feat: add simpler block data pagination (#32)

Description
---
Add simpler block_data pagination request.
`/block_data/<height>&what=<outputs|inputs|kernels>&from=<number>&to=<number>`
it always returns json.

Motivation and Context
---
This will come handy on react frontend.

How Has This Been Tested?
---

What process can a PR reviewer use to test or verify this change?
---
You can test some urls as described above.

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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

@@ -9,8 +9,9 @@ const logger = require("morgan");
 const asciichart = require("asciichart");
 const cors = require("cors");
 
-var favicon = require('serve-favicon');
+var favicon = require("serve-favicon");
 var indexRouter = require("./routes/index");
+var blockDataRouter = require("./routes/block_data");
 var blocksRouter = require("./routes/blocks");
 var mempoolRouter = require("./routes/mempool");
 var searchCommitmentsRouter = require("./routes/search_commitments");
@@ -85,7 +86,7 @@ var app = express();
 app.set("views", path.join(__dirname, "views"));
 app.set("view engine", "hbs");
 
-app.use(favicon(path.join(__dirname,'public','favicon.ico')));
+app.use(favicon(path.join(__dirname, "public", "favicon.ico")));
 app.use(logger("dev"));
 app.use(express.json());
 app.use(
@@ -99,6 +100,7 @@ app.use(cors());
 
 app.use("/", indexRouter);
 app.use("/blocks", blocksRouter);
+app.use("/block_data", blockDataRouter);
 app.use("/assets", assetsRouter);
 app.use("/mempool", mempoolRouter);
 app.use("/search_commitments", searchCommitmentsRouter);

routes/block_data.js

@@ -0,0 +1,101 @@
+// Copyright 2021. The Tari Project
+//
+// Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
+// following conditions are met:
+//
+// 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following
+// disclaimer.
+//
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
+// following disclaimer in the documentation and/or other materials provided with the distribution.
+//
+// 3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote
+// products derived from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+// INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+// USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+var { createClient } = require("../baseNodeClient");
+
+var express = require("express");
+const cache = require("../cache");
+const cacheSettings = require("../cacheSettings");
+var router = express.Router();
+
+function fromHexString(hexString) {
+  let res = [];
+  for (let i = 0; i < hexString.length; i += 2) {
+    res.push(Number("0x" + hexString.substring(i, i + 2)));
+  }
+  return res;
+}
+
+router.get("/:height_or_hash", async function (req, res) {
+  try {
+    let from = +(req.query.from || 0);
+    let to = +(req.query.to || 10);
+    let what = req.query.what;
+    if (what === undefined) {
+      res.status(404);
+      res.render("404", { message: `Invalid request` });
+      return;
+    }
+    let client = createClient();
+    let height_or_hash = req.params.height_or_hash;
+    let block;
+    let height;
+    if (height_or_hash.length === 64) {
+      block = await client.getHeaderByHash({
+        hash: fromHexString(height_or_hash),
+      });
+      if (!block) {
+        res.status(404);
+        res.render("404", {
+          message: `Block with hash ${height_or_hash} not found`,
+        });
+        return;
+      }
+      height = parseInt(block.header.height);
+    } else {
+      height = parseInt(height_or_hash);
+    }
+
+    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 body = {
+      length: block[0].block.body[what].length,
+      data: block[0].block.body[what].slice(from, to),
+    };
+
+    let tipInfo = await client.getTipInfo({});
+    let tipHeight = parseInt(tipInfo.metadata.best_block_height);
+
+    if (height + cacheSettings.oldBlockDeltaTip <= tipHeight) {
+      res.setHeader("Cache-Control", cacheSettings.oldBlocks);
+    } else {
+      res.setHeader("Cache-Control", cacheSettings.newBlocks);
+    }
+
+    let json = {
+      height,
+      body: body,
+    };
+    res.json(json);
+  } catch (error) {
+    res.status(500);
+    res.json({ error: error });
+  }
+});
+
+module.exports = router;