feat: local Nostr relay with relay selection, sync, and integration tests

Local Nostr relay (NIP-01) on port 4869 with LittleFS 4MB storage.
All events published locally first, then synced to public relays via REQ-diff.
Relay selection via NIP-11 HTTP probing with NIP-77 scoring and auto-failover.

Components:
- wisp_relay: 16-file local relay (ws_server, storage_engine, sub_manager,
  broadcaster, relay_validator, router, handlers, rate_limiter, nip11,
  deletion, flash_monitor, relay_types)
- esp_littlefs: LittleFS VFS integration (git submodule)
- negentropy: for future NIP-77 binary sync (git submodule)

New source files:
- local_relay.c/h: thin wrapper for relay init/start/publish
- relay_selector.c/h: NIP-11 probe + scoring + auto-failover
- sync_manager.c/h: REQ-diff sync (primary 30min, fallback 6h)

Bug fixes:
- config.c: use-after-free (cJSON_Delete before seed_relays/sync parsing)
- local_relay: moved init to app_main for boot-time start (not gated on STA IP)

Flash layout: 4MB LittleFS partition at 0x500000 for relay_store

Test results (Board B, live hardware):
- Smoke: ping + HTTP 4869 + NIP-11: PASS
- NIP-11 info document: 10/11 PASS
- WS pub/sub (connect, REQ/EOSE, EVENT/OK, CLOSE, concurrent): 6/6 PASS
- Unit tests (relay_validator + relay_selector): 13/13 PASS

Hardware test make targets in physical-router-test-automation/:
- make relay-build, relay-flash-b, relay-test-smoke/nip11/pubsub/sync/full

3 files changed, 1141 insertions, 0 deletions

diff --git a/components/qrcode/CMakeLists.txt b/components/qrcode/CMakeLists.txt
new file mode 100644
index 0000000..347aeed
--- /dev/null
+++ b/components/qrcode/CMakeLists.txt
@@ -0,0 +1,2 @@
+idf_component_register(SRCS "qrcoded.c"
+                       INCLUDE_DIRS "include")
diff --git a/components/qrcode/include/qrcoded.h b/components/qrcode/include/qrcoded.h
new file mode 100755
index 0000000..602f9c0
--- /dev/null
+++ b/components/qrcode/include/qrcoded.h
@@ -0,0 +1,85 @@
+/**
+ * The MIT License (MIT)
+ *
+ * This library is written and maintained by Richard Moore.
+ * Major parts were derived from Project Nayuki's library.
+ *
+ * Copyright (c) 2017 Richard Moore     (https://github.com/ricmoo/QRCode)
+ * Copyright (c) 2017 Project Nayuki    (https://www.nayuki.io/page/qr-code-generator-library)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/**
+ *  Special thanks to Nayuki (https://www.nayuki.io/) from which this library was
+ *  heavily inspired and compared against.
+ *
+ *  See: https://github.com/nayuki/QR-Code-generator/tree/master/cpp
+ */
+
+#ifndef __QRCODE_H_
+#define __QRCODE_H_
+
+#include <stdbool.h>
+#include <stdint.h>
+
+// QR Code Format Encoding
+#define MODE_NUMERIC 0
+#define MODE_ALPHANUMERIC 1
+#define MODE_BYTE 2
+
+// Error Correction Code Levels
+#define ECC_LOW 0
+#define ECC_MEDIUM 1
+#define ECC_QUARTILE 2
+#define ECC_HIGH 3
+
+// If set to non-zero, this library can ONLY produce QR codes at that version
+// This saves a lot of dynamic memory, as the codeword tables are skipped
+#ifndef LOCK_VERSION
+#define LOCK_VERSION 0
+#endif
+
+typedef struct QRCode
+{
+    uint8_t version;
+    uint8_t size;
+    uint8_t ecc;
+    uint8_t mode;
+    uint8_t mask;
+    uint8_t *modules;
+} QRCode;
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif /* __cplusplus */
+
+    uint16_t qrcode_getBufferSize(uint8_t version);
+
+    int8_t qrcode_initText(QRCode *qrcoded, uint8_t *modules, uint8_t version, uint8_t ecc, const char *data);
+    int8_t qrcode_initBytes(QRCode *qrcoded, uint8_t *modules, uint8_t version, uint8_t ecc, uint8_t *data, uint16_t length);
+
+    bool qrcode_getModule(QRCode *qrcoded, uint8_t x, uint8_t y);
+
+#ifdef __cplusplus
+}
+#endif /* __cplusplus */
+
+#endif /* __QRCODE_H_ */
diff --git a/components/qrcode/qrcoded.c b/components/qrcode/qrcoded.c
new file mode 100755
index 0000000..c8825f3
--- /dev/null
+++ b/components/qrcode/qrcoded.c
@@ -0,0 +1,1054 @@
+/**
+ * The MIT License (MIT)
+ *
+ * This library is written and maintained by Richard Moore.
+ * Major parts were derived from Project Nayuki's library.
+ *
+ * Copyright (c) 2017 Richard Moore     (https://github.com/ricmoo/QRCode)
+ * Copyright (c) 2017 Project Nayuki    (https://www.nayuki.io/page/qr-code-generator-library)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/**
+ *  Special thanks to Nayuki (https://www.nayuki.io/) from which this library was
+ *  heavily inspired and compared against.
