var express = require('express');
    var app     = express();
    var config  = require( './config/app.json' );
    var fs      = require( 'fs' );

    var Fitbit  = require( 'fitbit-oauth2' );

    // Simple token persist functions.
    //
    var tfile = 'fb-token.json';
    var persist = {
        read: function( filename, cb ) {
            fs.readFile( filename, { encoding: 'utf8', flag: 'r' }, function( err, data ) {
                if ( err ) return cb( err );
                try {
                    var token = JSON.parse( data );
                    cb( null, token );
                } catch( err ) {
                    cb( err );
                }
            });
        },
        write: function( filename, token, cb ) {
            console.log( 'persisting new token:', JSON.stringify( token ) );
            fs.writeFile( filename, JSON.stringify( token ), cb );
        }
    };

    // Instanciate a fitbit client.  See example config below.
    //
    var fitbit = new Fitbit( config.fitbit );

    // In a browser, http://localhost:4000/fitbit to authorize a user for the first time.
    //
    app.get('/fitbit', function (req, res) {
        res.redirect( fitbit.authorizeURL() );
    });

    // Callback service parsing the authorization token and asking for the access token.  This
    // endpoint is refered to in config.fitbit.authorization_uri.redirect_uri.  See example
    // config below.
    //
    app.get('/fitbit_auth_callback', function (req, res, next) {
        var code = req.query.code;
        fitbit.fetchToken( code, function( err, token ) {
            if ( err ) return next( err );

            // persist the token
            persist.write( tfile, token, function( err ) {
                if ( err ) return next( err );
                res.redirect( '/fb-profile' );
            });
        });
    });

    // Call an API.  fitbit.request() mimics nodejs request() library, automatically
    // adding the required oauth2 headers.  The callback is a bit different, called
    // with ( err, body, token ).  If token is non-null, this means a refresh has happened
    // and you should persist the new token.
    //
    app.get( '/fb-profile', function( req, res, next ) {
        fitbit.request({
            uri: "https://api.fitbit.com/1/user/-/profile.json",
            method: 'GET',
        }, function( err, body, token ) {
            if ( err ) return next( err );
            var profile = JSON.parse( body );
            // if token is not null, a refesh has happened and we need to persist the new token
            if ( token )
                persist.write( tfile, token, function( err ) {
                    if ( err ) return next( err );
                        res.send( '<pre>' + JSON.stringify( profile, null, 2 ) + '</pre>' );
                });
            else
                res.send( '<pre>' + JSON.stringify( profile, null, 2 ) + '</pre>' );
        });
    });

    app.listen(4000);