feat: add lru cache and block info pagination (#26)

Description
---
Add pagination to all outpus/inputs/kernels.
Add caching on the express server for this pagination requests.

Motivation and Context
---

How Has This Been Tested?
---
Manually.

What process can a PR reviewer use to test or verify this change?
---
Go to some very heavy block and see that the request is fast and also
lightweight.

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Breaking Changes
---

- [x] None
- [ ] Requires data directory on base node to be deleted
- [ ] Requires hard fork
- [ ] Other - Please specify

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app.js

@@ -73,6 +73,9 @@ hbs.registerHelper("chart", function (data, height) {
 hbs.registerHelper("json", function (obj) {
   return JSON.stringify(obj);
 });
+hbs.registerHelper("add", function (a, b) {
+  return a + b;
+});
 
 hbs.registerPartials(path.join(__dirname, "partials"));
 

cache.js

@@ -0,0 +1,31 @@
+class Cache {
+  constructor(limit = 1000) {
+    this.limit = limit;
+    this.cache = new Map();
+  }
+
+  set(key, value) {
+    if (this.cache.size >= this.limit) {
+      const firstItemKey = this.cache.keys().next().value;
+      this.cache.delete(firstItemKey);
+    }
+    this.cache.set(key, value);
+  }
+
+  async get(func, args) {
+    let cache_key = JSON.stringify(args);
+    if (this.cache.has(cache_key)) {
+      const temp = this.cache.get(cache_key);
+      this.cache.delete(cache_key);
+      this.cache.set(cache_key, temp);
+      return temp;
+    }
+    let result = await func(args);
+    console.log("Actual call", args);
+    this.set(cache_key, result);
+    return result;
+  }
+}
+
+var cache = new Cache();
+module.exports = cache;

routes/blocks.js

@@ -23,6 +23,7 @@
 var { createClient } = require("../baseNodeClient");
 
 var express = require("express");
+const cache = require("../cache");
 var router = express.Router();
 
 function fromHexString(hexString) {
@@ -56,13 +57,151 @@ router.get("/:height_or_hash", async function (req, res) {
       height = parseInt(height_or_hash);
     }
 
-    block = await client.getBlocks({ heights: [height] });
+    let request = { heights: [height] };
+    block = await cache.get(client.getBlocks, request);
     if (!block || block.length === 0) {
       res.status(404);
       res.render("404", { message: `Block at height ${height} not found` });
       return;
     }
 
+    let outputs_from = +(req.query.outputs_from || 0);
+    let outputs_to = +(req.query.outputs_to || 10);
+    let inputs_from = req.query.inputs_from || 0;
+    let inputs_to = +(req.query.inputs_to || 10);
+    let kernels_from = +(req.query.kernels_from || 0);
+    let kernels_to = +(req.query.kernels_to || 10);
+    let body = {
+      outputs_length: block[0].block.body.outputs.length,
+      inputs_length: block[0].block.body.inputs.length,
+      kernels_length: block[0].block.body.kernels.length,
+      outputs: block[0].block.body.outputs.slice(outputs_from, outputs_to),
+      inputs: block[0].block.body.inputs.slice(inputs_from, inputs_to),
+      kernels: block[0].block.body.kernels.slice(kernels_from, kernels_to),
+      outputsNext: null,
+      outputsNextLink: null,
+      outputsPrev: null,
+      outputsPrevLink: null,
+      outputsFrom: outputs_from,
+      inputsNext: null,
+      inputsNextLink: null,
+      inputsPrev: null,
+      inputsPrevLink: null,
+      inputsFrom: inputs_from,
+      kernelsNext: null,
+      kernelsNextLink: null,
+      kernelsPrev: null,
+      kernelsPrevLink: null,
+      kernelsFrom: kernels_from,
+    };
+    if (outputs_from > 0) {
+      body.outputsPrev = `${outputs_from - 10}..${outputs_from - 1}`;
+      body.outputsPrevLink =
+        "/blocks/" +
+        height +
+        "?outputs_from=" +
+        (outputs_from - 10) +
+        "&outputs_to=" +
+        (outputs_to - 10) +
+        "&inputs_from=" +
+        inputs_from +
+        "&inputs_to=" +
+        inputs_to +
+        "&kernels_from=" +
+        kernels_from +
+        "&kernels_to=" +
+        kernels_to;
+    }
+    if (outputs_to < body.outputs_length) {
+      body.outputsNext = `${outputs_to}..${outputs_to + 9}`;
+      body.outputsNextLink =
+        "/blocks/" +
+        height +
+        "?outputs_from=" +
+        (outputs_from + 10) +
+        "&outputs_to=" +
+        (outputs_to + 10) +
+        "&inputs_from=" +
+        inputs_from +
+        "&inputs_to=" +
+        inputs_to +
+        "&kernels_from=" +
+        kernels_from +
+        "&kernels_to=" +
+        kernels_to;
+    }
+    if (inputs_from > 0) {
+      body.inputsPrev = `${inputs_from - 10}..${inputs_from - 1}`;
+      body.inputsPrevLink =
+        "/blocks/" +
+        height +
+        "?outputs_from=" +
+        outputs_from +
+        "&outputs_to=" +
+        outputs_to +
+        "&inputs_from=" +
+        (inputs_from - 10) +
+        "&inputs_to=" +
+        (inputs_to - 10) +
+        "&kernels_from=" +
+        kernels_from +
+        "&kernels_to=" +
+        kernels_to;
+    }
+    if (inputs_to < body.inputs_length) {
+      body.inputsNext = `${inputs_to}..${inputs_to + 9}`;
+      body.inputsNextLink =
+        "/blocks/" +
+        height +
+        "?outputs_from=" +
+        outputs_from +
+        "&outputs_to=" +
+        outputs_to +
+        "&inputs_from=" +
+        (inputs_from + 10) +
+        "&inputs_to=" +
+        (inputs_to + 10) +
+        "&kernels_from=" +
+        kernels_from +
+        "&kernels_to=" +
+        kernels_to;
+    }
+    if (kernels_from > 0) {
+      body.kernelsPrev = `${kernels_from - 10}..${kernels_from - 1}`;
+      body.kernelsPrevLink =
+        "/blocks/" +
+        height +
+        "?outputs_from=" +
+        outputs_from +
+        "&outputs_to=" +
+        outputs_to +
+        "&inputs_from=" +
+        inputs_from +
+        "&inputs_to=" +
+        inputs_to +
+        "&kernels_from=" +
+        (kernels_from - 10) +
+        "&kernels_to=" +
+        (kernels_to - 10);
+    }
+    if (kernels_to < body.kernels_length) {
+      body.kernelsNext = `${kernels_to}..${kernels_to + 9}`;
+      body.kernelsNextLink =
+        "/blocks/" +
+        height +
+        "?outputs_from=" +
+        outputs_from +
+        "&outputs_to=" +
+        outputs_to +
+        "&inputs_from=" +
+        inputs_from +
+        "&inputs_to=" +
+        inputs_to +
+        "&kernels_from=" +
+        (kernels_from + 10) +
+        "&kernels_to=" +
+        (kernels_to + 10);
+    }
     let tipInfo = await client.getTipInfo({});
     let tipHeight = parseInt(tipInfo.metadata.best_block_height);
 