+ *
+ *  See: https://github.com/nayuki/QR-Code-generator/tree/master/cpp
+ */
+
+#include "qrcoded.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+/* Error Correction Lookup tables */
+
+#if LOCK_VERSION == 0
+
+static const uint16_t NUM_ERROR_CORRECTION_CODEWORDS[4][40] = {
+    // 1,  2,  3,  4,  5,   6,   7,   8,   9,  10,  11,  12,  13,  14,  15,  16,  17,  18,  19,  20,  21,  22,  23,  24,   25,   26,   27,   28,   29,   30,   31,   32,   33,   34,   35,   36,   37,   38,   39,   40    Error correction level
+    {10, 16, 26, 36, 48, 64, 72, 88, 110, 130, 150, 176, 198, 216, 240, 280, 308, 338, 364, 416, 442, 476, 504, 560, 588, 644, 700, 728, 784, 812, 868, 924, 980, 1036, 1064, 1120, 1204, 1260, 1316, 1372},             // Medium
+    {7, 10, 15, 20, 26, 36, 40, 48, 60, 72, 80, 96, 104, 120, 132, 144, 168, 180, 196, 224, 224, 252, 270, 300, 312, 336, 360, 390, 420, 450, 480, 510, 540, 570, 570, 600, 630, 660, 720, 750},                         // Low
+    {17, 28, 44, 64, 88, 112, 130, 156, 192, 224, 264, 308, 352, 384, 432, 480, 532, 588, 650, 700, 750, 816, 900, 960, 1050, 1110, 1200, 1260, 1350, 1440, 1530, 1620, 1710, 1800, 1890, 1980, 2100, 2220, 2310, 2430}, // High
+    {13, 22, 36, 52, 72, 96, 108, 132, 160, 192, 224, 260, 288, 320, 360, 408, 448, 504, 546, 600, 644, 690, 750, 810, 870, 952, 1020, 1050, 1140, 1200, 1290, 1350, 1440, 1530, 1590, 1680, 1770, 1860, 1950, 2040},    // Quartile
+};
+
+static const uint8_t NUM_ERROR_CORRECTION_BLOCKS[4][40] = {
+    // Version: (note that index 0 is for padding, and is set to an illegal value)
+    // 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40    Error correction level
+    {1, 1, 1, 2, 2, 4, 4, 4, 5, 5, 5, 8, 9, 9, 10, 10, 11, 13, 14, 16, 17, 17, 18, 20, 21, 23, 25, 26, 28, 29, 31, 33, 35, 37, 38, 40, 43, 45, 47, 49},     // Medium
+    {1, 1, 1, 1, 1, 2, 2, 2, 2, 4, 4, 4, 4, 4, 6, 6, 6, 6, 7, 8, 8, 9, 9, 10, 12, 12, 12, 13, 14, 15, 16, 17, 18, 19, 19, 20, 21, 22, 24, 25},              // Low
+    {1, 1, 2, 4, 4, 4, 5, 6, 8, 8, 11, 11, 16, 16, 18, 16, 19, 21, 25, 25, 25, 34, 30, 32, 35, 37, 40, 42, 45, 48, 51, 54, 57, 60, 63, 66, 70, 74, 77, 81}, // High
+    {1, 1, 2, 2, 4, 4, 6, 6, 8, 8, 8, 10, 12, 16, 12, 17, 16, 18, 21, 20, 23, 23, 25, 27, 29, 34, 34, 35, 38, 40, 43, 45, 48, 51, 53, 56, 59, 62, 65, 68},  // Quartile
+};
+
+static const uint16_t NUM_RAW_DATA_MODULES[40] = {
+    //  1,   2,   3,   4,    5,    6,    7,    8,    9,   10,   11,   12,   13,   14,   15,   16,   17,
+    208, 359, 567, 807, 1079, 1383, 1568, 1936, 2336, 2768, 3232, 3728, 4256, 4651, 5243, 5867, 6523,
+    //   18,   19,   20,   21,    22,    23,    24,    25,   26,    27,     28,    29,    30,    31,
+    7211, 7931, 8683, 9252, 10068, 10916, 11796, 12708, 13652, 14628, 15371, 16411, 17483, 18587,
+    //    32,    33,    34,    35,    36,    37,    38,    39,    40
+    19723, 20891, 22091, 23008, 24272, 25568, 26896, 28256, 29648};
+
+// @TODO: Put other LOCK_VERSIONS here
+#elif LOCK_VERSION == 3
+
+static const int16_t NUM_ERROR_CORRECTION_CODEWORDS[4] = {
+    26, 15, 44, 36};
+
+static const int8_t NUM_ERROR_CORRECTION_BLOCKS[4] = {
+    1, 1, 2, 2};
+
+static const uint16_t NUM_RAW_DATA_MODULES = 567;
+
+#else
+
+#error Unsupported LOCK_VERSION (add it...)
