indexing
	description: "Managers that control the data transactions"
	status: "See note at end of class"
	date: "$Date$"
	revision: "$Revision$"

class interface
	TRANSFER_MANAGER

create 

	make
			-- Create manager.

feature -- Access

	has (v: like transaction): BOOLEAN
			-- Does chain include v?
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from CHAIN)
		ensure -- from CONTAINER
			not_found_in_empty: Result implies not is_empty

	index: INTEGER
			-- Index of item, if valid.
			-- (from ARRAYED_LIST)

	index_of (v: like transaction; i: INTEGER): INTEGER
			-- Index of i-th occurrence of item identical to v.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- 0 if none.
			-- (from CHAIN)
		require -- from LINEAR
			positive_occurrences: i > 0
		ensure -- from LINEAR
			non_negative_result: Result >= 0

	transaction: like first
			-- Current item
			-- (from ARRAYED_LIST)
		require -- from  TRANSACTION_CONTAINER
			True
		require -- from TRAVERSABLE
			not_off: not off
		require -- from ACTIVE
			readable: readable
		require else -- from ARRAYED_LIST
			index_is_valid: valid_index (index)

	source: DATA_RESOURCE
			-- Selected source

	target: DATA_RESOURCE
			-- Selected target
	
feature -- Measurement

	count: INTEGER
			-- Number of items.
			-- (from ARRAYED_LIST)

	finished_transactions: INTEGER
			-- Number of already finished transactions

	occurrences (v: like transaction): INTEGER
			-- Number of times v appears.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from CHAIN)
		ensure -- from BAG
			non_negative_occurrences: Result >= 0

	occurrences (v: like transaction): INTEGER
			-- Number of times v appears.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from CHAIN)
		ensure -- from BAG
			non_negative_occurrences: Result >= 0

	total_count: INTEGER
			-- Total number of transactions
		ensure
			index_unchanged: index = old index
	
feature -- Comparison

	is_equal (other: like Current): BOOLEAN
			-- Does other contain the same elements?
			-- (from LIST)
		require -- from ANY
			other_not_void: other /= void
		ensure -- from ANY
			symmetric: Result implies other.is_equal (Current)
			consistent: standard_is_equal (other) implies Result
		ensure then -- from LIST
			indices_unchanged: index = old index and other.index = old other.index
			true_implies_same_size: Result implies count = other.count
	
feature -- Status report

	after: BOOLEAN
			-- Is there no valid cursor position to the right of cursor?
			-- (from LIST)

	before: BOOLEAN
			-- Is there no valid cursor position to the left of cursor?
			-- (from LIST)

	changeable_comparison_criterion: BOOLEAN
			-- May object_comparison be changed?
			-- (Answer: yes by default.)
			-- (from CONTAINER)

	error: BOOLEAN
			-- Has an error occurred in any transaction?
		require
			not_empty: not is_empty

	error_reason: STRING
			-- Reason of most recent error
		require
			error_exists: error
		ensure
			non_empty_string: Result /= void and then not Result.is_empty
			index_unchanged: index = old index

	error_stops: BOOLEAN
			-- Is transfer stopped on error?
			-- (from TRANSACTION_CONTAINER)

	exhausted: BOOLEAN
			-- Has structure been completely explored?
			-- (from LINEAR)
		ensure -- from LINEAR
			exhausted_when_off: off implies Result

	Extendible: BOOLEAN is True
			-- May new items be added? (Answer: yes.)
			-- (from DYNAMIC_CHAIN)

	full: BOOLEAN
			-- Is structure filled to capacity?
			-- (from ARRAYED_LIST)

	insertable (t: TRANSACTION): BOOLEAN
			-- Can transaction t be added?
		require -- from TRANSACTION_CONTAINER
			transaction_exists: t /= void

	is_empty: BOOLEAN
			-- Is structure empty?
			-- (from FINITE)

	is_inserted (v: TRANSACTION): BOOLEAN
			-- Has v been inserted at the end by the most recent put or
			-- extend?
			-- (from ARRAYED_LIST)

