using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Text;

using System.IO;

/// <summary>

/// 提供压缩 JavaScript 代码的能力。

/// </summary>

public sealed class JavaScriptMinifier

{

    #region 私有字段

    private const int EOF = -1;

    private readonly StringBuilder _JsBuilder;

    private readonly TextReader _JsReader;

    private int _TheA = Convert.ToInt32('\n');

    private int _TheB;

    private int _TheLookahead = EOF;

    #endregion

    #region 构造函数

    /// <summary>

    /// 初始化 <see cref="JavaScriptMinifier"/> 类的新实例。

    /// </summary>

    /// <param name="jsReader">包含要压缩的 JavaScript 代码的 <see cref="TextReader"/>。</param>

    private JavaScriptMinifier(TextReader jsReader)

    {

        if (jsReader == null) throw new ArgumentNullException("jsReader");

        this._JsReader = jsReader;

        this._JsBuilder = new StringBuilder();

    }

    #endregion

    #region 静态方法

    /// <summary>

    /// 压缩指定的 JavaScript 代码。

    /// </summary>

    /// <param name="js">包含要压缩的 JavaScript 代码的 <see cref="StringBuilder"/>。</param>

    /// <returns>返回包含压缩后的 JavaScript 代码的 <see cref="StringBuilder"/>。</returns>

    public static StringBuilder Minify(StringBuilder js) { return Minify(new StringReader(js.ToString())); }

    /// <summary>

    /// 压缩指定的 JavaScript 代码。

    /// </summary>

    /// <param name="jsCode">要压缩的 JavaScript 代码。</param>

    /// <returns>返回包含压缩后的 JavaScript 代码的 <see cref="StringBuilder"/>。</returns>

    public static StringBuilder Minify(string jsCode) { return Minify(new StringReader(jsCode)); }

    /// <summary>

    /// 压缩指定的 JavaScript 代码。

    /// </summary>

    /// <param name="jsReader">包含要压缩的 JavaScript 代码的 <see cref="TextReader"/>。</param>

    /// <returns>返回包含压缩后的 JavaScript 代码的 <see cref="StringBuilder"/>。</returns>

    public static StringBuilder Minify(TextReader jsReader)

    {

        JavaScriptMinifier jsmin = new JavaScriptMinifier(jsReader);

        jsmin._Jsmin();

        return jsmin._JsBuilder;

    }

    #endregion

    #region 私有方法

    private void _Jsmin()

    {

        this._Action(3);

        while (this._TheA != EOF)

        {

            switch ((Char)this._TheA)

            {

                case ' ':

                    if (_IsAlphanum(this._TheB)) this._Action(1);

                    else this._Action(2);

                    break;

                case '\n':

                    switch ((Char)this._TheB)

                    {

                        case '{':

                        case '[':

                        case '(':

                        case '+':

                        case '-':

                            this._Action(1);

                            break;

                        case ' ':

                            this._Action(3);

                            break;

                        default:

                            if (_IsAlphanum(this._TheB)) this._Action(1);

                            else this._Action(2);

                            break;

                    }

                    break;

                default:

                    switch ((Char)this._TheB)

                    {

                        case ' ':

                            if (_IsAlphanum(this._TheA))

                            {

                                this._Action(1);

                                break;

                            }

                            this._Action(3);

                            break;

                        case '\n':

                            switch ((Char)this._TheA)

                            {

                                case '}':

                                case ']':

                                case ')':

                                case '+':

                                case '-':

                                case '"':

                                case '\'':

                                    this._Action(1);

                                    break;

                                default:

                                    if (_IsAlphanum(this._TheA)) this._Action(1);

                                    else this._Action(3);

                                    break;

                            }

                            break;

                        default:

                            this._Action(1);

                            break;

                    }

                    break;

            }

        }

    }

    private void _Action(int d)

    {

        if (d <= 1) this._Put(this._TheA);

        if (d <= 2)

        {

            this._TheA = this._TheB;

            if (this._TheA == '\'' || this._TheA == '"')

            {

                for (; ; )

                {

                    this._Put(this._TheA);

                    this._TheA = this._Get();

                    if (this._TheA == this._TheB) break;

                    if (this._TheA <= '\n') throw new Exception(string.Format("Error: JSMIN unterminated string literal: {0}", this._TheA));

                    if (this._TheA != '\\') continue;

                    this._Put(this._TheA);

                    this._TheA = this._Get();

                }

            }

        }

        if (d > 3) return;

        this._TheB = this._Next();

        if (this._TheB != '/' || ((((((((((((this._TheA != '(' && this._TheA != ',') && this._TheA != '=') && this._TheA != '[') && this._TheA != '!') && this._TheA != ':') && this._TheA != '&') && this._TheA != '|') && this._TheA != '?') && this._TheA != '{') && this._TheA != '}') && this._TheA != ';') && this._TheA != '\n')) return;

        this._Put(this._TheA);

        this._Put(this._TheB);

        for (; ; )

        {

            this._TheA = this._Get();

            if (this._TheA == '/') break;

            if (this._TheA == '\\')

            {

                this._Put(this._TheA);

                this._TheA = this._Get();

            }

            else if (this._TheA <= '\n') throw new Exception(string.Format("Error: JSMIN unterminated Regular Expression literal : {0}.", this._TheA));

            this._Put(this._TheA);

        }

        this._TheB = this._Next();

    }

    private int _Next()

    {

        int c = this._Get();

        const int s = (int)'*';

        if (c == '/')

        {

            switch ((Char)this._Peek())

            {

                case '/':

                    for (; ; )

                    {

                        c = this._Get();

                        if (c <= '\n') return c;

                    }

                case '*':

                    this._Get();

                    for (; ; )

                    {

                        switch (this._Get())

                        {

                            case s:

                                if (this._Peek() == '/')

                                {

                                    this._Get();

                                    return Convert.ToInt32(' ');

                                }

                                break;

                            case EOF:

                                throw new Exception("Error: JSMIN Unterminated comment.");

                        }

                    }

                default:

                    return c;

            }

        }

        return c;

    }

    private int _Peek()

    {

        this._TheLookahead = this._Get();

        return this._TheLookahead;

    }

    private int _Get()

    {

        int c = this._TheLookahead;

        this._TheLookahead = EOF;

        if (c == EOF) c = this._JsReader.Read();

        return c >= ' ' || c == '\n' || c == EOF ? c : (c == '\r' ? '\n' : ' ');

    }

    private void _Put(int c) { this._JsBuilder.Append((char)c); }

    private static bool _IsAlphanum(int c) { return ((c >= 'a' && c <= 'z') || (c >= '0' && c <= '9') || (c >= 'A' && c <= 'Z') || c == '_' || c == '$' || c == '\\' || c > 126); }

    #endregion

}