Init flask template from https://git.ari.lt/templates/flask

Signed-off-by: Arija A. <ari@ari.lt>

src/static/css/base.css

@@ -0,0 +1,68 @@
+:root {
+    color-scheme: dark;
+}
+
+*,
+*::before,
+*::after {
+    -webkit-box-sizing: border-box;
+    box-sizing: border-box;
+
+    word-wrap: break-word;
+
+    scroll-behavior: smooth;
+}
+
+code,
+code *,
+pre,
+pre * {
+    white-space: pre-wrap;
+    white-space: -moz-pre-wrap;
+    white-space: -pre-wrap;
+    white-space: -o-pre-wrap;
+}
+
+html {
+    height: 100%;
+    min-height: 100%;
+}
+
+body {
+    height: auto;
+    min-height: 100%;
+
+    padding: 2rem;
+    min-height: 100vh;
+}
+
+html,
+body {
+    line-height: 1.5;
+}
+
+ol,
+ul,
+ol *,
+ul * {
+    line-height: 1.8;
+}
+
+code {
+    white-space: pre-wrap !important;
+}
+
+@media (prefers-reduced-motion: reduce) {
+    *,
+    *::before,
+    *::after {
+        -webkit-transition: none !important;
+        -o-transition: none !important;
+        transition: none !important;
+        -webkit-animation: none !important;
+        animation: none !important;
+        -webkit-animation-play-state: paused !important;
+        animation-play-state: paused !important;
+        scroll-behavior: auto !important;
+    }
+}