+
+#endif
+
+static int max(int a, int b)
+{
+    if (a > b)
+    {
+        return a;
+    }
+    return b;
+}
+
+/*
+static int abs(int value) {
+    if (value < 0) { return -value; }
+    return value;
+}
+*/
+
+/* Mode testing and conversion */
+
+static int8_t getAlphanumeric(char c)
+{
+
+    if (c >= '0' && c <= '9')
+    {
+        return (c - '0');
+    }
+    if (c >= 'A' && c <= 'Z')
+    {
+        return (c - 'A' + 10);
+    }
+
+    switch (c)
+    {
+    case ' ':
+        return 36;
+    case '$':
+        return 37;
+    case '%':
+        return 38;
+    case '*':
+        return 39;
+    case '+':
+        return 40;
+    case '-':
+        return 41;
+    case '.':
+        return 42;
+    case '/':
+        return 43;
+    case ':':
+        return 44;
+    }
+
+    return -1;
+}
+
+static bool isAlphanumeric(const char *text, uint16_t length)
+{
+    while (length != 0)
+    {
+        if (getAlphanumeric(text[--length]) == -1)
+        {
+            return false;
+        }
+    }
+    return true;
+}
+
+static bool isNumeric(const char *text, uint16_t length)
+{
+    while (length != 0)
+    {
+        char c = text[--length];
+        if (c < '0' || c > '9')
+        {
+            return false;
+        }
+    }
+    return true;
+}
+
+/* Counting */
+
+// We store the following tightly packed (less 8) in modeInfo
+//               <=9  <=26  <= 40
+// NUMERIC      ( 10,   12,    14);
+// ALPHANUMERIC (  9,   11,    13);
+// BYTE         (  8,   16,    16);
+static char getModeBits(uint8_t version, uint8_t mode)
+{
+    // Note: We use 15 instead of 16; since 15 doesn't exist and we cannot store 16 (8 + 8) in 3 bits
+    // hex(int("".join(reversed([('00' + bin(x - 8)[2:])[-3:] for x in [10, 9, 8, 12, 11, 15, 14, 13, 15]])), 2))
+    unsigned int modeInfo = 0x7bbb80a;
+
+#if LOCK_VERSION == 0 || LOCK_VERSION > 9
+    if (version > 9)
+    {
+        modeInfo >>= 9;
+    }
+#endif
+
+#if LOCK_VERSION == 0 || LOCK_VERSION > 26
+    if (version > 26)
+    {
+        modeInfo >>= 9;
+    }
+#endif
+
+    char result = 8 + ((modeInfo >> (3 * mode)) & 0x07);
+    if (result == 15)
+    {
+        result = 16;
+    }
+
+    return result;
+}
+
+/* BitBucket */
+
+typedef struct BitBucket
+{
+    uint32_t bitOffsetOrWidth;
+    uint16_t capacityBytes;
+    uint8_t *data;
+} BitBucket;
+
+/*
+void bb_dump(BitBucket *bitBuffer) {
+    printf("Buffer: ");
+    for (uint32_t i = 0; i < bitBuffer->capacityBytes; i++) {
+        printf("%02x", bitBuffer->data[i]);
+        if ((i % 4) == 3) { printf(" "); }
+    }
+    printf("\n");
+}
+*/
+
+static uint16_t bb_getGridSizeBytes(uint8_t size)
+{
+    return (((size * size) + 7) / 8);
+}
+
+static uint16_t bb_getBufferSizeBytes(uint32_t bits)
+{
+    return ((bits + 7) / 8);
+}
+
+static void bb_initBuffer(BitBucket *bitBuffer, uint8_t *data, int32_t capacityBytes)
+{
+    bitBuffer->bitOffsetOrWidth = 0;
+    bitBuffer->capacityBytes = capacityBytes;
+    bitBuffer->data = data;
+
+    memset(data, 0, bitBuffer->capacityBytes);
+}
+
+static void bb_initGrid(BitBucket *bitGrid, uint8_t *data, uint8_t size)
+{
+    bitGrid->bitOffsetOrWidth = size;
+    bitGrid->capacityBytes = bb_getGridSizeBytes(size);
+    bitGrid->data = data;
+
+    memset(data, 0, bitGrid->capacityBytes);
+}
+
+static void bb_appendBits(BitBucket *bitBuffer, uint32_t val, uint8_t length)
+{
+    uint32_t offset = bitBuffer->bitOffsetOrWidth;
+    for (int8_t i = length - 1; i >= 0; i--, offset++)
+    {
+        bitBuffer->data[offset >> 3] |= ((val >> i) & 1) << (7 - (offset & 7));
+    }
+    bitBuffer->bitOffsetOrWidth = offset;
+}
+/*
+void bb_setBits(BitBucket *bitBuffer, uint32_t val, int offset, uint8_t length) {
+    for (int8_t i = length - 1; i >= 0; i--, offset++) {
+        bitBuffer->data[offset >> 3] |= ((val >> i) & 1) << (7 - (offset & 7));
+    }
+}
+*/
+static void bb_setBit(BitBucket *bitGrid, uint8_t x, uint8_t y, bool on)
+{
+    uint32_t offset = y * bitGrid->bitOffsetOrWidth + x;
+    uint8_t mask = 1 << (7 - (offset & 0x07));
+    if (on)
+    {
+        bitGrid->data[offset >> 3] |= mask;
+    }
+    else
+    {
+        bitGrid->data[offset >> 3] &= ~mask;
+    }
+}
+
+static void bb_invertBit(BitBucket *bitGrid, uint8_t x, uint8_t y, bool invert)
+{
+    uint32_t offset = y * bitGrid->bitOffsetOrWidth + x;
+    uint8_t mask = 1 << (7 - (offset & 0x07));
+    bool on = ((bitGrid->data[offset >> 3] & (1 << (7 - (offset & 0x07)))) != 0);
+    if (on ^ invert)
+    {
+        bitGrid->data[offset >> 3] |= mask;
+    }
+    else
+    {
+        bitGrid->data[offset >> 3] &= ~mask;
+    }
+}
+
+static bool bb_getBit(BitBucket *bitGrid, uint8_t x, uint8_t y)
+{
+    uint32_t offset = y * bitGrid->bitOffsetOrWidth + x;
+    return (bitGrid->data[offset >> 3] & (1 << (7 - (offset & 0x07)))) != 0;
+}
+
+/* Drawing Patterns */
+
+// XORs the data modules in this QR Code with the given mask pattern. Due to XOR's mathematical
+// properties, calling applyMask(m) twice with the same value is equivalent to no change at all.
