class
	CURRENCY_EXCHANGE_HISTORY_COMMAND

inherit
	EL_APPLICATION_COMMAND

	EL_FALLIBLE
		redefine
			reset
		end

	EL_PARSER
		export
			{NONE} all
		redefine
			default_source_text, reset
		end

	EL_STRING_GENERAL_ROUTINES

	TP_FACTORY

	EL_MODULE_EXCEPTION; EL_MODULE_FILE; EL_MODULE_OS; EL_MODULE_LOG

create
	make

feature {EL_COMMAND_CLIENT} -- Initialization

	make (a_output_path: FILE_PATH; a_date_format: STRING)
		local
			date, dec_30_th: EL_DATE; r: REAL; rate_array: SPECIAL [REAL]; year: INTEGER
		do
			output_path := a_output_path; date_format := a_date_format

			make_default

			create parsed
			create currency_code.make_empty
			create base_currency.make_empty
			create exchange_rate_table.make (365)

			html_path_list := OS.file_list (output_path.parent, "*.html")
			if html_path_list.count > 0 and then attached html_path_list.first_path as html_path then
				if attached html_path.base_name.to_string_8.split ('-') as parts and then parts.count > 3 then
					year := parts.last.to_integer
					base_currency := parts [2]
				end
				create dec_30_th.make (year, 12, 30)

				from create date.make (year, 1, 1) until date > dec_30_th loop
					create rate_array.make_filled (r.one, html_path_list.count + 1)
					exchange_rate_table.extend (date.ordered_compact_date, rate_array)
					date.day_forth
				end
				html_path_list.sort (False) -- USD before GBP
			else
				create exchange_rate_table.make_empty
				put_error_message (ZSTRING ("ERROR: no HTML exchange pages found in %S folder.") #$ [output_path.parent])
			end
		end

feature -- Constants

	Description: STRING = "Compile CSV spreadsheet of historical currency exchange rates"

feature -- Basic operations

	execute
		local
			csv_file: PLAIN_TEXT_FILE; i, i_final: INTEGER
		do
			across html_path_list as path until has_error loop
				currency_code := file_currency_code (path.item)
				column_index := path.cursor_index
				parse_html (path.item)
			end
			if has_error then
				print_errors (lio)

			elseif attached exchange_rate_table as table then
				create csv_file.make_open_write (output_path)

				csv_file.put_string ("Column No.,2")
				across html_path_list as list loop
					csv_file.put_character (',')
					csv_file.put_integer (list.cursor_index + 2)
				end
				csv_file.put_new_line

				csv_file.put_string ("," + base_currency + " (1)")
				across html_path_list as list loop
					csv_file.put_character (',')
					csv_file.put_string (file_currency_code (list.item) + " to " + base_currency)
				end
				csv_file.put_new_line

				from table.start until table.after loop
					csv_file.put_string (formatted (table.item_key))

					i_final := table.item_value.count
					from i := 0 until i = i_final loop
						csv_file.put_character (',')
						csv_file.put_real (table.item_value [i])
						i := i + 1
					end
					csv_file.put_new_line
					table.forth
				end
				csv_file.close
			end
		end

feature {NONE} -- Implementation

	default_source_text: STRING
		do
			Result := Empty_string_8
		end

	file_currency_code (html_path: FILE_PATH): STRING
		do
			Result := html_path.base_name.substring_to ('-')
		end

	formatted (compact_date: INTEGER): STRING
		do
			if attached Shared_date as date then
				date.make_by_ordered_compact_date (compact_date)
				Result := date.formatted_out (date_format)
			end
		end

	new_pattern: like all_of
		-- match string like: (01/01/2023)</td><td data-title="Closing Rate">&#36;1 USD = &#8364;0.9343</td>
		do
			Result := all_of (<<
			-- match "(02/01/2022)</td>"
				character_literal ('('),
				natural_number |to| agent on_day,
				character_literal ('/'),
				natural_number |to| agent on_month,
				character_literal ('/'),
				natural_number |to| agent on_year,
				string_literal (")</td>"),

			-- match anything up to " USD = &#8364;"
				while_not_p_match_any (
					all_of (<< string_literal (currency_code + " = &#"), natural_number, character_literal (';') >>)
				),
			-- match 0.8793
				decimal_constant |to| agent on_exchange_rate,
				string_literal ("</td>")
			>>)
			Result.set_action_last (agent on_entry_found)
		end

	parsed_date: INTEGER
		do
			if attached Shared_date as date then
				date.set_date (parsed.year, parsed.month, parsed.day)
				Result := date.ordered_compact_date
			end
		end

	parse_html (html_path: FILE_PATH)
		do
			lio.put_labeled_string ("Data source", html_path.base)
			lio.put_new_line
			lio.put_string ("Parsing ")
			previous_index := 0
			reset_pattern
			set_source_text (File.plain_text (html_path))
			find_all (Void)
			lio.put_line (" OK")
			lio.put_new_line
		end

	reset
		do
			Precursor {EL_FALLIBLE}
			Precursor {EL_PARSER}
		end

feature {NONE} -- Event handlers

	on_day (start_index, end_index: INTEGER)
		do
			parsed.day := integer_32_substring (start_index, end_index)
		end

	on_entry_found (start_index, end_index: INTEGER)
		do
			exchange_rate_table.binary_search (parsed_date)
			if exchange_rate_table.found then
				if exchange_rate_table.index \\ 20 = 0 then
					lio.put_character ('.')
				end
				if previous_index + 1 = exchange_rate_table.index then
					exchange_rate_table.item_value [column_index] := parsed.rate
					previous_index := exchange_rate_table.index
				else
					exchange_rate_table.go_i_th (previous_index + 1)
					Exception.raise_developer ("Missing day %S for %S", [exchange_rate_table.item_key, currency_code])
				end
			end
		end

	on_exchange_rate (start_index, end_index: INTEGER)
		do
			parsed.rate := real_32_substring (start_index, end_index)
		end

	on_month (start_index, end_index: INTEGER)
		do
			parsed.month := integer_32_substring (start_index, end_index)
		end

	on_year (start_index, end_index: INTEGER)
		do
			parsed.year := integer_32_substring (start_index, end_index)
		end

feature {NONE} -- Internal attributes

	base_currency: STRING

	column_index: INTEGER

	currency_code: STRING

	date_format: STRING

	exchange_rate_table: EL_KEY_INDEXED_ARRAYED_MAP_LIST [INTEGER, SPECIAL [REAL]]
		-- cannot use EL_HASH_TABLE because it lacks a routine `go_i_th (index)'

	html_path_list: EL_FILE_PATH_LIST

	output_path: FILE_PATH

	parsed: TUPLE [rate: REAL; year, month, day: INTEGER]

	previous_index: INTEGER

feature {NONE} -- Constants

	Delimiter: STRING = "</a></td></tr>"

	Shared_date: EL_DATE
		once
			create Result.make_now
		end

end