function AutofillService() {
    initAutofill();
};

function initAutofill() {
    AutofillService.prototype.generateFillScript = function (pageDetails, fillUsername, fillPassword) {
        if (!pageDetails) {
            return null;
        }

        var fillScript = {
            documentUUID: pageDetails.documentUUID,
            script: [],
            autosubmit: null,
            properties: {},
            options: {},
            metadata: {}
        };

        var passwordFields = [],
            passwordForms = [];

        for (var i = 0; i < pageDetails.fields.length; i++) {
            if (pageDetails.fields[i].type === 'password') {
                passwordFields.push(pageDetails.fields[i]);
            }
        }

        for (var formKey in pageDetails.forms) {
            for (var j = 0; j < passwordFields.length; j++) {
                if (formKey === passwordFields[j].form) {
                    passwordForms.push(pageDetails.forms[formKey]);
                    break;
                }
            }
        }

        var password = null,
            username = null,
            loginForm = null;

        if (passwordForms.length) {
            if (passwordForms.length > 1) {
                // More than one form with a password field is on the page.
                // This usually occurs when a website has a login and signup form on the same page.
                // Let's try to guess which one is the login form.

                // First let's try to guess the correct login form by examining the form attribute strings
                // for common login form attribute.
                for (i = 0; i < passwordForms.length; i++) {
                    var formDescriptor = (passwordForms[i].htmlName + '~' + passwordForms[i].htmlId +
                        '~' + passwordForms[i].htmlAction).toLowerCase();

                    if (formDescriptor.indexOf('login') !== -1 || formDescriptor.indexOf('log-in') !== -1 ||
                        formDescriptor.indexOf('signin') !== -1 || formDescriptor.indexOf('sign-in') !== -1 ||
                        formDescriptor.indexOf('logon') !== -1 || formDescriptor.indexOf('log-on') !== -1) {
                        loginForm = passwordForms[i];
                        break;
                    }
                }

                if (!loginForm) {
                    // Next we can try to find the login form that only has one password field. Typically
                    // a registration form may have two password fields for password confirmation.
                    for (i = 0; i < passwordForms.length; i++) {
                        var passwordFieldCount = 0;

                        for (j = 0; j < passwordFields.length; j++) {
                            if (passwordForms[i].opid === passwordFields[j].form) {
                                passwordFieldCount++;
                            }
                        }

                        if (passwordFieldCount === 1) {
                            loginForm = passwordForms[i];
                            break;
                        }
                    }
                }
            }

            if (!loginForm) {
                loginForm = passwordForms[0];
            }

            for (i = 0; i < pageDetails.fields.length; i++) {
                var f = pageDetails.fields[i];
                if (f.form === loginForm.opid && f.type === 'password') {
                    password = f;
                    break;
                }
            }

            for (i = 0; i < pageDetails.fields.length; i++) {
                f = pageDetails.fields[i];
                if (f.form === loginForm.opid && (f.type === 'text' || f.type === 'email')
                    && f.elementNumber < password.elementNumber) {
                    username = f;
                }
            }

            if (loginForm.htmlAction) {
                fillScript.autosubmit = { focusOpid: password.opid };
            }
        }
        else if (passwordFields.length === 1) {
            // The page does not have any forms with password fields. Use the one password field on the page and the
            // input field just before it as the username.

            password = passwordFields[0];
            if (password.elementNumber > 0) {
                for (i = 0; i < pageDetails.fields.length; i++) {
                    f = pageDetails.fields[i];
                    if (f.elementNumber > password.elementNumber) {
                        break;
                    }

                    if (f.type === 'text' || f.type === 'email') {
                        username = f;
                    }
                }

                if (!username) {
                    username = pageDetails.fields[password.elementNumber - 1];
                }
            }
        }

        if (username) {
            fillScript.script.push(['click_on_opid', username.opid]);
            fillScript.script.push(['fill_by_opid', username.opid, fillUsername]);
        }

        if (password) {
            fillScript.script.push(['click_on_opid', password.opid]);
            fillScript.script.push(['fill_by_opid', password.opid, fillPassword]);
        }

        return fillScript;
    };
};