let rbql_suggest = {};

( function() {

rbql_suggest.active_suggest_idx = null; 
rbql_suggest.suggest_list = []
rbql_suggest.apply_suggest_callback = null;
rbql_suggest.autosuggest_header_vars = [];
rbql_suggest.input_id = null;
rbql_suggest.suggest_list_id = null;
rbql_suggest.suggest_entry_class = null;
rbql_suggest.current_join_table_id = null;
rbql_suggest.fetch_join_header_callback = null;



function js_string_escape_column_name(column_name, quote_char) {
    column_name = column_name.replace(/\\/g, '\\\\');
    column_name = column_name.replace(/\n/g, '\\n');
    column_name = column_name.replace(/\r/g, '\\r');
    column_name = column_name.replace(/\t/g, '\\t');
    if (quote_char === "'")
        return column_name.replace(/'/g, "\\'");
    if (quote_char === '"')
        return column_name.replace(/"/g, '\\"');
    return column_name.replace(/`/g, "\\`");
}


function convert_header_to_rbql_variables(header, table_var_prefix) {
    let max_suggest_len = 100; // Suggest UI could become unresponsive if there are too many suggest options to consider
    let result = [];
    for (let h of header) {
        let column_var_options = {orig_column_name: h, table_var_prefix: table_var_prefix};
        if (h.match('^[_a-zA-Z][_a-zA-Z0-9]*$') !== null) {
            column_var_options.dot_var = `${table_var_prefix}.${h}`;
        } else {
            column_var_options.dot_var = null;
        }
        let escaped_column_name = js_string_escape_column_name(h, '"');
        column_var_options.double_q_var = `${table_var_prefix}["${escaped_column_name}"]`;
        escaped_column_name = js_string_escape_column_name(h, "'");
        column_var_options.single_q_var = `${table_var_prefix}['${escaped_column_name}']`;
        result.push(column_var_options);
        if (result.length > max_suggest_len)
            break;
    }
    return result;
}


function initialize_suggest(input_id, suggest_list_id, suggest_entry_class, apply_suggest_callback, header, fetch_join_header_callback=null) {
    if (!header)
        header = [];
    rbql_suggest.autosuggest_header_vars = convert_header_to_rbql_variables(header, 'a');
    rbql_suggest.active_suggest_idx = null; 
    rbql_suggest.suggest_list = []
    rbql_suggest.input_id = input_id;
    rbql_suggest.suggest_list_id = suggest_list_id;
    rbql_suggest.suggest_entry_class = suggest_entry_class;
    rbql_suggest.apply_suggest_callback = apply_suggest_callback;
    rbql_suggest.fetch_join_header_callback = fetch_join_header_callback;
}


function hide_suggest(suggest_div) {
    if (rbql_suggest.active_suggest_idx !== null) {
        suggest_div.style.display = 'none';
        rbql_suggest.active_suggest_idx = null;
        rbql_suggest.suggest_list = [];
    }
}


function apply_suggest(suggest_index) {
    try {
        let rbql_input = document.getElementById(rbql_suggest.input_id);
        rbql_input.value = rbql_suggest.suggest_list[suggest_index][0];
        rbql_input.selectionStart = rbql_suggest.suggest_list[suggest_index][1];
        rbql_input.selectionEnd = rbql_suggest.suggest_list[suggest_index][1];
        rbql_input.focus();
        if (rbql_suggest.apply_suggest_callback) {
            rbql_suggest.apply_suggest_callback(rbql_suggest.suggest_list[suggest_index][0]);
        }
        hide_suggest(document.getElementById(rbql_suggest.suggest_list_id));
    } catch (e) {
        console.error(`Autocomplete error: ${e}`);
    }
}


function register_suggest_callback(button_element, suggest_index) {
    button_element.addEventListener("click", () => {
        apply_suggest(suggest_index);
    });
}


