/*******************************************************************************

        Copyright:
            Copyright (c) 2004 Kris Bell.
            Some parts copyright (c) 2009-2016 dunnhumby Germany GmbH.
            All rights reserved.

        License:
            Tango Dual License: 3-Clause BSD License / Academic Free License v3.0.
            See LICENSE_TANGO.txt for details.

        Version: Initial release: April 2004

        Authors: Kris, John Reimer

*******************************************************************************/

module ocean.net.http.HttpStack;

import ocean.core.ExceptionDefinitions;
import ocean.meta.types.Qualifiers;

import core.stdc.string: memmove;
import core.stdc.stdio;
import core.sys.posix.strings: strncasecmp;

/******************************************************************************

        Internal representation of a token

******************************************************************************/

class Token
{
    private cstring value;

    Token set (cstring value)
    {
        this.value = value;
        return this;
    }

    cstring get()
    {
        return this.value;
    }

    // disabled because to work in D2 this requires
    // hidden allocation
    override istring toString ()
    {
        printf(("Use Token.get instead of Token.toString :" ~
                " latter allocates each time. Aborting\n").ptr);
        assert(0);
    }
}

/******************************************************************************

        A stack of Tokens, used for capturing http headers. The tokens
        themselves are typically mapped onto the content of a Buffer,
        or some other external content, so there's minimal allocation
        involved (typically zero).

******************************************************************************/

class HttpStack
{
        private int     depth;
        private Token[] tokens;

        private static immutable int MaxHttpStackSize = 256;

        /**********************************************************************

                Construct a HttpStack with the specified initial size.
                The stack will later be resized as necessary.

        **********************************************************************/

        this (int size = 10)
        {
                tokens = new Token[0];
                resize (tokens, size);
        }

        /**********************************************************************

                Clone this stack of tokens

        **********************************************************************/

        HttpStack clone ()
        {
                // setup a new HttpStack of the same depth
                HttpStack clone = new HttpStack(depth);

                clone.depth = depth;

                // duplicate the content of each original token
                for (int i=0; i < depth; ++i)
                     clone.tokens[i].set (tokens[i].get().dup);

                return clone;
        }

        /**********************************************************************

                Iterate over all tokens in stack

        **********************************************************************/

        int opApply (scope int delegate(ref Token) dg)
        {
                int result = 0;

                for (int i=0; i < depth; ++i)
                     if ((result = dg (tokens[i])) != 0)
                          break;
                return result;
        }

        /**********************************************************************

                Pop the stack all the way back to zero

        **********************************************************************/

        final void reset ()
        {
                depth = 0;
        }

        /**********************************************************************

                Scan the tokens looking for the first one with a matching
                name. Returns the matching Token, or null if there is no
                such match.

        **********************************************************************/

        final Token findToken (cstring match)
        {
                Token tok;

                for (int i=0; i < depth; ++i)
                    {
                    tok = tokens[i];
                    if (isMatch (tok, match))
                        return tok;
                    }
                return null;
        }

        /**********************************************************************

                Scan the tokens looking for the first one with a matching
                name, and remove it. Returns true if a match was found, or
                false if not.

        **********************************************************************/

        final bool removeToken (cstring match)
        {
                for (int i=0; i < depth; ++i)
                     if (isMatch (tokens[i], match))
                        {
                        tokens[i].value = null;
                        return true;
                        }
                return false;
        }

        /**********************************************************************

                Return the current stack depth

        **********************************************************************/

        final int size ()
        {
                return depth;
        }

        /**********************************************************************

                Push a new token onto the stack, and set it content to
                that provided. Returns the new Token.

        **********************************************************************/

        final Token push (cstring content)
        {
                return push().set (content);
        }

        /**********************************************************************

                Push a new token onto the stack, and set it content to
                be that of the specified token. Returns the new Token.

        **********************************************************************/

        final Token push (ref Token token)
        {
                return push (token.get());
        }

        /**********************************************************************

                Push a new token onto the stack, and return it.

        **********************************************************************/

        final Token push ()
        {
                if (depth == tokens.length)
                    resize (tokens, depth * 2);
                return tokens[depth++];
        }

        /**********************************************************************

                Pop the stack by one.

        **********************************************************************/

        final void pop ()
        {
                if (depth)
                    --depth;
                else
                   throw new IOException ("illegal attempt to pop Token stack");
        }

        /**********************************************************************

                See if the given token matches the specified text. The
                two must match the minimal extent exactly.

        **********************************************************************/

        final static bool isMatch (ref Token token, cstring match)
        {
                auto target = token.get();

                auto length = target.length;
                if (length > match.length)
                    length = match.length;

                if (length is 0)
                    return false;

                return strncasecmp (target.ptr, match.ptr, length) is 0;
        }

        /**********************************************************************

                Resize this stack by extending the array.

        **********************************************************************/

        final static void resize (ref Token[] tokens, int size)
        {
                auto i = tokens.length;

                // this should *never* realistically happen
                if (size > MaxHttpStackSize)
                    throw new IOException ("Token stack exceeds maximum depth");

                for (tokens.length=size; i < tokens.length; ++i)
                     tokens[i] = new Token();
        }
}