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("./static/")); // Serve static files from /static
app.use(express.json()); // Parse JSON in requests

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

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

    // Verify incoming post matches expected schema
    var incomingData = req.body;
    if (validatePost(incomingData))
    {
        // Prepend the incoming post to the post list
        posts.unshift(incomingData);
    }
    else
    {
        // Complain that we haven't been given what we're expecting
        res.status(400).json({"error":"Failed to validate post"});
        return;
    }

    // Try to save the updated posts object
    fs.writeFile('./data/posts.json', JSON.stringify(posts), (e) =>
    {
        if (e)
        {
            // Tell the client we've hit a snag and dump the error to the console
            res.sendStatus(500);
            throw e;
        }
    });

    // Tell the client all is good and that they shouldn't expect any content
    res.sendStatus(204);
});

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

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

// Default route, serve static index.html and let AngularJS handle the remainder
app.get("/*", (req, res) =>
{
    res.sendFile("./static/index.html", {root: __dirname})
});

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

// Verifies the post object conforms to the standard we're expecting
// Each post should conform to the following template:
// {
//     "title":"",
//     "author":"",
//     "date":0,
//     "tags":[
//         ""
//     ],
//     "content":""
// }
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;
    }
}