function highlight_active_suggest_entry(do_highlight) {
    let entry_button = document.getElementById(`rbql_suggest_var_${rbql_suggest.active_suggest_idx}`);
    if (!entry_button)
        return;
    if (do_highlight) {
        let active_entry_class = rbql_suggest.suggest_entry_class + '_active';
        entry_button.className = [rbql_suggest.suggest_entry_class, active_entry_class].join(' ');
        entry_button.scrollIntoView();
    } else {
        entry_button.className = rbql_suggest.suggest_entry_class;
    }
}


function remove_children(root_node) {
    while (root_node.firstChild) {
        root_node.removeChild(root_node.firstChild);
    }
}


function show_suggest(suggest_div, query_before_var, relevant_suggest_list, query_after_cursor) {
    let rbql_input = document.getElementById(rbql_suggest.input_id);
    let caret_left_shift = 0;
    try {
        let caret_coordinates = getCaretCoordinates(rbql_input, rbql_input.selectionStart);
        caret_left_shift = caret_coordinates.left ? caret_coordinates.left : 0;
    } catch (e) {
        caret_left_shift = 0;
    }
    remove_children(suggest_div);
    rbql_suggest.active_suggest_idx = 0;
    rbql_suggest.suggest_list = [];
    for (let i = 0; i < relevant_suggest_list.length; i++) {
        let suggest_text = relevant_suggest_list[i];
        let entry_button = document.createElement('button');
        entry_button.className = rbql_suggest.suggest_entry_class;
        entry_button.textContent = suggest_text;
        entry_button.setAttribute('id', `rbql_suggest_var_${i}`);
        register_suggest_callback(entry_button, i);
        suggest_div.appendChild(entry_button);
        rbql_suggest.suggest_list.push([query_before_var + suggest_text + query_after_cursor, (query_before_var + suggest_text).length]);
    }
    highlight_active_suggest_entry(true);
    suggest_div.style.display = 'block';
    let calculated_height = suggest_div.offsetHeight;
    let calculated_width = suggest_div.offsetWidth;
    let box = rbql_input.getBoundingClientRect();
    suggest_div.style.left = Math.max(0, Math.min(box.left + caret_left_shift, box.right - calculated_width)) + 'px';
    suggest_div.style.top = (box.top - calculated_height) + 'px';
}


function switch_active_suggest(direction) {
    if (rbql_suggest.active_suggest_idx === null)
        return false;
    highlight_active_suggest_entry(false);
    if (direction == 'up') {
        rbql_suggest.active_suggest_idx = (rbql_suggest.active_suggest_idx + rbql_suggest.suggest_list.length - 1) % rbql_suggest.suggest_list.length;
    } else {
        rbql_suggest.active_suggest_idx = (rbql_suggest.active_suggest_idx + 1) % rbql_suggest.suggest_list.length;
    }
    highlight_active_suggest_entry(true);
    return true;
}


function is_printable_key_code(keycode) {
    // Taken from here: https://stackoverflow.com/a/12467610/2898283
    return (keycode > 47 && keycode < 58) || keycode == 32 || (keycode > 64 && keycode < 91) || (keycode > 185 && keycode < 193) || (keycode > 218 && keycode < 223);
}


function handle_input_keydown(event) {
    // We need this logic to prevent the caret from going to the start of the input field with the default arrow-up keydown handler
    try {
        if (event.keyCode == 38) {
            if (switch_active_suggest('up'))
                event.preventDefault();
        } else if (event.keyCode == 40) {
            if (switch_active_suggest('down'))
                event.preventDefault();
        } else if (event.keyCode == 39) {
            if (rbql_suggest.active_suggest_idx !== null) {
                apply_suggest(rbql_suggest.active_suggest_idx);
                event.preventDefault();
            }
        }
    } catch (e) {
        console.error(`Autocomplete error: ${e}`);
    }
}


function variable_has_prefix(full_variable, cursor_var_prefix) {
    return full_variable && full_variable.toLowerCase().startsWith(cursor_var_prefix.toLowerCase()) && full_variable != cursor_var_prefix;
}


