var fs = require('fs'); // Filesystem
var express = require('express'); // Express
var bodyParser = require('body-parser'); // Data conversion, JSON parsing

// Set up Express
var app  = express();

app.use(express.static("./")); // Serve static files from root
app.use(express.json()); // Parse JSON in requests
// app.use("/", (req, res, next) => // Finally send a 404 page
// {
//     res.status(404).sendFile("404.html", {"root": "./"});
// });

// Root route, respond with with index.html
app.get("/", function(req, res)
{
    res.sendFile("./index.html");
});

// Posts route, return posts.json
app.get("/posts", function(req, res)
{
    res.json(JSON.parse(fs.readFileSync('./data/posts.json')));
});

// Posts route, digest received post
app.post("/posts", function(req, res)
{
    var postsFile = fs.readFileSync('./data/posts.json');
    var posts = JSON.parse(postsFile);

    var incomingData = req.body;
    if (validatePost(incomingData))
    {
        posts.unshift(incomingData);
    }
    else
    {
        res.status(400).json({"error":"Failed to validate post"});
        return;
    }

    fs.writeFile('./data/posts.json', JSON.stringify(posts), (e) =>
    {
        if (e)
        {
            res.sendStatus(500);
            throw e;
        }
    });

    res.sendStatus(204);
});

// About route, return about.json
app.get("/about", (req, res) =>
{
    res.json(JSON.parse(fs.readFileSync('./data/about.json')));
});

// Start listening
app.listen(8080, function()
{
    console.log("Listening on port 8080");
});

// Validates a post object conforms to the standard we're expecting
function validatePost(post)
{
    try
    {
        // Check types of each expected property and assume they're there
        return (typeof post.title === "string" && typeof post.author === "string" && typeof post.date === "number" && Array.isArray(post.tags) && typeof post.content === "string");
    }
    catch (e)
    {
        // Object clearly isn't what we're expecting
        return false;
    }
}