note
	description: "[
		Helper to perform efficient search of a string in another one.
		Note: The algorithm used is the one described in Communications of the ACM,
			volume 33, number 8, August 1990, by Daniel M. Sunday. The fuzzy
			version was presented by Peter R. Sibbald in Communications of the
			ACM, volume 35, number 4, April 1992 (Technical Correspondance).
	]"
	library: "Free implementation of ELKS library"
	status: "See notice at end of class."
	legal: "See notice at end of class."
	date: "$Date: 2012-05-24 04:13:10 +0000 (Thu, 24 May 2012) $"
	revision: "$Revision: 91981 $"

deferred class interface
	STRING_SEARCHER

feature -- Initialization

	initialize_deltas (a_pattern: READABLE_STRING_GENERAL)
			-- Initialize deltas with a_pattern.
			-- Optimized for the top max_code_point_value characters only.
		require
			a_pattern_not_void: a_pattern /= Void
	
feature -- Access

	string_type: READABLE_STRING_GENERAL
			-- Type of strings Current manipulate to perform searches.
		ensure
			for_typing_only: False

	max_code_point_value: INTEGER_32
			-- Maximum character value for which we optimize the lookup of a pattern.
			-- If any item's code of the searched string is above that limit, search will
			-- not be as efficient.
		ensure
			positive: Result > 0
	
feature -- Search

	substring_index (a_string: like string_type; a_pattern: READABLE_STRING_GENERAL; start_pos, end_pos: INTEGER_32): INTEGER_32
			-- Position of first occurrence of a_pattern at or after start_pos
			-- and before end_pos in a_string.
			-- 0 if there are no matches.
		require
			a_string_not_void: a_string /= Void
			a_pattern_not_void: a_pattern /= Void
			start_large_enough: start_pos >= 1
			end_pos_large_enough: start_pos <= end_pos + 1
			end_pos_small_enough: end_pos <= a_string.count

	substring_index_with_deltas (a_string: like string_type; a_pattern: READABLE_STRING_GENERAL; start_pos, end_pos: INTEGER_32): INTEGER_32
			-- Position of first occurrence of a_pattern at or after start_pos in a_string.
			-- 0 if there are no matches.
		require
			a_string_not_void: a_string /= Void
			a_pattern_not_void: a_pattern /= Void
			a_pattern_not_empty: not a_pattern.is_empty
			start_large_enough: start_pos >= 1
			end_pos_large_enough: start_pos <= end_pos + 1
			end_pos_small_enough: end_pos <= a_string.count

	substring_index_list_with_deltas (a_string: like string_type; a_pattern: READABLE_STRING_GENERAL; start_pos, end_pos: INTEGER_32): detachable ARRAYED_LIST [INTEGER_32]
			-- Index positions of all occurrences of a_pattern at or after start_pos until end_pos in a_string.
			-- Result is Void if there are no matches.
		require
			a_string_not_void: a_string /= Void
			a_pattern_not_void: a_pattern /= Void
			a_pattern_not_empty: not a_pattern.is_empty
			start_large_enough: start_pos >= 1
			end_pos_large_enough: start_pos <= end_pos + 1
			end_pos_small_enough: end_pos <= a_string.count
		ensure
			matches: Result /= Void implies not Result.is_empty

	fuzzy_index (a_string: like string_type; a_pattern: READABLE_STRING_GENERAL; start_pos, end_pos, fuzzy: INTEGER_32): INTEGER_32
			-- Position of first occurrence of a_pattern at or after start_pos in
			-- a_string with 0..fuzzy mismatches between a_string and a_pattern.
			-- 0 if there are no fuzzy matches.
		require
			a_string_not_void: a_string /= Void
			a_pattern_not_void: a_pattern /= Void
			a_pattern_not_empty: not a_pattern.is_empty
			start_large_enough: start_pos >= 1
			end_pos_large_enough: start_pos <= end_pos + 1
			end_pos_small_enough: end_pos <= a_string.count
			fuzzy_non_negative: fuzzy >= 0
			acceptable_fuzzy: fuzzy <= a_pattern.count
	
invariant
	deltas_not_void: deltas /= Void
	deltas_valid: deltas.capacity = max_code_point_value + 1

note
	copyright: "Copyright (c) 1984-2012, Eiffel Software and others"
	license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)"
	source: "[
		Eiffel Software
		5949 Hollister Ave., Goleta, CA 93117 USA
		Telephone 805-685-1006, Fax 805-685-6869
		Website http://www.eiffel.com
		Customer support http://support.eiffel.com
	]"

end -- class STRING_SEARCHER

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