/**
 * This is the common logic for both the Node.js and web browser
 * implementations of `debug()`.
 */

function setup(env) {
    createDebug.debug = createDebug;
    createDebug.default = createDebug;
    createDebug.coerce = coerce;
    createDebug.disable = disable;
    createDebug.enable = enable;
    createDebug.enabled = enabled;
    createDebug.humanize = require('ms');
    createDebug.destroy = destroy;

    Object.keys(env).forEach(key => {
        createDebug[key] = env[key];
    });

    /**
    * The currently active debug mode names, and names to skip.
    */

    createDebug.names = [];
    createDebug.skips = [];

    /**
    * Map of special "%n" handling functions, for the debug "format" argument.
    *
    * Valid key names are a single, lower or upper-case letter, i.e. "n" and "N".
    */
    createDebug.formatters = {};

    /**
    * Selects a color for a debug namespace
    * @param {String} namespace The namespace string for the debug instance to be colored
    * @return {Number|String} An ANSI color code for the given namespace
    * @api private
    */
    function selectColor(namespace) {
        let hash = 0;

        for (let i = 0; i < namespace.length; i++) {
            hash = ((hash << 5) - hash) + namespace.charCodeAt(i);
            hash |= 0; // Convert to 32bit integer
        }

        return createDebug.colors[Math.abs(hash) % createDebug.colors.length];
    }
    createDebug.selectColor = selectColor;

    /**
    * Create a debugger with the given `namespace`.
    *
    * @param {String} namespace
    * @return {Function}
    * @api public
    */
    function createDebug(namespace) {
        let prevTime;
        let enableOverride = null;
        let namespacesCache;
        let enabledCache;

        function debug(...args) {
            // Disabled?
            if (!debug.enabled) {
                return;
            }

            const self = debug;

            // Set `diff` timestamp
            const curr = Number(new Date());
            const ms = curr - (prevTime || curr);
            self.diff = ms;
            self.prev = prevTime;
            self.curr = curr;
            prevTime = curr;

            args[0] = createDebug.coerce(args[0]);

            if (typeof args[0] !== 'string') {
                // Anything else let's inspect with %O
                args.unshift('%O');
            }

            // Apply any `formatters` transformations
            let index = 0;
            args[0] = args[0].replace(/%([a-zA-Z%])/g, (match, format) => {
                // If we encounter an escaped % then don't increase the array index
                if (match === '%%') {
                    return '%';
                }
                index++;
                const formatter = createDebug.formatters[format];
                if (typeof formatter === 'function') {
                    const val = args[index];
                    match = formatter.call(self, val);

                    // Now we need to remove `args[index]` since it's inlined in the `format`
                    args.splice(index, 1);
                    index--;
                }
                return match;
            });

            // Apply env-specific formatting (colors, etc.)
            createDebug.formatArgs.call(self, args);

            const logFn = self.log || createDebug.log;
            logFn.apply(self, args);
        }

        debug.namespace = namespace;
        debug.useColors = createDebug.useColors();
        debug.color = createDebug.selectColor(namespace);
        debug.extend = extend;
        debug.destroy = createDebug.destroy; // XXX Temporary. Will be removed in the next major release.

        Object.defineProperty(debug, 'enabled', {
            enumerable: true,
            configurable: false,
            get: () => {
                if (enableOverride !== null) {
                    return enableOverride;
                }
                if (namespacesCache !== createDebug.namespaces) {
                    namespacesCache = createDebug.namespaces;
                    enabledCache = createDebug.enabled(namespace);
                }

                return enabledCache;
            },
            set: v => {
                enableOverride = v;
            }
        });

        // Env-specific initialization logic for debug instances
        if (typeof createDebug.init === 'function') {
            createDebug.init(debug);
        }

        return debug;
    }

    function extend(namespace, delimiter) {
        const newDebug = createDebug(this.namespace + (typeof delimiter === 'undefined' ? ':' : delimiter) + namespace);
        newDebug.log = this.log;
        return newDebug;
    }

    /**
    * Enables a debug mode by namespaces. This can include modes
    * separated by a colon and wildcards.
    *
    * @param {String} namespaces
    * @api public
    */
    function enable(namespaces) {
        createDebug.save(namespaces);
        createDebug.namespaces = namespaces;

        createDebug.names = [];
        createDebug.skips = [];

        let i;
        const split = (typeof namespaces === 'string' ? namespaces : '').split(/[\s,]+/);
        const len = split.length;

        for (i = 0; i < len; i++) {
            if (!split[i]) {
                // ignore empty strings
                continue;
            }

            namespaces = split[i].replace(/\*/g, '.*?');

            if (namespaces[0] === '-') {
                createDebug.skips.push(new RegExp('^' + namespaces.slice(1) + '$'));
            } else {
                createDebug.names.push(new RegExp('^' + namespaces + '$'));
            }
        }
    }

    /**
    * Disable debug output.
    *
    * @return {String} namespaces
    * @api public
    */
    function disable() {
        const namespaces = [
            ...createDebug.names.map(toNamespace),
            ...createDebug.skips.map(toNamespace).map(namespace => '-' + namespace)
        ].join(',');
        createDebug.enable('');
        return namespaces;
    }

    /**
    * Returns true if the given mode name is enabled, false otherwise.
    *
    * @param {String} name
    * @return {Boolean}
    * @api public
    */
    function enabled(name) {
        if (name[name.length - 1] === '*') {
            return true;
        }

        let i;
        let len;

        for (i = 0, len = createDebug.skips.length; i < len; i++) {
            if (createDebug.skips[i].test(name)) {
                return false;
            }
        }

        for (i = 0, len = createDebug.names.length; i < len; i++) {
            if (createDebug.names[i].test(name)) {
                return true;
            }
        }

        return false;
    }

    /**
    * Convert regexp to namespace
    *
    * @param {RegExp} regxep
    * @return {String} namespace
    * @api private
    */
    function toNamespace(regexp) {
        return regexp.toString()
            .substring(2, regexp.toString().length - 2)
            .replace(/\.\*\?$/, '*');
    }

    /**
    * Coerce `val`.
    *
    * @param {Mixed} val
    * @return {Mixed}
    * @api private
    */
    function coerce(val) {
        if (val instanceof Error) {
            return val.stack || val.message;
        }
        return val;
    }

    /**
    * XXX DO NOT USE. This is a temporary stub function.
    * XXX It WILL be removed in the next major release.
    */
    function destroy() {
        console.warn('Instance method `debug.destroy()` is deprecated and no longer does anything. It will be removed in the next major version of `debug`.');
    }

    createDebug.enable(createDebug.load());

    return createDebug;
}

module.exports = setup;