT_EQ(dst[1], 0x00);  /* type byte */
    EXPECT_EQ(dst[2], 0xAA);
    EXPECT_EQ(dst[3], 0xBB);
    EXPECT_EQ(dst[4], KISS_FEND);
}

TEST(KissEncoder, EncodeWithEscape) {
    uint8_t data[] = {KISS_FEND};
    uint8_t dst[32];
    size_t len = kiss_encode(0, data, 1, dst, sizeof(dst));

    EXPECT_EQ(len, 7);  /* FEND type FESC TFEND FEND = 7 bytes */
    EXPECT_EQ(dst[0], KISS_FEND);
    EXPECT_EQ(dst[1], 0x00);
    EXPECT_EQ(dst[2], KISS_FESC);
    EXPECT_EQ(dst[3], KISS_TFEND);
    EXPECT_EQ(dst[4], KISS_FEND);
}

TEST(KissEncoder, EncodeQuality) {
    uint8_t dst[32];
    size_t len = kiss_encode_quality(-7, -103, dst, sizeof(dst));

    EXPECT_EQ(len, 8);  /* FEND type(0x11) snr rssi_hi rssi_lo FEND */
    EXPECT_EQ(dst[0], KISS_FEND);
    EXPECT_EQ(dst[1], 0x11);  /* port=1, cmd=1 */
    EXPECT_EQ(dst[2], 0xF9);  /* -7 in two's complement */
    EXPECT_EQ(dst[3], 0xFF);  /* -103 >> 8 */
    EXPECT_EQ(dst[4], 0x99);  /* -103 & 0xFF */
    EXPECT_EQ(dst[5], KISS_FEND);
}

TEST(KissEncoder, RoundTrip) {
    uint8_t orig_data[] = {0x11, 0x22, KISS_FEND, KISS_FESC, 0x33};
    uint8_t encoded[64];
    uint8_t decoded_data[64];

    size_t enc_len = kiss_encode(1, orig_data, 5, encoded, sizeof(encoded));
    EXPECT_GT(enc_len, 0);

    kiss_decoder_t dec;
    kiss_decoder_init(&dec);
    kiss_frame_t frame;

    for (size_t i = 0; i < enc_len; i++) {
        if (kiss_decode(&dec, encoded[i], &frame)) {
            EXPECT_EQ(frame.port, 1);
            EXPECT_EQ(frame.len, 5);
            for (int j = 0; j < 5; j++) {
                EXPECT_EQ(frame.data[j], orig_data[j]);
            }
            return;
        }
    }
    FAIL() << "Decoder did not return complete frame";
}

TEST(KissEncoder, BufferOverflow) {
    uint8_t data[] = {0xAA, 0xBB};
    uint8_t dst[3];  /* Too small */
    size_t len = kiss_encode(0, data, 2, dst, sizeof(dst));
    EXPECT_EQ(len, 0);  /* Should return 0 on overflow */
}