var Filter = (function () {

function zephyr_stream_name_match(message, operand) {
    // Zephyr users expect narrowing to "social" to also show messages to /^(un)*social(.d)*$/
    // (unsocial, ununsocial, social.d, etc)
    // TODO: hoist the regex compiling out of the closure
    var m = /^(?:un)*(.+?)(?:\.d)*$/i.exec(operand);
    var base_stream_name = operand;
    if (m !== null && m[1] !== undefined) {
        base_stream_name = m[1];
    }
    var related_regexp = new RegExp(/^(un)*/.source + util.escape_regexp(base_stream_name) + /(\.d)*$/.source, 'i');
    return related_regexp.test(message.stream);
}

function zephyr_topic_name_match(message, operand) {
    // Zephyr users expect narrowing to topic "foo" to also show messages to /^foo(.d)*$/
    // (foo, foo.d, foo.d.d, etc)
    // TODO: hoist the regex compiling out of the closure
    var m = /^(.*?)(?:\.d)*$/i.exec(operand);
    var base_topic = m[1];
    var related_regexp;

    // Additionally, Zephyr users expect the empty instance and
    // instance "personal" to be the same.
    if (base_topic === ''
        || base_topic.toLowerCase() === 'personal'
        || base_topic.toLowerCase() === '(instance "")') {
        related_regexp = /^(|personal|\(instance ""\))(\.d)*$/i;
    } else {
        related_regexp = new RegExp(/^/.source + util.escape_regexp(base_topic) + /(\.d)*$/.source, 'i');
    }

    return related_regexp.test(message.subject);
}

function message_in_home(message) {
    if (message.type === "private" || message.mentioned ||
        (page_params.narrow_stream !== undefined &&
         message.stream.toLowerCase() === page_params.narrow_stream.toLowerCase())) {
        return true;
    }

    return stream_data.in_home_view(message.stream_id);
}

function message_matches_search_term(message, operator, operand) {
    switch (operator) {
    case 'is':
        if (operand === 'private') {
            return (message.type === 'private');
        } else if (operand === 'starred') {
            return message.starred;
        } else if (operand === 'mentioned') {
            return message.mentioned;
        } else if (operand === 'alerted') {
            return message.alerted;
        } else if (operand === 'unread') {
            return unread.message_unread(message);
        }
        return true; // is:whatever returns true

    case 'in':
        if (operand === 'home') {
            return message_in_home(message);
        } else if (operand === 'all') {
            return true;
        }
        return true; // in:whatever returns true

    case 'near':
        // this is all handled server side
        return true;

    case 'id':
        return (message.id.toString() === operand);

    case 'stream':
        if (message.type !== 'stream') {
            return false;
        }

        operand = operand.toLowerCase();
        if (page_params.realm_is_zephyr_mirror_realm) {
            return zephyr_stream_name_match(message, operand);
        }

        // Try to match by stream_id if have a valid sub for
        // the operand.
        var stream_id = stream_data.get_stream_id(operand);
        if (stream_id) {
            return (message.stream_id === stream_id);
        }

        // We need this fallback logic in case we have a message
        // loaded for a stream that we are no longer
        // subscribed to (or that was deleted).
        return (message.stream.toLowerCase() === operand);

    case 'topic':
        if (message.type !== 'stream') {
            return false;
        }

        operand = operand.toLowerCase();
        if (page_params.realm_is_zephyr_mirror_realm) {
            return zephyr_topic_name_match(message, operand);
        }
        return (message.subject.toLowerCase() === operand);


    case 'sender':
        return people.id_matches_email_operand(message.sender_id, operand);

    case 'group-pm-with':
        var operand_ids = people.pm_with_operand_ids(operand);
        if (!operand_ids) {
            return false;
        }
        var user_ids = people.group_pm_with_user_ids(message);
        if (!user_ids) {
            return false;
        }
        return (user_ids.includes(operand_ids[0]));
        // We should also check if the current user is in the recipient list (user_ids) of the
        // message, but it is implicit by the fact that the current user has access to the message.

    case 'pm-with':
        // TODO: use user_ids, not emails here
        if (message.type !== 'private') {
            return false;
        }
        operand_ids = people.pm_with_operand_ids(operand);
        if (!operand_ids) {
            return false;
        }
        user_ids = people.pm_with_user_ids(message);
        if (!user_ids) {
            return false;
        }

        return _.isEqual(operand_ids, user_ids);
    }

    return true; // unknown operators return true (effectively ignored)
}


function Filter(operators) {
    if (operators === undefined) {
        this._operators = [];
    } else {
        this._operators = this._canonicalize_operators(operators);
    }
}

var canonical_operators = {from: "sender", subject: "topic"};

Filter.canonicalize_operator = function (operator) {
    operator = operator.toLowerCase();
    if (canonical_operators.hasOwnProperty(operator)) {
        return canonical_operators[operator];
    }
    return operator;
};

Filter.canonicalize_term = function (opts) {
    var negated = opts.negated;
    var operator = opts.operator;
    var operand = opts.operand;