	object_comparison: BOOLEAN
			-- Must search operations use equal rather than =
			-- for comparing references? (Default: no, use =.)
			-- (from CONTAINER)

	off: BOOLEAN
			-- Is there no current item?
			-- (from CHAIN)

	prunable: BOOLEAN
			-- May items be removed? (Answer: yes.)
			-- (from ARRAYED_LIST)

	readable: BOOLEAN
			-- Is there a current item that may be read?
			-- (from SEQUENCE)

	transactions_succeeded: BOOLEAN
			-- Have all transactions succeeded?
		require
			not_empty: not is_empty

	transfer_finished: BOOLEAN
			-- Has a transfer taken place?

	writable: BOOLEAN
			-- Is there a current item that may be modified?
			-- (from SEQUENCE)
	
feature -- Status setting

	compare_objects
			-- Ensure that future search operations will use equal
			-- rather than = for comparing references.
			-- (from CONTAINER)
		require -- from CONTAINER
			changeable_comparison_criterion
		ensure -- from CONTAINER
			object_comparison

	compare_references
			-- Ensure that future search operations will use =
			-- rather than equal for comparing references.
			-- (from CONTAINER)
		require -- from CONTAINER
			changeable_comparison_criterion
		ensure -- from CONTAINER
			reference_comparison: not object_comparison

	continue_on_error
			-- Error does not stop action.
			-- (from TRANSACTION_CONTAINER)
		ensure -- from TRANSACTION_CONTAINER
			does_not_stop: not error_stops

	reset_status
			-- Reset status flags.
		ensure
			finished_flag_reset: not transfer_finished
			no_error: not error

	stop_on_error
			-- Error stops action.
			-- (from TRANSACTION_CONTAINER)
		ensure -- from TRANSACTION_CONTAINER
			stop: error_stops
	
feature -- Cursor movement

	back
			-- Move cursor one position backward.
			-- (from ARRAYED_LIST)
		require -- from BILINEAR
			not_before: not before

	finish
			-- Move cursor to last position if any.
			-- (from ARRAYED_LIST)
		ensure then -- from CHAIN
			at_last: not is_empty implies islast
		ensure then -- from ARRAYED_LIST
			before_when_empty: is_empty implies before

	forth
			-- Move cursor one position forward.
			-- (from ARRAYED_LIST)
		require -- from LINEAR
			not_after: not after
		ensure then -- from LIST
			moved_forth: index = old index + 1

	select_transaction (i: INTEGER)
			-- Move cursor to i-th position.
			-- (from ARRAYED_LIST)
		require -- from CHAIN
			valid_cursor_index: valid_cursor_index (i)
		require -- from TRANSACTION_CONTAINER
			not_empty: not is_empty
			index_in_range: 1 <= n and n <= count
		ensure -- from CHAIN
			position_expected: index = i
		ensure -- from TRANSACTION_CONTAINER
			selected: index = n

	search (v: like transaction)
			-- Move to first position (at or after current
			-- position) where item and v are equal.
			-- If structure does not include v ensure that
			-- exhausted will be true.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from BILINEAR)
		ensure -- from LINEAR
			object_found: (not exhausted and object_comparison) implies equal (v, transaction)
			item_found: (not exhausted and not object_comparison) implies v = transaction

	start
			-- Move cursor to first position if any.
			-- (from ARRAYED_LIST)
		ensure then -- from CHAIN
			at_first: not is_empty implies isfirst
		ensure then -- from ARRAYED_LIST
			after_when_empty: is_empty implies after
	
feature -- Element change

	add_transaction (t: TRANSACTION)
			-- Add transaction.
			-- (from TRANSACTION_CONTAINER)
		require -- from TRANSACTION_CONTAINER
			transaction_exists: t /= void
			transaction_correct: t.is_correct
		ensure -- from TRANSACTION_CONTAINER
			one_more_item: count = old count + 1
			index_unchanged: not old is_empty implies index = old index

