Module:CsvUtils

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Overview

The CsvUtils module loads, processes, and returns data that is stored in CSV format in wiki templates. This module also provides a parsing method to convert well-structured CSV data into a Lua table.

Requirements

The CSV data must be well structured. The header row cannot have empty names, and all lines must end with a comma.

There can be documentation in the template, and this module will automatically remove it, provided it is enclosed in a <noinclude> block. The CSV data itself must be wrapped in a <pre> block in order to protect line breaks. The <pre> block will also be removed.

Usage

The standard way of using this module is a call like the following: 

dataTable, headerLookupTable = CsvUtils.extractTables(DATA_TEMPLATE_NAME)

This is a shortcut method for the other two: extractCSV and luaTableFromCSV. The extractCSV method loads the template and removes all surrounding documentation. It returns a very long string of CSV data, including newlines. The luaTableFromCSV method takes that string and parses it, splitting it into a header row and data rows, and each row into fields. It returns the data itself and a lookup table with header names, allowing constant time lookup of indexes in the data table from string names of the headers. In other words, if you know the column has the header "constructionTime", then if the data at index 10 stores the value for constructionTime, 45s: 

headerLookupTable"constructionTime" = 10
dataTable10 = 45

The data table has the following structure: 

dataTable = {
   [1] = { 
        [1] = "header1Name",
        [2] = "header2Name",
        [3] = "header3Name",
        ...
    },
    [2] = {
        [1] = {
            dataRow1field1,
            dataRow1field2,
            dataRow1field3,
            ...
        },
        [2] = {
            dataRow2field1,
            ...
        },
        [3] = {
            dataRow3field1,
            ...
        },
        ...
    }
}

The header lookup table has the following structure: 

headerLookupTable = {
    "header1Name" = 1,
    "header2Name" = 2,
    "header3Name" = 3,
    ...
}

---
--- The CsvUtils module loads, processes, and returns data that is stored in CSV
--- format in wiki templates.
---
--- There can be documentation in the template, and this module will
--- automatically remove it, provided it is enclosed in a <noinclude> block. The
--- CSV data itself must be wrapped in a <pre> block in order to protect line
--- breaks. The <pre> block will also be removed. This module also provides a
--- parsing method to convert well-structured CSV data into a Lua table.
---
--- The CSV data must be well structured. The header row cannot have empty names,
--- and all lines must end with a comma.
---
--- The standard way of using this module is a call like the following:
---
--- dataTable, headerLookupTable = CsvUtils.extractTables(DATA_TEMPLATE_NAME)
---
--- This is a shortcut method for the other two: extractCSV and luaTableFromCSV.
--- The extractCSV method loads the template and removes all surrounding
--- documentation. It returns a very long string of CSV data, including newlines.
--- The luaTableFromCSV method takes that string and parses it, splitting it
--- into a header row and data rows, and each row into fields. It returns the
--- data itself and a lookup table with header names, allowing constant time
--- lookup of indexes in the data table from string names of the headers. In
--- other words, if you know the column has the header "constructionTime", then
--- if the data at index 10 stores the value for constructionTime, 45s:
---
--- headerLookupTable["constructionTime"] = 10
--- dataTable[10] = 45
---
--- The data table has the following structure:
---
--- dataTable = {
--- 	[1] = {
--- 		[1] = "header1Name",
--- 		[2] = "header2Name",
--- 		[3] = "header3Name",
---			...
---		},
--- 	[2] = {
---			[1] = {
---				dataRow1field1,
---				dataRow1field2,
---				dataRow1field3,
---				...
--- 		},
---			[2] = {
---				dataRow2field1,
---				...
---			},
---			[3] = {
---				dataRow3field1,
---				...
---			},
---			...
---		}
--- }
---
--- The header lookup table has the following structure:
---
--- headerLookupTable = {
---		["header1Name"] = 1,
---		["header2Name"] = 2,
---		["header3Name"] = 3,
---		...
--- }
---
--- @module CsvUtils
local CsvUtils = {}



--region Private constants

local HTML_ENTITY_NEWLINE = "&#10;"
local HTML_ENTITY_COMMA = "&comma;"
local HTML_ENTITY_QUOTES = "&quot;"

--endregion



--region Private methods

---
--- Replaces newlines and commas between quotation marks with their HTML codes,
--- so that they aren't interpreted as newlines that separate records in the csv
--- data string.
---
--- @param stringToEncode string input to be processed.
--- @return string modified with special characters replaced.
local function encodeQuotations(stringToEncode)

	-- Sub out newlines with their HTML character code
	local encodedString = stringToEncode:gsub('[\r\n]+', HTML_ENTITY_NEWLINE)
	if encodedString == "" then
		error("Encoding newlines inside quoted descriptions resulted in no data left.")
	end

	-- Sub out commas within the matched quotation
	encodedString = encodedString:gsub(",", HTML_ENTITY_COMMA)
	if encodedString == "" then
		error("Encoding commas inside quoted descriptions resulted in no data left.")
	end

	return encodedString
end



---
--- Replaces apostrophes and double quotes in a string with their respective
--- HTML character codes.
---
--- @param stringToEncode string to be processed.
--- @return string modified with special characters replaced.
local function encodeCSV(stringToEncode)

	-- Call a function on quotations to replace newlines within them. Capture
	-- the entire quote, including the bounding quotation marks.
	local encodedString = stringToEncode:gsub("(\".-\")", encodeQuotations)