+// This means it is possible to apply a mask, undo it, and try another mask. Note that a final
+// well-formed QR Code symbol needs exactly one mask applied (not zero, not two, etc.).
+static void applyMask(BitBucket *modules, BitBucket *isFunction, uint8_t mask)
+{
+    uint8_t size = modules->bitOffsetOrWidth;
+
+    for (uint8_t y = 0; y < size; y++)
+    {
+        for (uint8_t x = 0; x < size; x++)
+        {
+            if (bb_getBit(isFunction, x, y))
+            {
+                continue;
+            }
+
+            bool invert = 0;
+            switch (mask)
+            {
+            case 0:
+                invert = (x + y) % 2 == 0;
+                break;
+            case 1:
+                invert = y % 2 == 0;
+                break;
+            case 2:
+                invert = x % 3 == 0;
+                break;
+            case 3:
+                invert = (x + y) % 3 == 0;
+                break;
+            case 4:
+                invert = (x / 3 + y / 2) % 2 == 0;
+                break;
+            case 5:
+                invert = x * y % 2 + x * y % 3 == 0;
+                break;
+            case 6:
+                invert = (x * y % 2 + x * y % 3) % 2 == 0;
+                break;
+            case 7:
+                invert = ((x + y) % 2 + x * y % 3) % 2 == 0;
+                break;
+            }
+            bb_invertBit(modules, x, y, invert);
+        }
+    }
+}
+
+static void setFunctionModule(BitBucket *modules, BitBucket *isFunction, uint8_t x, uint8_t y, bool on)
+{
+    bb_setBit(modules, x, y, on);
+    bb_setBit(isFunction, x, y, true);
+}
+
+// Draws a 9*9 finder pattern including the border separator, with the center module at (x, y).
+static void drawFinderPattern(BitBucket *modules, BitBucket *isFunction, uint8_t x, uint8_t y)
+{
+    uint8_t size = modules->bitOffsetOrWidth;
+
+    for (int8_t i = -4; i <= 4; i++)
+    {
+        for (int8_t j = -4; j <= 4; j++)
+        {
+            uint8_t dist = max(abs(i), abs(j)); // Chebyshev/infinity norm
+            int16_t xx = x + j, yy = y + i;
+            if (0 <= xx && xx < size && 0 <= yy && yy < size)
+            {
+                setFunctionModule(modules, isFunction, xx, yy, dist != 2 && dist != 4);
+            }
+        }
+    }
+}
+
+// Draws a 5*5 alignment pattern, with the center module at (x, y).
+static void drawAlignmentPattern(BitBucket *modules, BitBucket *isFunction, uint8_t x, uint8_t y)
+{
+    for (int8_t i = -2; i <= 2; i++)
+    {
+        for (int8_t j = -2; j <= 2; j++)
+        {
+            setFunctionModule(modules, isFunction, x + j, y + i, max(abs(i), abs(j)) != 1);
+        }
+    }
+}
+
+// Draws two copies of the format bits (with its own error correction code)
+// based on the given mask and this object's error correction level field.
+static void drawFormatBits(BitBucket *modules, BitBucket *isFunction, uint8_t ecc, uint8_t mask)
+{
+
+    uint8_t size = modules->bitOffsetOrWidth;
+
+    // Calculate error correction code and pack bits
+    uint32_t data = ecc << 3 | mask; // errCorrLvl is uint2, mask is uint3
+    uint32_t rem = data;
+    for (int i = 0; i < 10; i++)
+    {
+        rem = (rem << 1) ^ ((rem >> 9) * 0x537);
+    }
+
+    data = data << 10 | rem;
+    data ^= 0x5412; // uint15
+
+    // Draw first copy
+    for (uint8_t i = 0; i <= 5; i++)
+    {
+        setFunctionModule(modules, isFunction, 8, i, ((data >> i) & 1) != 0);
+    }
+
+    setFunctionModule(modules, isFunction, 8, 7, ((data >> 6) & 1) != 0);
+    setFunctionModule(modules, isFunction, 8, 8, ((data >> 7) & 1) != 0);
+    setFunctionModule(modules, isFunction, 7, 8, ((data >> 8) & 1) != 0);
+
+    for (int8_t i = 9; i < 15; i++)
+    {
+        setFunctionModule(modules, isFunction, 14 - i, 8, ((data >> i) & 1) != 0);
+    }
+
+    // Draw second copy
+    for (int8_t i = 0; i <= 7; i++)
+    {
+        setFunctionModule(modules, isFunction, size - 1 - i, 8, ((data >> i) & 1) != 0);
+    }
+
+    for (int8_t i = 8; i < 15; i++)
+    {
+        setFunctionModule(modules, isFunction, 8, size - 15 + i, ((data >> i) & 1) != 0);
+    }
+
+    setFunctionModule(modules, isFunction, 8, size - 8, true);
+}
+
+// Draws two copies of the version bits (with its own error correction code),
+// based on this object's version field (which only has an effect for 7 <= version <= 40).