	append (s: SEQUENCE [TRANSACTION])
			-- Append a copy of s.
			-- (from SEQUENCE)
		require -- from SEQUENCE
			argument_not_void: s /= void
		ensure -- from SEQUENCE
			new_count: count >= old count

	extend (v: like transaction)
			-- Add v to end.
			-- Do not move cursor.
			-- Was declared in ARRAYED_LIST as synonym of force.
			-- (from ARRAYED_LIST)
		require -- from COLLECTION
			extendible: extendible
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		ensure then -- from BAG
			one_more_occurrence: occurrences (v) = old (occurrences (v)) + 1

	fill (other: CONTAINER [TRANSACTION])
			-- Fill with as many items of other as possible.
			-- The representations of other and current structure
			-- need not be the same.
			-- (from COLLECTION)
		require -- from COLLECTION
			other_not_void: other /= void
			extendible

	force (v: like transaction)
			-- Add v to end.
			-- Do not move cursor.
			-- Was declared in ARRAYED_LIST as synonym of extend.
			-- (from ARRAYED_LIST)
		require -- from SEQUENCE
			extendible: extendible
		ensure then -- from SEQUENCE
			new_count: count = old count + 1
			item_inserted: has (v)

	put (v: like transaction)
			-- Replace current item by v.
			-- (Synonym for replace)
			-- (from CHAIN)
		require -- from COLLECTION
			extendible: extendible
		ensure -- from COLLECTION
			item_inserted: is_inserted (v)
		ensure then -- from CHAIN
			same_count: count = old count
		ensure then -- from SEQUENCE
			new_count: count = old count + 1

	replace (v: like first)
			-- Replace current item by v.
			-- (from ARRAYED_LIST)
		require -- from ACTIVE
			writable: writable
		ensure -- from ACTIVE
			item_replaced: transaction = v
	
feature -- Removal

	prune (v: like transaction)
			-- Remove first occurrence of v, if any,
			-- after cursor position.
			-- Move cursor to right neighbor.
			-- (or after if no right neighbor or v does not occur)
			-- (from ARRAYED_LIST)
		require -- from COLLECTION
			prunable: prunable

	prune_all (v: like transaction)
			-- Remove all occurrences of v.
			-- (Reference or object equality,
			-- based on object_comparison.)
			-- (from ARRAYED_LIST)
		require -- from COLLECTION
			prunable
		ensure -- from COLLECTION
			no_more_occurrences: not has (v)
		ensure then -- from DYNAMIC_CHAIN
			is_exhausted: exhausted
		ensure then -- from ARRAYED_LIST
			is_after: after

	remove
			-- Remove current item.
			-- Move cursor to right neighbor
			-- (or after if no right neighbor)
			-- (from ARRAYED_LIST)
		require -- from ACTIVE
			prunable: prunable
			writable: writable
		ensure then -- from DYNAMIC_LIST
			after_when_empty: is_empty implies after
		ensure then -- from ARRAYED_LIST
			index: index = old index

	remove_transaction (n: INTEGER)
			-- Remove n-th transaction.
		require
			not_empty: not is_empty
			index_in_range: 1 <= n and n <= count
		ensure
			one_less_item: count = count - 1
			index_unchanged: (old index < old count) implies (index = old index)
			index_adapted: (old index = old count) implies (index = old index - 1)

	wipe_out
			-- Remove all items.
			-- (from ARRAYED_LIST)
		require -- from COLLECTION
			prunable
		ensure -- from COLLECTION
			wiped_out: is_empty
		ensure then -- from DYNAMIC_LIST
			is_before: before
	
feature -- Conversion

	linear_representation: LINEAR [TRANSACTION]
			-- Representation as a linear structure
			-- (from LINEAR)
	
feature -- Duplication

	copy (other: like Current)
			-- Reinitialize by copying all the items of other.
			-- (This is also used by clone.)
			-- (from ARRAY)
		require -- from ANY
			other_not_void: other /= void
			type_identity: same_type (other)
		ensure -- from ANY
			is_equal: is_equal (other)
		ensure then -- from ARRAY
			equal_areas: area.is_equal (other.area)
	