src/static/css/error.css

@@ -0,0 +1,3 @@
+article {
+    text-align: center;
+}

src/static/js/pow.js

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+/**
+ * @licstart The following is the entire license notice for the JavaScript
+ * code in this file.
+ *
+ * Copyright (C) 2025 Arija A. <ari@ari.lt>
+ *
+ * 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/>.
+ *
+ * @licend The above is the entire license notice for the JavaScript code
+ * in this file.
+ */
+
+"use strict";
+
+const pow_text_encoder = new TextEncoder();
+
+/**
+ * Minimal pure JavaScript SHA-256 implementation.
+ */
+function pow_sha256_js(msg_uint8) {
+    const K = new Uint32Array([
+        0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1,
+        0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
+        0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174, 0xe49b69c1, 0xefbe4786,
+        0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
+        0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147,
+        0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
+        0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b,
+        0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
+        0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a,
+        0x5b9cca4f, 0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
+        0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
+    ]);
+
+    function right_rotate(value, amount) {
+        return (value >>> amount) | (value << (32 - amount));
+    }
+
+    const msg_length = msg_uint8.length;
+    const bit_length = msg_length * 8;
+
+    /* Padding */
+    const padded_length =
+        ((msg_length + 9 + 63) >> 6) << 6; /* multiple of 64 */
+    const padded = new Uint8Array(padded_length);
+    padded.set(msg_uint8);
+    padded[msg_length] = 0x80;
+
+    const dv = new DataView(padded.buffer);
+
+    /* Append 64-bit big-endian length */
+    dv.setUint32(
+        padded_length - 8,
+        Math.floor(bit_length / 0x100000000),
+        false,
+    );
+    dv.setUint32(padded_length - 4, bit_length & 0xffffffff, false);
+
+    /* Initial hash values */
+    let h0 = 0x6a09e667;
+    let h1 = 0xbb67ae85;
+    let h2 = 0x3c6ef372;
+    let h3 = 0xa54ff53a;
+    let h4 = 0x510e527f;
+    let h5 = 0x9b05688c;
+    let h6 = 0x1f83d9ab;
+    let h7 = 0x5be0cd19;
+
+    const w = new Uint32Array(64);
+
+    for (let i = 0; i < padded_length; i += 64) {
+        for (let t = 0; t < 16; ++t) {
+            w[t] = dv.getUint32(i + t * 4, false);
+        }
+
+        for (let t = 16; t < 64; ++t) {
+            const s0 =
+                right_rotate(w[t - 15], 7) ^
+                right_rotate(w[t - 15], 18) ^
+                (w[t - 15] >>> 3);
+            const s1 =
+                right_rotate(w[t - 2], 17) ^
+                right_rotate(w[t - 2], 19) ^
+                (w[t - 2] >>> 10);
+            w[t] = (w[t - 16] + s0 + w[t - 7] + s1) >>> 0;
+        }
+
+        let a = h0;
+        let b = h1;
+        let c = h2;
+        let d = h3;
+        let e = h4;
+        let f = h5;
+        let g = h6;
+        let h = h7;
+
+        for (let t = 0; t < 64; ++t) {
+            const S1 =
+                right_rotate(e, 6) ^ right_rotate(e, 11) ^ right_rotate(e, 25);
+            const ch = (e & f) ^ (~e & g);
+            const temp1 = (h + S1 + ch + K[t] + w[t]) >>> 0;
+            const S0 =
+                right_rotate(a, 2) ^ right_rotate(a, 13) ^ right_rotate(a, 22);
+            const maj = (a & b) ^ (a & c) ^ (b & c);
+            const temp2 = (S0 + maj) >>> 0;
+
+            h = g;
+            g = f;
+            f = e;
+            e = (d + temp1) >>> 0;
+            d = c;
+            c = b;
+            b = a;
+            a = (temp1 + temp2) >>> 0;
+        }
+
+        h0 = (h0 + a) >>> 0;
+        h1 = (h1 + b) >>> 0;
+        h2 = (h2 + c) >>> 0;
+        h3 = (h3 + d) >>> 0;
+        h4 = (h4 + e) >>> 0;
+        h5 = (h5 + f) >>> 0;
+        h6 = (h6 + g) >>> 0;
+        h7 = (h7 + h) >>> 0;
+    }
+
+    const hash = new Uint8Array(32);
+    const hash_view = new DataView(hash.buffer);
+
+    hash_view.setUint32(0, h0, false);
+    hash_view.setUint32(4, h1, false);
+    hash_view.setUint32(8, h2, false);
+    hash_view.setUint32(12, h3, false);
+    hash_view.setUint32(16, h4, false);
+    hash_view.setUint32(20, h5, false);
+    hash_view.setUint32(24, h6, false);
+    hash_view.setUint32(28, h7, false);
+
+    return hash;
+}
+
+/**
+ * Compute SHA-256 hash of input Uint8Array.
+ * Uses native crypto.subtle.digest if available, otherwise falls back to pure JS implementation.
+ */
+async function pow_sha256(message_buffer) {
+    if (
+        typeof crypto === "object" &&
+        crypto.subtle &&
+        typeof crypto.subtle.digest === "function"
+    ) {
+        return await crypto.subtle.digest("SHA-256", message_buffer);
+    } else {
+        return pow_sha256_js(message_buffer).buffer;
+    }
+}
+
+/**
+ * Encode a string to Uint8Array using TextEncoder.
+ */
+function pow_str_to_u8(str) {
+    return pow_text_encoder.encode(str);
+}
+
+/**
+ * Check if the hash buffer meets the difficulty.
+ * Difficulty is number of leading zero hex characters (nibbles).