+static void drawVersion(BitBucket *modules, BitBucket *isFunction, uint8_t version)
+{
+
+    int8_t size = modules->bitOffsetOrWidth;
+
+#if LOCK_VERSION != 0 && LOCK_VERSION < 7
+    return;
+
+#else
+    if (version < 7)
+    {
+        return;
+    }
+
+    // Calculate error correction code and pack bits
+    uint32_t rem = version; // version is uint6, in the range [7, 40]
+    for (uint8_t i = 0; i < 12; i++)
+    {
+        rem = (rem << 1) ^ ((rem >> 11) * 0x1F25);
+    }
+
+    uint32_t data = version << 12 | rem; // uint18
+
+    // Draw two copies
+    for (uint8_t i = 0; i < 18; i++)
+    {
+        bool bit = ((data >> i) & 1) != 0;
+        uint8_t a = size - 11 + i % 3, b = i / 3;
+        setFunctionModule(modules, isFunction, a, b, bit);
+        setFunctionModule(modules, isFunction, b, a, bit);
+    }
+
+#endif
+}
+
+static void drawFunctionPatterns(BitBucket *modules, BitBucket *isFunction, uint8_t version, uint8_t ecc)
+{
+
+    uint8_t size = modules->bitOffsetOrWidth;
+
+    // Draw the horizontal and vertical timing patterns
+    for (uint8_t i = 0; i < size; i++)
+    {
+        setFunctionModule(modules, isFunction, 6, i, i % 2 == 0);
+        setFunctionModule(modules, isFunction, i, 6, i % 2 == 0);
+    }
+
+    // Draw 3 finder patterns (all corners except bottom right; overwrites some timing modules)
+    drawFinderPattern(modules, isFunction, 3, 3);
+    drawFinderPattern(modules, isFunction, size - 4, 3);
+    drawFinderPattern(modules, isFunction, 3, size - 4);
+
+#if LOCK_VERSION == 0 || LOCK_VERSION > 1
+
+    if (version > 1)
+    {
+
+        // Draw the numerous alignment patterns
+
+        uint8_t alignCount = version / 7 + 2;
+        uint8_t step;
+        if (version != 32)
+        {
+            step = (version * 4 + alignCount * 2 + 1) / (2 * alignCount - 2) * 2; // ceil((size - 13) / (2*numAlign - 2)) * 2
+        }
+        else
+        { // C-C-C-Combo breaker!
+            step = 26;
+        }
+
+        uint8_t alignPositionIndex = alignCount - 1;
+        uint8_t alignPosition[alignCount];
+
+        alignPosition[0] = 6;
+
+        uint8_t size = version * 4 + 17;
+        for (uint8_t i = 0, pos = size - 7; i < alignCount - 1; i++, pos -= step)
+        {
+            alignPosition[alignPositionIndex--] = pos;
+        }
+
+        for (uint8_t i = 0; i < alignCount; i++)
+        {
+            for (uint8_t j = 0; j < alignCount; j++)
+            {
+                if ((i == 0 && j == 0) || (i == 0 && j == alignCount - 1) || (i == alignCount - 1 && j == 0))
+                {
+                    continue; // Skip the three finder corners
+                }
+                else
+                {
+                    drawAlignmentPattern(modules, isFunction, alignPosition[i], alignPosition[j]);
+                }
+            }
+        }
+    }
+
+#endif
+
+    // Draw configuration data
+    drawFormatBits(modules, isFunction, ecc, 0); // Dummy mask value; overwritten later in the constructor
+    drawVersion(modules, isFunction, version);
+}
+
+// Draws the given sequence of 8-bit codewords (data and error correction) onto the entire
+// data area of this QR Code symbol. Function modules need to be marked off before this is called.
+static void drawCodewords(BitBucket *modules, BitBucket *isFunction, BitBucket *codewords)
+{
+
+    uint32_t bitLength = codewords->bitOffsetOrWidth;
+    uint8_t *data = codewords->data;
+
+    uint8_t size = modules->bitOffsetOrWidth;
+
+    // Bit index into the data
+    uint32_t i = 0;
+
+    // Do the funny zigzag scan
+    for (int16_t right = size - 1; right >= 1; right -= 2)
+    { // Index of right column in each column pair
+        if (right == 6)
+        {
+            right = 5;
+        }
+
+        for (uint8_t vert = 0; vert < size; vert++)
+        { // Vertical counter
+            for (int j = 0; j < 2; j++)
+            {
+                uint8_t x = right - j; // Actual x coordinate
+                bool upwards = ((right & 2) == 0) ^ (x < 6);
+                uint8_t y = upwards ? size - 1 - vert : vert; // Actual y coordinate
+                if (!bb_getBit(isFunction, x, y) && i < bitLength)
+                {
+                    bb_setBit(modules, x, y, ((data[i >> 3] >> (7 - (i & 7))) & 1) != 0);
+                    i++;
+                }
+                // If there are any remainder bits (0 to 7), they are already
+                // set to 0/false/white when the grid of modules was initialized
+            }
+        }
+    }
+}
+
+/* Penalty Calculation */
+
+#define PENALTY_N1 3
+#define PENALTY_N2 3
+#define PENALTY_N3 40
+#define PENALTY_N4 10
+
+// Calculates and returns the penalty score based on state of this QR Code's current modules.
+// This is used by the automatic mask choice algorithm to find the mask pattern that yields the lowest score.
+// @TODO: This can be optimized by working with the bytes instead of bits.