feature -- Basic operations

	execute_transaction
			-- Execute selected transaction.
		ensure
			counter_updated: not transaction.error implies finished_transactions = old finished_transactions + transaction.count

	transfer
			-- Transfer file.
		require
			not_empty: not is_empty
			flags_reset: not (transfer_finished and transactions_succeeded)
		ensure
			transfer_flag_set: transfer_finished
	
feature -- Iteration

	do_all (action: PROCEDURE [ANY, TUPLE [TRANSACTION]])
			-- Apply action to every item.
			-- Semantics not guaranteed if action changes the structure;
			-- in such a case, apply iterator to clone of structure instead.
			-- (from LINEAR)
		require -- from TRAVERSABLE
			action_exists: action /= void

	do_if (action: PROCEDURE [ANY, TUPLE [TRANSACTION]]; test: FUNCTION [ANY, TUPLE [TRANSACTION], BOOLEAN])
			-- Apply action to every item that satisfies test.
			-- Semantics not guaranteed if action or test changes the structure;
			-- in such a case, apply iterator to clone of structure instead.
			-- (from LINEAR)
		require -- from TRAVERSABLE
			action_exists: action /= void
			test_exits: test /= void

	for_all (test: FUNCTION [ANY, TUPLE [TRANSACTION], BOOLEAN]): BOOLEAN
			-- Is test true for all items?
			-- (from LINEAR)
		require -- from TRAVERSABLE
			test_exits: test /= void

	there_exists (test: FUNCTION [ANY, TUPLE [TRANSACTION], BOOLEAN]): BOOLEAN
			-- Is test true for at least one item?
			-- (from LINEAR)
		require -- from TRAVERSABLE
			test_exits: test /= void
	
invariant

	finished_transaction_range: 0 <= finished_transactions and finished_transactions <= total_count
		-- from ANY
	reflexive_equality: standard_is_equal (Current)
	reflexive_conformance: conforms_to (Current)
		-- from TRANSACTION_CONTAINER
	empty_definition: is_empty = (count = 0)
	index_in_range: not is_empty implies (1 <= index and index <= count)
		-- from ACTIVE
	writable_constraint: writable implies readable
	empty_constraint: is_empty implies (not readable) and (not writable)
		-- from BILINEAR
	not_both: not (after and before)
	before_constraint: before implies off
		-- from LINEAR
	after_constraint: after implies off
		-- from TRAVERSABLE
	empty_constraint: is_empty implies off
		-- from FINITE
	empty_definition: is_empty = (count = 0)
	non_negative_count: count >= 0
		-- from ARRAYED_LIST
	prunable: prunable
	starts_from_one: lower = 1
	empty_means_storage_empty: is_empty implies all_default
		-- from ARRAY
	area_exists: area /= void
	consistent_size: capacity = upper - lower + 1
	non_negative_count: count >= 0
	index_set_has_same_count: valid_index_set
		-- from RESIZABLE
	increase_by_at_least_one: minimal_increase >= 1
		-- from BOUNDED
	valid_count: count <= capacity
	full_definition: full = (count = capacity)
		-- from INDEXABLE
	index_set_not_void: index_set /= void
		-- from LIST
	before_definition: before = (index = 0)
	after_definition: after = (index = count + 1)
		-- from CHAIN
	non_negative_index: index >= 0
	index_small_enough: index <= count + 1
	off_definition: off = ((index = 0) or (index = count + 1))
	isfirst_definition: isfirst = ((not is_empty) and (index = 1))
	islast_definition: islast = ((not is_empty) and (index = count))
	item_corresponds_to_index: (not off) implies (transaction = i_th (index))
	index_set_has_same_count: index_set.count = count
		-- from DYNAMIC_CHAIN
	extendible: extendible

end -- class TRANSFER_MANAGER