# tclrivetparser.tcl -- parse Rivet files in pure Tcl.

# Copyright 2003-2004 The Apache Software Foundation

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at

#	http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

package provide tclrivetparser 0.1

namespace eval tclrivetparser {
    set starttag <?
    set endtag   ?>
    set outputcmd {puts -nonewline}
    namespace export parserivetdata
}

# tclrivetparser::setoutputcmd --
#
#	Set the output command used.  In regular Rivet scripts, we use
#	puts, but that might not be ideal if you want to parse Rivet
#	pages in a Tcl script.
#
# Arguments:
#	newcmd - if empty, return the current command, if not, set the
#	command.
#
# Side Effects:
#	May set the output command used.
#
# Results:
#	The current output command.

proc tclrivetparser::setoutputcmd { {newcmd ""} } {
    variable outputcmd

    if { $outputcmd == "" } {
	    return $outputcmd
    }
    set outputcmd $newcmd
}

# tclrivetparser::parse --
#
#	Parse a buffer, transforming <? and ?> into the appropriate
#	Tcl strings.  Note that initial 'puts "' is not performed
#	here.
#
# Arguments:
#	data - data to scan.
#	outbufvar - name of the output buffer.
#
# Side Effects:
#	None.
#
# Results:
#	Returns the $inside variable - 1 if we are inside a <? ?>
#	section, 0 if we outside.

proc tclrivetparser::parse { data outbufvar } {
    variable outputcmd
    variable starttag
    variable endtag
    set inside      0
    set shorthand   0

    upvar $outbufvar outbuf

    set i 0
    set p 0
    set len [expr {[string length $data] + 1}]
    set next [string index $data 0]
    while {$i < $len} {
        incr i
        set cur $next
        set next [string index $data $i]
        if { $inside == 0 } {
            # Outside the delimiting tags.
            if { $cur == [string index $starttag $p] } {
                incr p
                if { $p == [string length $starttag] } {

                    if {$next == "="} {
#                       puts stderr "shorthand begin detected"
                        append outbuf "\"\n $outputcmd "
                        set shorthand   1
                        incr i
                        set next [string index $data $i]
                    } else {
                        append outbuf "\"\n"
                    }

                    set inside 1
                    set p 0
                    continue
                }
            } else {
                if { $p > 0 } {
                    append outbuf [string range $starttag 0 [expr {$p - 1}]]
                    set p 0
                }
                switch -exact -- $cur {
                    "\{" {
                        append outbuf \ $cur
                    }
                    "\}" {
                        append outbuf \ $cur 
                    }
                    "\$" {
                        append outbuf "\\$"
                    }
                    "\[" {
                        append outbuf "\\["
                    }
                    "\]" {
                        append outbuf "\\]"
                    }
                    "\"" {
                        append outbuf "\\\""
                    }
                    "\\" {
                        append outbuf "\\\\"
                    }
                    default {
                        append outbuf $cur
                    }
                }
                continue
            }
        } else {
            # Inside the delimiting tags.
            if { $cur == [string index $endtag $p] } {
                incr p
                if { $p == [string length $endtag] } {
                    if {$shorthand} {
#                       puts stderr "shorthand end detected"
                        set shorthand 0
                    } 
                    append outbuf "\n$outputcmd \""
                    set inside 0
                    set p 0
                }
            } else {
                if { $p > 0 } {
                    append outbuf [string range $endtag 0 $p]
                    set p 0
                }
                append outbuf $cur
            }
        }
    }
    return $inside
}


# tclrivetparser::parserivetdata --
#
#	Parse a rivet script, and add the relavant opening and closing
#	bits.
#
# Arguments:
#	data - data to parse.
#
# Side Effects:
#	None.
#
# Results:
#	Returns the parsed script.

proc tclrivetparser::parserivetdata { data } {
    variable outputcmd
    set outbuf {}
    append outbuf "$outputcmd \""
    if { [parse $data outbuf] == 0 } {
        append outbuf "\"\n"
    }
    return $outbuf
}