+static uint32_t getPenaltyScore(BitBucket *modules)
+{
+    uint32_t result = 0;
+
+    uint8_t size = modules->bitOffsetOrWidth;
+
+    // Adjacent modules in row having same color
+    for (uint8_t y = 0; y < size; y++)
+    {
+
+        bool colorX = bb_getBit(modules, 0, y);
+        for (uint8_t x = 1, runX = 1; x < size; x++)
+        {
+            bool cx = bb_getBit(modules, x, y);
+            if (cx != colorX)
+            {
+                colorX = cx;
+                runX = 1;
+            }
+            else
+            {
+                runX++;
+                if (runX == 5)
+                {
+                    result += PENALTY_N1;
+                }
+                else if (runX > 5)
+                {
+                    result++;
+                }
+            }
+        }
+    }
+
+    // Adjacent modules in column having same color
+    for (uint8_t x = 0; x < size; x++)
+    {
+        bool colorY = bb_getBit(modules, x, 0);
+        for (uint8_t y = 1, runY = 1; y < size; y++)
+        {
+            bool cy = bb_getBit(modules, x, y);
+            if (cy != colorY)
+            {
+                colorY = cy;
+                runY = 1;
+            }
+            else
+            {
+                runY++;
+                if (runY == 5)
+                {
+                    result += PENALTY_N1;
+                }
+                else if (runY > 5)
+                {
+                    result++;
+                }
+            }
+        }
+    }
+
+    uint16_t black = 0;
+    for (uint8_t y = 0; y < size; y++)
+    {
+        uint16_t bitsRow = 0, bitsCol = 0;
+        for (uint8_t x = 0; x < size; x++)
+        {
+            bool color = bb_getBit(modules, x, y);
+
+            // 2*2 blocks of modules having same color
+            if (x > 0 && y > 0)
+            {
+                bool colorUL = bb_getBit(modules, x - 1, y - 1);
+                bool colorUR = bb_getBit(modules, x, y - 1);
+                bool colorL = bb_getBit(modules, x - 1, y);
+                if (color == colorUL && color == colorUR && color == colorL)
+                {
+                    result += PENALTY_N2;
+                }
+            }
+
+            // Finder-like pattern in rows and columns
+            bitsRow = ((bitsRow << 1) & 0x7FF) | color;
+            bitsCol = ((bitsCol << 1) & 0x7FF) | bb_getBit(modules, y, x);
+
+            // Needs 11 bits accumulated
+            if (x >= 10)
+            {
+                if (bitsRow == 0x05D || bitsRow == 0x5D0)
+                {
+                    result += PENALTY_N3;
+                }
+                if (bitsCol == 0x05D || bitsCol == 0x5D0)
+                {
+                    result += PENALTY_N3;
+                }
+            }
+
+            // Balance of black and white modules
+            if (color)
+            {
+                black++;
+            }
+        }
+    }
+
+    // Find smallest k such that (45-5k)% <= dark/total <= (55+5k)%
+    uint16_t total = size * size;
+    for (uint16_t k = 0; black * 20 < (9 - k) * total || black * 20 > (11 + k) * total; k++)
+    {
+        result += PENALTY_N4;
+    }
+
+    return result;
+}
+
+/* Reed-Solomon Generator */
+
+static uint8_t rs_multiply(uint8_t x, uint8_t y)
+{
+    // Russian peasant multiplication
+    // See: https://en.wikipedia.org/wiki/Ancient_Egyptian_multiplication
+    uint16_t z = 0;
+    for (int8_t i = 7; i >= 0; i--)
+    {
+        z = (z << 1) ^ ((z >> 7) * 0x11D);
+        z ^= ((y >> i) & 1) * x;
+    }
+    return z;
+}
+
+static void rs_init(uint8_t degree, uint8_t *coeff)
+{
+    memset(coeff, 0, degree);
+    coeff[degree - 1] = 1;
+
+    // Compute the product polynomial (x - r^0) * (x - r^1) * (x - r^2) * ... * (x - r^{degree-1}),
+    // drop the highest term, and store the rest of the coefficients in order of descending powers.
+    // Note that r = 0x02, which is a generator element of this field GF(2^8/0x11D).