@@ -82,7 +221,7 @@ router.get("/:height_or_hash", async function (req, res) {
       prevHeight,
       nextLink,
       nextHeight,
-      block: block[0].block,
+      body: body,
       pows: { 0: "Monero", 1: "SHA-3" },
     };
     if (req.query.json !== undefined) {

views/blocks.hbs

@@ -73,20 +73,28 @@
   </tr>
 </table>
 
-{{#with this.block.body}}
+{{#with this.body}}
   <table>
     <thead>
       <tr>
         <th>
-          <h2>Outputs({{outputs.length}})</h2>
+          <h2>Outputs({{outputs_length}})</h2>
+          <p>
+            {{#if outputsPrevLink}}
+              <a href="{{outputsPrevLink}}">&lt Outputs {{outputsPrev}}</a>
+            {{/if}}
+            {{#if outputsNextLink}}
+              <a href="{{outputsNextLink}}">Outputs {{outputsNext}} &gt;</a>
+            {{/if}}
+          </p>
         </th>
       </tr>
     </thead>
     <tbody>
       {{#each outputs as |output|}}
         <tr>
           <td>
-            <h3>Output {{@index}}</h3>
+            <h3>Output {{add @index ../outputsFrom}}</h3>
             {{>TransactionOutput output}}
           </td>
         </tr>
@@ -98,15 +106,23 @@
     <thead>
       <tr>
         <th>
-          <h2>Inputs({{inputs.length}})</h2>
+          <h2>Inputs({{inputs_length}})</h2>
+          <p>
+            {{#if inputsPrevLink}}
+              <a href="{{inputsPrevLink}}">&lt Inputs {{inputsPrev}}</a>
+            {{/if}}
+            {{#if inputsNextLink}}
+              <a href="{{inputsNextLink}}">Inputs {{inputsNext}} &gt;</a>
+            {{/if}}
+          </p>
         </th>
       </tr>
     </thead>
     <tbody>
       {{#each inputs as |input|}}
         <tr>
           <td>
-            <h3>Input {{@index}}</h4>
+            <h3>Input {{add @index ../inputsFrom}}</h4>
             {{>TransactionInput input}}
           </td>
         </tr>
@@ -118,19 +134,27 @@
     <thead>
       <tr>
         <th>
-          <h2>Kernels({{kernels.length}})</h2>
+          <h2>Kernels({{kernels_length}})</h2>
+          <p>
+            {{#if kernelsPrevLink}}
+              <a href="{{kernelsPrevLink}}">&lt Kernels {{kernelsPrev}}</a>
+            {{/if}}
+            {{#if kernelsNextLink}}
+              <a href="{{kernelsNextLink}}">Kernels {{kernelsNext}} &gt;</a>
+            {{/if}}
+          </p>
         </th>
       </tr>
     </thead>
     <tbody>
       {{#each kernels as |kernel|}}
         <tr>
           <td>
-            <h3>Kernel {{@index}}</h3>
+            <h3>Kernel {{add @index ../kernelsFrom}}</h4>
             {{>TransactionKernel kernel}}
           </td>
         </tr>
       {{/each}}
     </tbody>
   </table>
-{{/with}}
+{{/with}}