# Copyright (C) 2021 Free Software Foundation, Inc.
#
# This file is part of DejaGnu.
#
# DejaGnu is free software; you can redistribute it and/or modify it
# under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# DejaGnu is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with DejaGnu; if not, write to the Free Software Foundation,
# Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.

# This file was written by Jacob Bachmeyer.

# Procedures for handling specs strings similar to those used in GCC.

# These spec strings support substitutions introduced using "%":
#
#	%%	-- literal "%" character
#	%{...}	-- substitute data value with recursive evaluation
#	%[...]	-- evaluate Tcl code and substitute result literally
#
# All other uses of "%" in specs strings are reserved.  Data item names
# containing colon (":") are generally reserved for future expansion; a few
# are currently used as shorthand for certain DejaGnu API calls.
# Convention for hierarchical name parts is separation using ".", while "/"
# is used for variations intended to be selected using another value.

# Specs are stored in a Tcl array, referred to as the "database" array.
# Spec strings are organized into layers, providing a hierarchical
# structure of fallback and default values by searching layers in the order
# given by the "_layers" option.

# The external data structures used by this module are mostly association
# lists, but they are internally referenced using Tcl arrays.

# All procedures in this module are currently internal to DejaGnu and
# subject to change without notice.
namespace eval ::dejagnu::specs {
    namespace export eval_specs validate_specs
}

# Expand one data substitution token.
# internal procedure; uses SPECS and OPTION arrays in caller's context
proc ::dejagnu::specs::subst_token { key } {
    upvar 1 specs specs option option

    # check for an option first
    if { [info exists option($key)] } {
	return $option($key)
    }

    # check for a board configuration value
    if { [regexp {^board_info\(([^)]+)\):(.*)$} $key -> machine info_key] } {
	return [board_info $machine $info_key]
    }

    # search the specs database if a layer path was given
    if { [info exists option(_layers)] } {
	foreach layer $option(_layers) {
	    if { [info exists specs(layer,$layer,$key)] } {
		return $specs(layer,$layer,$key)
	    }
	}
    }

    # check for suitable default entry in the specs database
    if { [info exists specs(base,$key)] } {
	return $specs(base,$key)
    }

    error "unresolved specs token: $key"
}

# Evaluate excess open or close delimiters.
proc ::dejagnu::specs::delimiter_balance { text } {
    # first, remove all backslashes that cannot quote delimiters
    regsub -all {\\+[^][\\{}]} $text "" text
    # strip backslash-quoted backslashes
    regsub -all {(?:\\{2})+} $text "" text
    # strip backslash-quoted delimiters
    regsub -all {(^|[^\\])\\[][{}]} $text "\\1" text
    # remove all unrelated characters
    regsub -all {[^][{}]+} $text "" text

    # separate the text into only-left and only-right subsets
    regsub -all "\\\\*\[\]\}\]" $text "" left
    regsub -all "\\\\*\[\[\{\]" $text "" right

    return [expr { [string length $left] - [string length $right] }]
}

# Find the end of a token.
proc ::dejagnu::specs::token_end { text start end_pat } {
    set balance 1
    set point $start
    while { $balance > 0 } {
	regexp -indices -start [expr { 1 + $point }] -- $end_pat $text item
	set point [lindex $item 0]
	# optimization: if delimiter_balance returns N, we need at least N
	#     more closing delimiters, but that could be any combination of
	#     braces and brackets, not only the main endpoint delimiter
	for {
	    set balance [delimiter_balance [string range $text $start $point]]
	} { $balance > 1 } { incr balance -1 } {
	    regexp -indices -start [expr { 1 + $point }] -- \
		"\[\\\}\\\]\]" $text item
	    set point [lindex $item 0]
	}
    }
    return [lindex $item 1]
}

# Abstract parsing loop.
# internal procedure; sets TOKEN variable in caller's context
proc ::dejagnu::specs::scan_specs_string { text literal char data code } {
    upvar 1 token token

    for {
	set mark -1
	set point 0
    } { [regexp -indices -start $point -- {%.} $text item] } {
	set point [expr { 1 + $mark }]
    } {
	# extract literal from preceding range
	set token [string range $text \
		       [expr { $mark + 1 }] \
		       [expr { [lindex $item 0] - 1 }]]
	uplevel 1 $literal
	# advance point
	set point [lindex $item 1]
	# extract first character of substitution
	set enter [string index $text $point]
	if { $enter eq "%" } {
	    # %% -- literal "%"
	    set mark $point
	    uplevel 1 $char
	} elseif { $enter eq "\{" } {
	    # %{...} -- substitute data item
	    set mark [token_end $text $point "\\\}"]
	    set token [string range $text \
			   [expr { $point + 1 }] [expr { $mark  - 1 }]]
	    uplevel 1 $data
	} elseif { $enter eq "\[" } {
	    # %[...] -- substitute value from Tcl code fragment
	    set mark [token_end $text $point "\\\]"]
	    set token [string range $text \
			   [expr { $point + 1 }] [expr { $mark  - 1 }]]
	    uplevel 1 $code
	} else {
	    error "unrecognized sequence %$enter in spec string"
	}
    }
    # leave the trailing literal in TOKEN
    set token [string range $text [expr { $mark + 1 }] end]
}