+    uint16_t root = 1;
+    for (uint8_t i = 0; i < degree; i++)
+    {
+        // Multiply the current product by (x - r^i)
+        for (uint8_t j = 0; j < degree; j++)
+        {
+            coeff[j] = rs_multiply(coeff[j], root);
+            if (j + 1 < degree)
+            {
+                coeff[j] ^= coeff[j + 1];
+            }
+        }
+        root = (root << 1) ^ ((root >> 7) * 0x11D); // Multiply by 0x02 mod GF(2^8/0x11D)
+    }
+}
+
+static void rs_getRemainder(uint8_t degree, uint8_t *coeff, uint8_t *data, uint8_t length, uint8_t *result, uint8_t stride)
+{
+    // Compute the remainder by performing polynomial division
+
+    //for (uint8_t i = 0; i < degree; i++) { result[] = 0; }
+    //memset(result, 0, degree);
+
+    for (uint8_t i = 0; i < length; i++)
+    {
+        uint8_t factor = data[i] ^ result[0];
+        for (uint8_t j = 1; j < degree; j++)
+        {
+            result[(j - 1) * stride] = result[j * stride];
+        }
+        result[(degree - 1) * stride] = 0;
+
+        for (uint8_t j = 0; j < degree; j++)
+        {
+            result[j * stride] ^= rs_multiply(coeff[j], factor);
+        }
+    }
+}
+
+/* QrCode */
+
+static int8_t encodeDataCodewords(BitBucket *dataCodewords, const uint8_t *text, uint16_t length, uint8_t version)
+{
+    int8_t mode = MODE_BYTE;
+
+    if (isNumeric((char *)text, length))
+    {
+        mode = MODE_NUMERIC;
+        bb_appendBits(dataCodewords, 1 << MODE_NUMERIC, 4);
+        bb_appendBits(dataCodewords, length, getModeBits(version, MODE_NUMERIC));
+
+        uint16_t accumData = 0;
+        uint8_t accumCount = 0;
+        for (uint16_t i = 0; i < length; i++)
+        {
+            accumData = accumData * 10 + ((char)(text[i]) - '0');
+            accumCount++;
+            if (accumCount == 3)
+            {
+                bb_appendBits(dataCodewords, accumData, 10);
+                accumData = 0;
+                accumCount = 0;
+            }
+        }
+
+        // 1 or 2 digits remaining
+        if (accumCount > 0)
+        {
+            bb_appendBits(dataCodewords, accumData, accumCount * 3 + 1);
+        }
+    }
+    else if (isAlphanumeric((char *)text, length))
+    {
+        mode = MODE_ALPHANUMERIC;
+        bb_appendBits(dataCodewords, 1 << MODE_ALPHANUMERIC, 4);
+        bb_appendBits(dataCodewords, length, getModeBits(version, MODE_ALPHANUMERIC));
+
+        uint16_t accumData = 0;
+        uint8_t accumCount = 0;
+        for (uint16_t i = 0; i < length; i++)
+        {
+            accumData = accumData * 45 + getAlphanumeric((char)(text[i]));
+            accumCount++;
+            if (accumCount == 2)
+            {
+                bb_appendBits(dataCodewords, accumData, 11);
+                accumData = 0;
+                accumCount = 0;
+            }
+        }
+
+        // 1 character remaining
+        if (accumCount > 0)
+        {
+            bb_appendBits(dataCodewords, accumData, 6);
+        }
+    }
+    else
+    {
+        bb_appendBits(dataCodewords, 1 << MODE_BYTE, 4);
+        bb_appendBits(dataCodewords, length, getModeBits(version, MODE_BYTE));
+        for (uint16_t i = 0; i < length; i++)
+        {
+            bb_appendBits(dataCodewords, (char)(text[i]), 8);
+        }
+    }
+
+    //bb_setBits(dataCodewords, length, 4, getModeBits(version, mode));
+
+    return mode;
+}
+
+static void performErrorCorrection(uint8_t version, uint8_t ecc, BitBucket *data)
+{
+
+    // See: http://www.thonky.com/qr-code-tutorial/structure-final-message
+
+#if LOCK_VERSION == 0
+    uint8_t numBlocks = NUM_ERROR_CORRECTION_BLOCKS[ecc][version - 1];
+    uint16_t totalEcc = NUM_ERROR_CORRECTION_CODEWORDS[ecc][version - 1];
+    uint16_t moduleCount = NUM_RAW_DATA_MODULES[version - 1];
+#else
+    uint8_t numBlocks = NUM_ERROR_CORRECTION_BLOCKS[ecc];
+    uint16_t totalEcc = NUM_ERROR_CORRECTION_CODEWORDS[ecc];
+    uint16_t moduleCount = NUM_RAW_DATA_MODULES;
+#endif
+
+    uint8_t blockEccLen = totalEcc / numBlocks;
+    uint8_t numShortBlocks = numBlocks - moduleCount / 8 % numBlocks;
+    uint8_t shortBlockLen = moduleCount / 8 / numBlocks;
+
+    uint8_t shortDataBlockLen = shortBlockLen - blockEccLen;
+
+    uint8_t result[data->capacityBytes];
+    memset(result, 0, sizeof(result));
+
+    uint8_t coeff[blockEccLen];
+    rs_init(blockEccLen, coeff);
+
+    uint16_t offset = 0;
+    uint8_t *dataBytes = data->data;
+
+    // Interleave all short blocks
+    for (uint8_t i = 0; i < shortDataBlockLen; i++)
+    {
+        uint16_t index = i;
+        uint8_t stride = shortDataBlockLen;
+        for (uint8_t blockNum = 0; blockNum < numBlocks; blockNum++)
+        {
+            result[offset++] = dataBytes[index];
+
+#if LOCK_VERSION == 0 || LOCK_VERSION >= 5
+            if (blockNum == numShortBlocks)
+            {
+                stride++;
+            }
+#endif
+            index += stride;
+        }
+    }
+
+    // Version less than 5 only have short blocks
+#if LOCK_VERSION == 0 || LOCK_VERSION >= 5
+    {
+        // Interleave long blocks
+        uint16_t index = shortDataBlockLen * (numShortBlocks + 1);
+        uint8_t stride = shortDataBlockLen;
+        for (uint8_t blockNum = 0; blockNum < numBlocks - numShortBlocks; blockNum++)
+        {
+            result[offset++] = dataBytes[index];
+
+            if (blockNum == 0)
+            {
+                stride++;
+            }
+            index += stride;
+        }
+    }
+#endif
+
+    // Add all ecc blocks, interleaved
+    uint8_t blockSize = shortDataBlockLen;
+    for (uint8_t blockNum = 0; blockNum < numBlocks; blockNum++)
+    {
+
+#if LOCK_VERSION == 0 || LOCK_VERSION >= 5
+        if (blockNum == numShortBlocks)
+        {
+            blockSize++;
+        }
+#endif
+        rs_getRemainder(blockEccLen, coeff, dataBytes, blockSize, &result[offset + blockNum], numBlocks);
+        dataBytes += blockSize;
+    }
+
+    memcpy(data->data, result, data->capacityBytes);
+    data->bitOffsetOrWidth = moduleCount;
+}
+
+// We store the Format bits tightly packed into a single byte (each of the 4 modes is 2 bits)
+// The format bits can be determined by ECC_FORMAT_BITS >> (2 * ecc)
+static const uint8_t ECC_FORMAT_BITS = (0x02 << 6) | (0x03 << 4) | (0x00 << 2) | (0x01 << 0);
+
+/* Public QRCode functions */
+
+uint16_t qrcode_getBufferSize(uint8_t version)
+{
+    return bb_getGridSizeBytes(4 * version + 17);
+}
+
+// @TODO: Return error if data is too big.