+ * This function checks bytes directly for better performance.
+ */
+function pow_meets_difficulty_bytes(hash_buffer, difficulty) {
+    const hash_bytes = new Uint8Array(hash_buffer);
+    const zero_bytes = Math.floor(difficulty / 2);
+    const half_nibble = difficulty % 2;
+
+    for (let idx = 0; idx < zero_bytes; ++idx) {
+        if (hash_bytes[idx] !== 0) return false;
+    }
+
+    if (half_nibble) {
+        if ((hash_bytes[zero_bytes] & 0xf0) !== 0) return false;
+    }
+
+    return true;
+}
+
+/**
+ * JS Proof-of-Work
+ */
+async function js_proof_of_work(button, difficulty, nonce) {
+    let tries = 0;
+    let solution = 0;
+
+    const nonce_str = nonce.toString();
+
+    const batch_size = 150000;
+
+    while (true) {
+        for (let idx = 0; idx < batch_size; ++idx) {
+            const message = nonce_str + solution.toString();
+            const message_buffer = pow_str_to_u8(message);
+            const hash_buffer = await pow_sha256(message_buffer);
+
+            if (pow_meets_difficulty_bytes(hash_buffer, difficulty)) {
+                button.value = `Computed PoW after ${tries + idx} tries`;
+                return solution.toString();
+            }
+
+            ++solution;
+        }
+
+        tries += batch_size;
+        button.value = `Computing PoW (${tries} tries)`;
+
+        await new Promise((resolve) => setTimeout(resolve, 0));
+    }
+}
+
+/**
+ * WASM Proof-of-Work
+ */
+async function wasm_proof_of_work(button, difficulty, nonce) {
+    let pow_found = false;
+    let pow_solution = null;
+
+    const wasm_path = "/static/js/wasm/pow.wasm";
+
+    const imports = {
+        global: {
+            pow_update: (tries) => {
+                button.value = `Computing PoW (${tries} tries)`;
+            },
+            pow_finish: (tries, solution) => {
+                button.value = `Computed PoW after ${tries} tries`;
+                pow_solution = solution;
+                pow_found = true;
+            },
+        },
+    };
+
+    let response = await fetch(wasm_path);
+    if (!response.ok) {
+        console.warn(`Failed to fetch WASM ${wasm_path}`);
+        return null;
+    }
+
+    let wasm_module;
+    if (
+        "instantiateStreaming" in WebAssembly &&
+        typeof WebAssembly.instantiateStreaming === "function"
+    ) {
+        wasm_module = await WebAssembly.instantiateStreaming(response, imports);
+    } else {
+        const bytes = await response.arrayBuffer();
+        wasm_module = await WebAssembly.instantiate(bytes, imports);
+    }
+
+    const { pow_init, pow_solve_batch, memory } = wasm_module.instance.exports;
+
+    const encoder = new TextEncoder();
+    const nonce_bytes = encoder.encode(nonce);
+    const memory_view = new Uint8Array(memory.buffer);
+    memory_view.set(nonce_bytes, 0);
+
+    pow_init(0, nonce_bytes.length, difficulty);
+
+    while (!pow_found) {
+        const result = pow_solve_batch();
+
+        if (result === 1) {
+            // Solution found, pow_finish callback fired
+            break;
+        } else if (result === -1) {
+            console.error("WASM PoW (initialisation) error.");
+            return null;
+        }
+
+        // Yield to UI between batches
+        await new Promise((resolve) => setTimeout(resolve, 0));
+    }
+
+    return pow_solution === null ? null : pow_solution.toString();
+}
+
+/**
+ * Perform proof of work by finding a solution such that
+ * SHA-256(nonce + solution) hash has leading zeros per difficulty.
+ */
+async function proof_of_work(button, difficulty, nonce) {
+    button.value = "Computing PoW (0 tries)";
+    await new Promise((resolve) => setTimeout(resolve, 0));
+
+    if ("WebAssembly" in window && typeof WebAssembly === "object") {
+        const sol = await wasm_proof_of_work(button, difficulty, nonce);
+        if (sol !== null) {
+            return sol;
+        } else {
+            console.warn(
+                "WebAssembly present but failed to compute PoW using web assembly. Falling back to JavaScript.",
+            );
+        }
+    }
+
+    return await js_proof_of_work(button, difficulty, nonce);
+}
+
+/**
+ * Wrapper to handle form submission and disable button during PoW.
+ */
+async function proof_of_work_powform(form, button, difficulty, nonce) {
+    const was_disabled = button.disabled;
+    button.disabled = true;
+    button.setAttribute("aria-label", "Proof of Work is computing...");
+
+    try {
+        form.elements["pow_solution"].value = await proof_of_work(
+            button,
+            difficulty,
+            nonce,
+        );
+    } finally {
+        button.disabled = was_disabled;
+        button.setAttribute("aria-label", "Submitting...");
+    }
+}
+
+/**
+ * Wrapper to handle form submission and disable button during PoW on page load.
+ */
+function proof_of_work_powform_onload(form_id, button_id, difficulty, nonce) {
+    const form = document.getElementById(form_id);
+    const form_submit = document.getElementById(button_id);
+
+    form.addEventListener("submit", async (evt) => {
+        evt.preventDefault();
+
+        form_submit.disabled = true;
+        await proof_of_work_powform(form, form_submit, difficulty, nonce);
+        form_submit.value = "Submitting...";
+
+        form.submit();
+    });
+}