    // Make negated be explicitly false for both clarity and
    // simplifying deepEqual checks in the tests.
    if (!negated) {
        negated = false;
    }

    operator = Filter.canonicalize_operator(operator);

    switch (operator) {
    case 'has':
        // images -> image, etc.
        operand = operand.replace(/s$/, '');
        break;

    case 'stream':
        operand = stream_data.get_name(operand);
        break;
    case 'topic':
        break;
    case 'sender':
    case 'pm-with':
        operand = operand.toString().toLowerCase();
        if (operand === 'me') {
            operand = people.my_current_email();
        }
        break;
    case 'group-pm-with':
        operand = operand.toString().toLowerCase();
        break;
    case 'search':
        // The mac app automatically substitutes regular quotes with curly
        // quotes when typing in the search bar.  Curly quotes don't trigger our
        // phrase search behavior, however.  So, we replace all instances of
        // curly quotes with regular quotes when doing a search.  This is
        // unlikely to cause any problems and is probably what the user wants.
        operand = operand.toString().toLowerCase().replace(/[\u201c\u201d]/g, '"');
        break;
    default:
        operand = operand.toString().toLowerCase();
    }

    // We may want to consider allowing mixed-case operators at some point
    return {
        negated: negated,
        operator: operator,
        operand: operand,
    };
};

/* We use a variant of URI encoding which looks reasonably
   nice and still handles unambiguously cases such as
   spaces in operands.

   This is just for the search bar, not for saving the
   narrow in the URL fragment.  There we do use full
   URI encoding to avoid problematic characters. */
function encodeOperand(operand) {
    return operand.replace(/%/g, '%25')
                  .replace(/\+/g, '%2B')
                  .replace(/ /g, '+')
                  .replace(/"/g, '%22');
}

function decodeOperand(encoded, operator) {
    encoded = encoded.replace(/"/g, '');
    if (_.contains(['group-pm-with','pm-with','sender','from'],operator) === false) {
        encoded = encoded.replace(/\+/g, ' ');
    }
    return util.robust_uri_decode(encoded).trim();
}

// Parse a string into a list of operators (see below).
Filter.parse = function (str) {
    var operators   = [];
    var search_term = [];
    var negated;
    var operator;
    var operand;
    var term;

    // Match all operands that either have no spaces, or are surrounded by
    // quotes, preceded by an optional operator that may have a space after it.
    var matches = str.match(/([^\s:]+: ?)?("[^"]+"?|\S+)/g);
    if (matches === null) {
        return operators;
    }
    _.each(matches, function (token) {
        var parts;
        var operator;
        parts = token.split(':');
        if (token[0] === '"' || parts.length === 1) {
            // Looks like a normal search term.
            search_term.push(token);
        } else {
            // Looks like an operator.
            negated = false;
            operator = parts.shift();
            if (operator[0] === '-') {
                negated = true;
                operator = operator.slice(1);
            }
            operand = decodeOperand(parts.join(':'), operator);

            // We use Filter.operator_to_prefix() checks if the
            // operator is known.  If it is not known, then we treat
            // it as a search for the given string (which may contain
            // a `:`), not as a search operator.
            if (Filter.operator_to_prefix(operator, negated) === '') {
                // Put it as a search term, to not have duplicate operators
                search_term.push(token);
                return;
            }
            term = {negated: negated, operator: operator, operand: operand};
            operators.push(term);
        }
    });
    // NB: Callers of 'parse' can assume that the 'search' operator is last.
    if (search_term.length > 0) {
        operator = 'search';
        operand = search_term.join(' ');
        term = {operator: operator, operand: operand, negated: false};
        operators.push(term);
    }
    return operators;
};

/* Convert a list of operators to a string.
   Each operator is a key-value pair like

       ['subject', 'my amazing subject']

   These are not keys in a JavaScript object, because we
   might need to support multiple operators of the same type.
*/
Filter.unparse = function (operators) {
    var parts = _.map(operators, function (elem) {

        if (elem.operator === 'search') {
            // Search terms are the catch-all case.
            // All tokens that don't start with a known operator and
            // a colon are glued together to form a search term.
            return elem.operand;
        }
        var sign = elem.negated ? '-' : '';
        if (elem.operator === '') {
            return elem.operand;
        }
        return sign + elem.operator + ':' + encodeOperand(elem.operand.toString());
    });
    return parts.join(' ');
};