function get_best_matching_variable(cursor_var_prefix, column_var_options) {
    if (cursor_var_prefix.startsWith(column_var_options.table_var_prefix + '.')) {
        if (variable_has_prefix(column_var_options.dot_var, cursor_var_prefix))
            return column_var_options.dot_var;
        if (variable_has_prefix(column_var_options.table_var_prefix + '.' + column_var_options.orig_column_name, cursor_var_prefix))
            return column_var_options.single_q_var;
    }
    if (variable_has_prefix(column_var_options.single_q_var, cursor_var_prefix))
        return column_var_options.single_q_var;
    if (variable_has_prefix(column_var_options.double_q_var, cursor_var_prefix))
        return column_var_options.double_q_var;
    return null;
}


function get_join_table_id(query) {
    let match = query.match(/ join +([^ ]+)(?: *$| +o$| +on)/i);
    if (!match)
        return null;
    return match[1];
}


function adjust_join_table_header_callback(join_header) {
    if (!join_header || !join_header.length) {
        rbql_suggest.autosuggest_header_vars = rbql_suggest.autosuggest_header_vars.filter(v => v.table_var_prefix != 'b');
    } else {
        let join_header_vars = convert_header_to_rbql_variables(join_header, 'b');
        rbql_suggest.autosuggest_header_vars = rbql_suggest.autosuggest_header_vars.concat(join_header_vars);
    }
}


function handle_input_keyup(event) {
    try {
        if (event.keyCode == 13) {
            if (rbql_suggest.active_suggest_idx !== null)
                apply_suggest(rbql_suggest.active_suggest_idx);
            return;
        }
        if (is_printable_key_code(event.keyCode) || event.keyCode == 8 /* Bakspace */) {
            // We can't move this into the keydown handler because the characters appear in the input box only after keyUp event.
            // Or alternatively we could scan the event.keyCode to find out the next char, but this is additional logic
            let rbql_input = document.getElementById(rbql_suggest.input_id);
            let current_query = rbql_input.value;
            if (rbql_suggest.fetch_join_header_callback !== null) {
                let join_table_id = get_join_table_id(current_query);
                if (rbql_suggest.current_join_table_id != join_table_id) {
                    rbql_suggest.current_join_table_id = join_table_id;
                    if (join_table_id === null) {
                        adjust_join_table_header_callback([]);
                    } else {
                        rbql_suggest.fetch_join_header_callback(join_table_id, adjust_join_table_header_callback)
                    }
                }
            }
            let suggest_div = document.getElementById(rbql_suggest.suggest_list_id);
            hide_suggest(suggest_div);
            let cursor_pos = rbql_input.selectionStart;
            let query_before_cursor = current_query.substr(0, cursor_pos);
            let query_after_cursor = current_query.substr(cursor_pos);
            // TODO improve the match - just find last var-looking expression. The problem with this one - it won't match extended suggest like a.arbitrary-var -> a['arbitrary-var']
            let last_var_prefix_match = query_before_cursor.match(/(?:[^_a-zA-Z0-9])([ab](?:\.[_a-zA-Z0-9]*|\[[^\]]*))$/);
            if (last_var_prefix_match) {
                let relevant_suggest_list = [];
                let cursor_var_prefix = last_var_prefix_match[1];
                let query_before_var = query_before_cursor.substr(0, last_var_prefix_match.index + 1);
                for (let column_var_options of rbql_suggest.autosuggest_header_vars) {
                    let suggested_var = get_best_matching_variable(cursor_var_prefix, column_var_options);
                    if (suggested_var)
                        relevant_suggest_list.push(suggested_var);
                }
                if (relevant_suggest_list.length) {
                    show_suggest(suggest_div, query_before_var, relevant_suggest_list, query_after_cursor);
                }
            }
        }
    } catch (e) {
        console.error(`Autocomplete error: ${e}`);
    }
}


rbql_suggest.initialize_suggest = initialize_suggest;
rbql_suggest.handle_input_keydown = handle_input_keydown;
rbql_suggest.handle_input_keyup = handle_input_keyup;
rbql_suggest.convert_header_to_rbql_variables = convert_header_to_rbql_variables;

} )();