+int8_t qrcode_initBytes(QRCode *qrcoded, uint8_t *modules, uint8_t version, uint8_t ecc, uint8_t *data, uint16_t length)
+{
+    uint8_t size = version * 4 + 17;
+    qrcoded->version = version;
+    qrcoded->size = size;
+    qrcoded->ecc = ecc;
+    qrcoded->modules = modules;
+
+    uint8_t eccFormatBits = (ECC_FORMAT_BITS >> (2 * ecc)) & 0x03;
+
+#if LOCK_VERSION == 0
+    uint16_t moduleCount = NUM_RAW_DATA_MODULES[version - 1];
+    uint16_t dataCapacity = moduleCount / 8 - NUM_ERROR_CORRECTION_CODEWORDS[eccFormatBits][version - 1];
+#else
+    version = LOCK_VERSION;
+    uint16_t moduleCount = NUM_RAW_DATA_MODULES;
+    uint16_t dataCapacity = moduleCount / 8 - NUM_ERROR_CORRECTION_CODEWORDS[eccFormatBits];
+#endif
+
+    struct BitBucket codewords;
+    uint8_t codewordBytes[bb_getBufferSizeBytes(moduleCount)];
+    bb_initBuffer(&codewords, codewordBytes, (int32_t)sizeof(codewordBytes));
+
+    // Place the data code words into the buffer
+    int8_t mode = encodeDataCodewords(&codewords, data, length, version);
+
+    if (mode < 0)
+    {
+        return -1;
+    }
+    qrcoded->mode = mode;
+
+    // Add terminator and pad up to a byte if applicable
+    uint32_t padding = (dataCapacity * 8) - codewords.bitOffsetOrWidth;
+    if (padding > 4)
+    {
+        padding = 4;
+    }
+    bb_appendBits(&codewords, 0, padding);
+    bb_appendBits(&codewords, 0, (8 - codewords.bitOffsetOrWidth % 8) % 8);
+
+    // Pad with alternate bytes until data capacity is reached
+    for (uint8_t padByte = 0xEC; codewords.bitOffsetOrWidth < (dataCapacity * 8); padByte ^= 0xEC ^ 0x11)
+    {
+        bb_appendBits(&codewords, padByte, 8);
+    }
+
+    BitBucket modulesGrid;
+    bb_initGrid(&modulesGrid, modules, size);
+
+    BitBucket isFunctionGrid;
+    uint8_t isFunctionGridBytes[bb_getGridSizeBytes(size)];
+    bb_initGrid(&isFunctionGrid, isFunctionGridBytes, size);
+
+    // Draw function patterns, draw all codewords, do masking
+    drawFunctionPatterns(&modulesGrid, &isFunctionGrid, version, eccFormatBits);
+    performErrorCorrection(version, eccFormatBits, &codewords);
+    drawCodewords(&modulesGrid, &isFunctionGrid, &codewords);
+
+    // Find the best (lowest penalty) mask
+    uint8_t mask = 0;
+    int32_t minPenalty = INT32_MAX;
+    for (uint8_t i = 0; i < 8; i++)
+    {
+        drawFormatBits(&modulesGrid, &isFunctionGrid, eccFormatBits, i);
+        applyMask(&modulesGrid, &isFunctionGrid, i);
+        int penalty = getPenaltyScore(&modulesGrid);
+        if (penalty < minPenalty)
+        {
+            mask = i;
+            minPenalty = penalty;
+        }
+        applyMask(&modulesGrid, &isFunctionGrid, i); // Undoes the mask due to XOR
+    }
+
+    qrcoded->mask = mask;
+
+    // Overwrite old format bits
+    drawFormatBits(&modulesGrid, &isFunctionGrid, eccFormatBits, mask);
+
+    // Apply the final choice of mask
+    applyMask(&modulesGrid, &isFunctionGrid, mask);
+
+    return 0;
+}
+
+int8_t qrcode_initText(QRCode *qrcoded, uint8_t *modules, uint8_t version, uint8_t ecc, const char *data)
+{
+    return qrcode_initBytes(qrcoded, modules, version, ecc, (uint8_t *)data, strlen(data));
+}
+
+bool qrcode_getModule(QRCode *qrcoded, uint8_t x, uint8_t y)
+{
+    if (x >= qrcoded->size || y >= qrcoded->size)
+    {
+        return false;
+    }
+
+    uint32_t offset = y * qrcoded->size + x;
+    return (qrcoded->modules[offset >> 3] & (1 << (7 - (offset & 0x07)))) != 0;
+}
+
+/*
+uint8_t qrcode_getHexLength(QRCode *qrcoded) {
+    return ((qrcoded->size * qrcoded->size) + 7) / 4;
+}
+
+void qrcode_getHex(QRCode *qrcoded, char *result) {
+    
+}
+*/