src/static/js/wasm/.clang-format

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+---
+BasedOnStyle: LLVM
+IndentWidth: 4
+SortIncludes: false
+AlignConsecutiveAssignments: true
+AlignConsecutiveBitFields: true
+AlignConsecutiveMacros: true
+AlignEscapedNewlines: true
+AllowShortCaseLabelsOnASingleLine: true
+AllowShortEnumsOnASingleLine: true
+AllowShortFunctionsOnASingleLine: true
+AllowShortLambdasOnASingleLine: true
+BinPackParameters: false
+IndentCaseBlocks: true
+IndentCaseLabels: true
+IndentExternBlock: true
+IndentGotoLabels: true
+---
+

src/static/js/wasm/compile.sh

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+#!/bin/sh
+
+set -xeu
+
+clang --target=wasm32 -s -O3 -flto=full -fno-trapping-math -funroll-loops -ffast-math -fno-math-errno -fomit-frame-pointer -fstrict-aliasing -fvisibility-inlines-hidden -fvisibility=hidden -std=c99 -Werror -Wpedantic -pedantic-errors -pedantic -nostdlib -Wl,--no-entry -Wl,--export=pow_init -Wl,--export=pow_solve_batch -o pow.wasm pow.c
+chmod 600 pow.wasm

src/static/js/wasm/pow.c

@@ -0,0 +1,203 @@
+#include <stdint.h>
+#include <stddef.h>
+
+#define BATCH_SIZE    150000
+#define MAX_MSG_LEN   256
+#define NONCE_MAX_LEN 128
+
+/* Global state */
+static char solution_str[32];
+static uint8_t hash_output[32];
+static uint8_t message_buffer[MAX_MSG_LEN];
+
+static uint32_t nonce_length     = 0;
+static uint32_t difficulty       = 0;
+static uint64_t current_solution = 0;
+static uint64_t tries            = 0;
+static uint32_t zero_bytes       = 0;
+static uint32_t half_nibble      = 0;
+
+__attribute__((__import_module__("global"), __import_name__("pow_update"))) void
+pow_update(uint64_t tries);
+__attribute__((__import_module__("global"), __import_name__("pow_finish"))) void
+pow_finish(uint64_t tries, uint64_t solution);
+
+static const uint32_t K[64] = {
+    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1,
+    0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
+    0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174, 0xe49b69c1, 0xefbe4786,
+    0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
+    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147,
+    0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
+    0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b,
+    0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
+    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a,
+    0x5b9cca4f, 0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
+    0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
+};
+
+#define ROTR(x, n)   (((x) >> (n)) | ((x) << (32 - (n))))
+#define CH(x, y, z)  (((x) & (y)) ^ (~(x) & (z)))
+#define MAJ(x, y, z) (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))
+#define EP0(x)       (ROTR(x, 2) ^ ROTR(x, 13) ^ ROTR(x, 22))
+#define EP1(x)       (ROTR(x, 6) ^ ROTR(x, 11) ^ ROTR(x, 25))
+#define SIG0(x)      (ROTR(x, 7) ^ ROTR(x, 18) ^ ((x) >> 3))
+#define SIG1(x)      (ROTR(x, 17) ^ ROTR(x, 19) ^ ((x) >> 10))
+
+static inline void g_sha256_hash(uint32_t message_length) {
+    uint32_t h[8] = {0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a,
+                     0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19};
+
+    const uint64_t bit_length    = (uint64_t)message_length * 8;
+    const uint32_t padded_length = ((message_length + 9 + 63) / 64) * 64;
+
+    static uint8_t padded_msg[128];
+
+    for (uint32_t idx = 0; idx < message_length; ++idx) {
+        padded_msg[idx] = message_buffer[idx];
+    }
+    padded_msg[message_length] = 0x80;
+    for (uint32_t idx = message_length + 1; idx < padded_length - 8; ++idx) {
+        padded_msg[idx] = 0;
+    }
+    for (int idx = 0; idx < 8; ++idx) {
+        padded_msg[padded_length - 1 - idx] =
+            (uint8_t)(bit_length >> (8 * idx));
+    }
+