Filter.prototype = {
    predicate: function Filter_predicate() {
        if (this._predicate === undefined) {
            this._predicate = this._build_predicate();
        }
        return this._predicate;
    },

    operators: function Filter_operators() {
        return this._operators;
    },

    public_operators: function Filter_public_operators() {
        var safe_to_return = _.filter(this._operators, function (value) {
            // Filter out the embedded narrow (if any).
            return !(page_params.narrow_stream !== undefined &&
                     value.operator === "stream" &&
                     value.operand.toLowerCase() === page_params.narrow_stream.toLowerCase());
        });
        return safe_to_return;
    },

    operands: function Filter_get_operands(operator) {
        return _.chain(this._operators)
            .filter(function (elem) { return !elem.negated && (elem.operator === operator); })
            .map(function (elem) { return elem.operand; })
            .value();
    },

    has_operand: function Filter_has_operand(operator, operand) {
        return _.any(this._operators, function (elem) {
            return !elem.negated && (elem.operator === operator && elem.operand === operand);
        });
    },

    has_operator: function Filter_has_operator(operator) {
        return _.any(this._operators, function (elem) {
            if (elem.negated && (!_.contains(['search', 'has'], elem.operator))) {
                return false;
            }
            return elem.operator === operator;
        });
    },

    is_search: function Filter_is_search() {
        return this.has_operator('search');
    },

    can_apply_locally: function Filter_can_apply_locally() {
        return (!this.is_search()) && (!this.has_operator('has'));
    },

    _canonicalize_operators: function Filter__canonicalize_operators(operators_mixed_case) {
        return _.map(operators_mixed_case, function (tuple) {
            return Filter.canonicalize_term(tuple);
        });
    },

    filter_with_new_topic: function Filter_filter_with_new_topic(new_topic) {
        var terms = _.map(this._operators, function (term) {
            var new_term = _.clone(term);
            if (new_term.operator === 'topic' && !new_term.negated) {
                new_term.operand = new_topic;
            }
            return new_term;
        });
        return new Filter(terms);
    },

    has_topic: function Filter_has_topic(stream_name, topic) {
        return this.has_operand('stream', stream_name) && this.has_operand('topic', topic);
    },

    update_email: function (user_id, new_email) {
        _.each(this._operators, function (term) {
            switch (term.operator) {
                case 'group-pm-with':
                case 'pm-with':
                case 'sender':
                case 'from':
                    term.operand = people.update_email_in_reply_to(
                        term.operand,
                        user_id,
                        new_email
                    );
            }
        });
    },

    // Build a filter function from a list of operators.
    _build_predicate: function Filter__build_predicate() {
        var operators = this._operators;

        if (! this.can_apply_locally()) {
            return function () { return true; };
        }

        // FIXME: This is probably pretty slow.
        // We could turn it into something more like a compiler:
        // build JavaScript code in a string and then eval() it.

        return function (message) {
            return _.all(operators, function (term) {
                var ok = message_matches_search_term(message, term.operator, term.operand);
                if (term.negated) {
                    ok = !ok;
                }
                return ok;
            });
        };
    },
};

Filter.operator_to_prefix = function (operator, negated) {
    var verb;

    if (operator === 'search') {
        return negated ? 'exclude' : 'search for';
    }

    verb = negated ? 'exclude ' : '';

    switch (operator) {
    case 'stream':
        return verb + 'stream';

    case 'near':
        return verb + 'messages around';

    case 'has':
        return verb + 'messages with one or more';

    case 'id':
        return verb + 'message ID';

    case 'subject':
    case 'topic':
        return verb + 'topic';

    case 'from':
    case 'sender':
        return verb + 'sent by';

    case 'pm-with':
        return verb + 'private messages with';

    case 'in':
        return verb + 'messages in';

    // Note: We hack around using this in "describe" below.
    case 'is':
        return verb + 'messages that are';

    case 'group-pm-with':
        return verb + 'group private messages including';
    }
    return '';
};

// Convert a list of operators to a human-readable description.
Filter.describe = function (operators) {
    if (operators.length === 0) {
        return 'all messages';
    }

    var parts = [];

    if (operators.length >= 2) {
        var is = function (term, expected) {
            return (term.operator === expected) && !term.negated;
        };

        if (is(operators[0], 'stream') && is(operators[1], 'topic')) {
            var stream = operators[0].operand;
            var topic = operators[1].operand;
            var part = "stream " + stream + ' > ' + topic;
            parts = [part];
            operators = operators.slice(2);
        }
    }

    var more_parts = _.map(operators, function (elem) {
        var operand = elem.operand;
        var canonicalized_operator = Filter.canonicalize_operator(elem.operator);
        if (canonicalized_operator ==='is') {
            var verb = elem.negated ? 'exclude ' : '';
            if (operand === 'private') {
                return verb + 'private messages';
            } else if (operand === 'starred') {
                return verb + 'starred messages';
            } else if (operand === 'mentioned') {
                return verb + '@-mentions';
            } else if (operand === 'alerted') {
                return verb + 'alerted messages';
            } else if (operand === 'unread') {
                return verb + 'unread messages';
            }
            return operand + ' messages';
        }
        var prefix_for_operator = Filter.operator_to_prefix(canonicalized_operator,
                                                            elem.negated);
        if (prefix_for_operator !== '') {
            return prefix_for_operator + ' ' + operand;
        }
        return "unknown operator";
    });
    return parts.concat(more_parts).join(', ');
};


return Filter;

}());
if (typeof module !== 'undefined') {
    module.exports = Filter;
}