# Generate parse report for specs string; for debugging
proc ::dejagnu::specs::parse_specs_string { text } {
    set tokens [list]
    scan_specs_string $text {
	# intervening literal text
	lappend tokens [list text $token]
    } { # %% escape
	lappend tokens [list text %]
    } { # data item
	lappend tokens [list data $token]
    } { # code item
	lappend tokens [list code $token]
    }
    lappend tokens [list text $token]
    return $tokens
}

# Expand substitutions in specs string.
# internal procedure; uses SPECS and OPTION arrays and BASE_LEVEL variable
# in caller's context
proc ::dejagnu::specs::eval_specs_string { text } {
    upvar 1 specs specs option option base_level base_level

    set output ""
    scan_specs_string $text {
	# copy intervening literal text to output
	append output $token
    } {
	# emit "%" where string contains "%%"
	append output "%"
    } {
	# substitute data item
	append output [eval_specs_string \
			   [subst_token [eval_specs_string $token]]]
    } {
	# evaluate Tcl code fragment
	append output [uplevel "#$base_level" [eval_specs_string $token]]
    }
    # copy trailing literal
    append output $token

    return $output
}

# Check that the provided specs string can be evaluated; that is, that all
# substitutions have definitions.
# internal procedure; uses SPECS and OPTION arrays in caller's context
proc ::dejagnu::specs::validate_specs_string { text } {
    upvar 1 specs specs option option

    scan_specs_string $text {
	# ignore literal text
    } {
	# ignore literal "%"
    } {
	# check substitution
    } {
	# check Tcl code fragment
    }
    # ignore trailing literal

    # an error is thrown if validation fails
    return 1
}

# Perform spec substitutions to evaluate %{GOAL}.
#
#  The DATABASE_NAME is the name (in the caller's context) of the database
#  array to use, while OPTIONS is a list of additional KEY VALUE pairs that
#  should be available for substitution.
proc ::dejagnu::specs::eval_specs { database_name goal options } {
    upvar 1 $database_name specs
    array set option $options
    set base_level [expr { [info level] - 1 }]

    return [eval_specs_string "%{$goal}"]
}

# Load specs strings into DATABASE_NAME; as:
#	load_specs DATABASE_NAME BASE_STRINGS (LAYER_NAME LAYER_STRINGS)...
#  to load only into a layer:
#	load_specs DATABASE_NAME {} LAYER_NAME LAYER_STRINGS
proc ::dejagnu::specs::load_specs { database_name base_strings args } {
    upvar 1 $database_name specs

    if { ([llength $args] & 1) != 0 } {
	error "specs layer names and contents must be in pairs"
    }
    foreach {k v} $base_strings {
	set specs(base,$k) $v
    }
    foreach {layer layer_strings} $args {
	foreach {k v} $layer_strings {
	    set specs(layer,$layer,$k) $v
	}
    }
}

# Display contents of specs database array; for debugging
proc ::dejagnu::specs::dump_specs { database_name } {
    upvar 1 $database_name specs

    set keys [lsort -dictionary [array names specs]]
    # all defaults (base,*) sort ahead of all layers (layer,*,*)

    puts "Specs $database_name:\n"
    for { set i 0 } { ($i < [llength $keys])
		      && [regexp {^base,(.*)$} [lindex $keys $i] \
			      -> name] } \
	{ incr i } {
	    puts "*$name:\n$specs([lindex $keys $i])\n"
	}

    for { set prev "" } { ($i < [llength $keys])
			  && [regexp {^layer,([^,]+),(.*)$} [lindex $keys $i] \
				  -> layer name] } \
	{ incr i } {
	    if { $prev ne $layer } {
		puts "\[$layer\]"
		set prev $layer
	    }
	    puts "*$name:\n$specs([lindex $keys $i])\n"
	}
}

# Validate a specs database
proc ::dejagnu::specs::validate_specs { database_name } {
    upvar 1 $database_name specs

    # TODO
}