+    for (uint32_t chunk = 0; chunk < padded_length; chunk += 64) {
+        uint32_t w[64];
+        for (int idx = 0; idx < 16; ++idx) {
+            w[idx] = ((uint32_t)padded_msg[chunk + idx * 4] << 24) |
+                     ((uint32_t)padded_msg[chunk + idx * 4 + 1] << 16) |
+                     ((uint32_t)padded_msg[chunk + idx * 4 + 2] << 8) |
+                     ((uint32_t)padded_msg[chunk + idx * 4 + 3]);
+        }
+
+        for (int idx = 16; idx < 64; ++idx) {
+            w[idx] =
+                SIG1(w[idx - 2]) + w[idx - 7] + SIG0(w[idx - 15]) + w[idx - 16];
+        }
+
+        uint32_t a = h[0], b = h[1], c = h[2], d = h[3];
+        uint32_t e = h[4], f = h[5], g = h[6], h_val = h[7];
+
+        for (int idx = 0; idx < 64; ++idx) {
+            const uint32_t t1 = h_val + EP1(e) + CH(e, f, g) + K[idx] + w[idx];
+            const uint32_t t2 = EP0(a) + MAJ(a, b, c);
+            h_val             = g;
+            g                 = f;
+            f                 = e;
+            e                 = d + t1;
+            d                 = c;
+            c                 = b;
+            b                 = a;
+            a                 = t1 + t2;
+        }
+
+        h[0] += a;
+        h[1] += b;
+        h[2] += c;
+        h[3] += d;
+        h[4] += e;
+        h[5] += f;
+        h[6] += g;
+        h[7] += h_val;
+    }
+
+    for (int idx = 0; idx < 8; ++idx) {
+        hash_output[idx * 4]     = (h[idx] >> 24) & 0xFF;
+        hash_output[idx * 4 + 1] = (h[idx] >> 16) & 0xFF;
+        hash_output[idx * 4 + 2] = (h[idx] >> 8) & 0xFF;
+        hash_output[idx * 4 + 3] = h[idx] & 0xFF;
+    }
+}
+
+static inline int uint64_to_str(uint64_t number, char *str) {
+    if (number == 0) {
+        str[0] = '0';
+        str[1] = '\0';
+        return 1;
+    }
+
+    int length    = 0;
+    uint64_t temp = number;
+
+    while (temp > 0) {
+        ++length;
+        temp /= 10;
+    }
+
+    str[length] = '\0';
+
+    for (int idx = length - 1; idx >= 0; --idx) {
+        str[idx] = '0' + (number % 10);
+        number /= 10;
+    }
+
+    return length;
+}
+
+static inline int g_meets_difficulty(void) {
+    for (uint32_t idx = 0; idx < zero_bytes; ++idx) {
+        if (hash_output[idx] != 0) {
+            return 0;
+        }
+    }
+
+    if (half_nibble && (hash_output[zero_bytes] & 0xF0) != 0) {
+        return 0;
+    }
+
+    return 1;
+}
+
+__attribute__((export_name("pow_init"))) void
+pow_init(uintptr_t nonce_ptr, uint32_t _nonce_length, uint32_t _difficulty) {
+    const uint8_t *nonce = (const uint8_t *)nonce_ptr;
+
+    nonce_length =
+        (_nonce_length > NONCE_MAX_LEN) ? NONCE_MAX_LEN : _nonce_length;
+    difficulty       = _difficulty;
+    zero_bytes       = _difficulty / 2;
+    half_nibble      = _difficulty % 2;
+    current_solution = 0;
+    tries            = 0;
+
+    for (uint32_t idx = 0; idx < nonce_length; ++idx) {
+        message_buffer[idx] = nonce[idx];
+    }
+}
+
+__attribute__((export_name("pow_solve_batch"))) int pow_solve_batch(void) {
+    if (nonce_length == 0) {
+        return 0;
+    }
+
+    for (uint32_t batch_idx = 0; batch_idx < BATCH_SIZE; batch_idx++) {
+        const int sol_len = uint64_to_str(current_solution, solution_str);
+        const int message_length = nonce_length + sol_len;
+
+        if (message_length > MAX_MSG_LEN) {
+            return -1;
+        }
+
+        for (int idx = 0; idx < sol_len; ++idx) {
+            message_buffer[nonce_length + idx] = (uint8_t)solution_str[idx];
+        }
+
+        g_sha256_hash(message_length);
+
+        if (g_meets_difficulty()) {
+            pow_finish(tries + batch_idx, current_solution);
+            return 1;
+        }
+
+        ++current_solution;
+    }
+
+    tries += BATCH_SIZE;
+    pow_update(tries);
+
+    return 0;
+}