	-- Now that quotations are handled, sub double quotes for their HTML code.
	encodedString = encodedString:gsub("\"", HTML_ENTITY_QUOTES)
	if encodedString == "" then
		error("Encoding double quotation marks resulted in no data left.")
	end

	return encodedString
end

--endregion



--region Public methods

---
--- Shortcut method for the two main methods of this module.
---
--- @param dataPageName string name of the template page containing the CSV data, including the namespace, like this: "Template:Workshops_Recipes_csv"
--- @return table of data from CSV
--- @return table of header names for looking up indexes for the data table
function CsvUtils.extractTables(dataPageName)
	
	return CsvUtils.luaTableFromCSV(CsvUtils.extractCSV(dataPageName))
end



---
--- Loads the data from a wiki template page, removing all surrounding
--- documentation.
---
--- Throws an error if the page could not be loaded or if there was a problem
--- processing the page content, so that invoking methods can debug. (This
--- should never cause an error at runtime.)
---
--- @param dataPageName string name of the template page containing the CSV data, including the namespace, like this: "Template:Workshops_Recipes_csv"
--- @return table raw CSV data
function CsvUtils.extractCSV(dataPageName)
	
	-- Load the page and verify something returned correctly. If the page was 
	-- not found, then the page will be nil or the site will tell us that the
	-- page doesn't exist.
    local csvPage = mw.title.new(dataPageName)
    if not csvPage or not csvPage.exists then
        error("Site could not find data page: " .. dataPageName)
    end
    
	-- Get the content of the page, or it will be nil if there is no page. We
	-- can also expect there's a problem if there's an empty string.
    local pageContent = csvPage:getContent()
	if not pageContent or pageContent == "" then
		error("Content does not exist on data page: " .. dataPageName)
	end
	
	-- Remove everything within and including the <noinclude> tags. If this
	-- results in an empty string, there was a problem.
	-- Since we're still dealing with mediawiki content, use MW library instead
	-- of Lua string library.
	local trimmedText = mw.ustring.gsub(pageContent, "<noinclude>.-</noinclude>", "")
	if trimmedText == "" then
		error("Trimming content resulted in no data left on data page: " .. dataPageName)
	end
    
    -- Extract the data from the enclosing <pre> block, leaving only the csv
	-- data. If this results in an empty string, there was a problem.
    local rawCSV = trimmedText:match("<pre>(.-)</pre>")
	if rawCSV == "" then
		error("Final extraction of content resulted in no data left on data page: " .. dataPageName)
	end
    
    return rawCSV
end



---
--- Converts a CSV data string into a Lua table. The CSV data should have a
--- header row with field names. Each row represents a new record, and each
--- column contains specific data for that record. The resulting Lua table has
--- sub-tables for each row. Indices can be used or the names of the header row
--- will be usable as keys to access the fields.
---
--- For example:
---
--- row[1] is the same as row["id"] (if the first header in the header row
--- contains the string "id")
---
--- @param csvString (string) The CSV data as a string.
--- @return table, table of data from CSV, of header names for looking up indexes for the data table
function CsvUtils.luaTableFromCSV(csvString)
	
	-- Top level lua table, its header row, and its data rows (table of rows)
    local luaTable = {}
    local luaTableHeader = {}
    local luaTableDataRows = {}
	-- Lookup table for header names
	local headerLookup = {}
	
	-- Start by encoding any special characters in the string before processing.
	local encodedString = encodeCSV(csvString)
	if not encodedString or encodedString == "" then
		error("Encoding the csv data string removed all information.")
	end
	
    -- Separate the csv data into lines/rows by gmatch on carriage returns
	-- and/or newlines. Then make each line a new row (or the header row).
    for line in encodedString:gmatch("[^\r\n]+") do
		if not line or line == "" then
			error("Splitting csv data into rows failed.")
		end
		
		-- Only build the header once.
		if #luaTableHeader == 0 then
		
			-- Count the headers to use to populate the lookup table
			local i = 1
			
			-- Separate the header row into fields by gmatch this line again,
			-- this time on commas. We can use plus here because there
			-- are no empty header cells in well-structured CSV.
			for headerField in line:gmatch("([^,]+)") do
				if not headerField or headerField == "" then
					error("Splitting row into fields failed on header row.")
				end
				
				-- Then append each field to the header row and the inverse to
				-- the lookup table.
				luaTableHeader[i] = headerField
				headerLookup[headerField] = i
				i = i + 1
			end
			
			if #luaTableHeader == 0 then
				error("Adding fields was not successful to header row.")
			end
			
			-- Header row done; wait to incorporate it until the end.
		else
			-- Build each data row separately as a new table.
			local row = {}
			
			-- Increment a counter to align fields with their headers.
			local j = 1
			
			-- Separate the line into fields by gmatch on commas again. Use an
			-- asterisk here instead of a plus because there are empty cells
			-- with zero length. The rows must end in a comma to do this 
			-- correctly or there will be empty strings added between every
			-- field in the resulting table.
			for field in line:gmatch("([^,]*),") do
				-- Empty strings are allowed here.
				if not field then
					error("Splitting row into fields failed on field number: " .. i 
						.. " on non-header row number: " .. #luaTableDataRows+1)
				end
				
				-- Append each field to the row.
				row[j] = field
				j = j + 1
			end
			
			if #row == 0 then
				error("Adding fields was not successful to row number: " .. #luaTableDataRows+1)
			end
			
			-- Row done. Append to the bigger table.
			table.insert(luaTableDataRows, row)
		end
	end
	
	if #luaTableDataRows == 0 then
		error("There are no rows to add to the table.")
	end
	
	-- Assemble the table to return.
	table.insert(luaTable, luaTableHeader)
	table.insert(luaTable, luaTableDataRows)
	
    return luaTable, headerLookup
end

--endregion

return CsvUtils
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