Module:CsvUtils: Difference between revisions

From Against the Storm Official Wiki
m (missed a "M" that should be an "M.")
m (Correcting a few doc mistakes found after copying it into the module/doc page)
 
(6 intermediate revisions by the same user not shown)
Line 1: Line 1:
---
---
-- Module for processing retrieving and returning data stored in CSV format in
--- The CsvUtils module loads, processes, and returns data that is stored in CSV
-- wiki templates. There can be documentation in the template that will be
--- format in wiki templates.
-- automatically removed provided it is enclosed in <noinclude> block. The data
---
-- must be wrapped in <pre> to protect line breaks. The <pre> block will also
--- There can be documentation in the template, and this module will
-- be removed.
--- automatically remove it, provided it is enclosed in a <noinclude> block. The
-- @module CsvUtils
--- CSV data itself must be wrapped in a <pre> block in order to protect line
local M = {}
--- 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


---
---
-- Loads the data from a wiki page (usually a template). This method removes
--- Shortcut method for the two main methods of this module.
-- everything from the page content except the raw data, including anything
---
-- enclosed in <noinclude> and including the enclosing <pre> tags that protect
--- @param dataPageName string name of the template page containing the CSV data, including the namespace, like this: "Template:Workshops_Recipes_csv"
-- line breaks in the raw data. Returns nil if the page could not be loaded or
--- @return table of data from CSV
-- if there was a problem processing the page content.
--- @return table of header names for looking up indexes for the data table
--
function CsvUtils.extractTables(dataPageName)
-- @param dataPageName (string) The name of the page containing the CSV data,  
-- including the namespace, like this: 'Template:Workshops_Recipes_csv'
return CsvUtils.luaTableFromCSV(CsvUtils.extractCSV(dataPageName))
-- @return string The raw CSV data.
end
--
 
function M.extractCSV(dataPageName)
 
 
---
--- 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  
-- Load the page and verify something returned correctly. If the page was  
-- not found, then the variable will be nil or the page won't exist.
-- 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)
     local csvPage = mw.title.new(dataPageName)
     if not csvPage or not csvPage.exists then
     if not csvPage or not csvPage.exists then
         error("Could not find data page: " .. dataPageName)
         error("Site could not find data page: " .. dataPageName)
     end
     end
      
      
Line 32: Line 173:
     local pageContent = csvPage:getContent()
     local pageContent = csvPage:getContent()
if not pageContent or pageContent == "" then
if not pageContent or pageContent == "" then
error("Data page content does not exist: " .. dataPageName)
error("Content does not exist on data page: " .. dataPageName)
end
-- Process the content of the full wikipage, expanding templates and
-- applying wikimarkup. If it didn't work or returns an empty string, then
-- there's a problem.
local frame = mw.getCurrentFrame()
local preprocessedText = frame:preprocess(pageContent)
if not preprocessedText or preprocessedText == "" then
error("Data page content could not be preprocessed " .. dataPageName)
end
end
-- Remove everything within and including the <noinclude> tags. If this
-- Remove everything within and including the <noinclude> tags. If this
-- results in an empty string, there was a problem. Since we're still  
-- results in an empty string, there was a problem.
-- dealing with mediawiki content, use mw.ustring instead of Lua string
-- Since we're still dealing with mediawiki content, use MW library instead
-- library.
-- of Lua string library.
local trimmedText = mw.ustring.gsub(pageContent, "<noinclude>.-</noinclude>", "")
local trimmedText = mw.ustring.gsub(pageContent, "<noinclude>.-</noinclude>", "")
if trimmedText == "" then
if trimmedText == "" then
error("Trimming the data page content resulted in no csv data left: " .. dataPageName)
error("Trimming content resulted in no data left on data page: " .. dataPageName)
end
end
      
      
Line 57: Line 189:
     local rawCSV = trimmedText:match("<pre>(.-)</pre>")
     local rawCSV = trimmedText:match("<pre>(.-)</pre>")
if rawCSV == "" then
if rawCSV == "" then
error("Trimming the data page content resulted in no csv data left: " .. dataPageName)
error("Final extraction of content resulted in no data left on data page: " .. dataPageName)
end
end
      
      
     return rawCSV
     return rawCSV
end -- extractCSV function
end






---
---
-- Converts a CSV data string into a Lua table. The CSV data should have a
--- 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
--- 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  
--- 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  
--- 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.
--- 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  
--- For example:
-- contains the string "id")
---
--
--- row[1] is the same as row["id"] (if the first header in the header row
-- @function luaTableFromCSV
--- contains the string "id")
-- @param csvString (string) The CSV data as a string.
---
-- @return table A Lua table containing the CSV data.
--- @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 M.luaTableFromCSV(csvString)
function CsvUtils.luaTableFromCSV(csvString)
 
-- top level lua table, header row, and data rows (table of rows)
-- Top level lua table, its header row, and its data rows (table of rows)
     local luaTable = {}
     local luaTable = {}
     local header = {}
     local luaTableHeader = {}
     local rows = {}
     local luaTableDataRows = {}
local headerLookup = {} -- stores header indices for constant time lookup
-- Lookup table for header names
 
local headerLookup = {}
-- Start by cleaning (encoding) the string up so it can be processed without
-- getting confused by any special characters like commas or newlines within
-- Start by encoding any special characters in the string before processing.
-- quotations.
local encodedString = encodeCSV(csvString)
encodedString = M.encodeCSV(csvString)
if not encodedString or encodedString == "" then
if encodedString == "" then
error("Encoding the csv data string removed all information.")
error("Encoding the csv data string removed all information.")
end
end
 
     -- Separate the csv data into lines/rows by gmatch'ing on carriage returns  
     -- 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).
-- and/or newlines. Then make each line a new row (or the header row).
     for line in encodedString:gmatch("[^\r\n]+") do
     for line in encodedString:gmatch("[^\r\n]+") do
Line 102: Line 233:
end
end
-- We only build the header once; then its length will be > 0
-- Only build the header once.
-- The first line will be the header, and after we build that,
if #luaTableHeader == 0 then
-- everything else goes into the rows table.
if #header == 0 then
-- Count the headers to use to populate the lookup table
-- Count the headers to use to populate a header lookup table
local i = 1
local i = 1
-- Separate the header row into fields by gmatch'ing again, this
-- time on commas. We can use plus here because there are no empty
-- Separate the header row into fields by gmatch this line again,
-- header cells.
-- this time on commas. We can use plus here because there
for field in line:gmatch("([^,]+)") do
-- are no empty header cells in well-structured CSV.
if not field or field == "" then
for headerField in line:gmatch("([^,]+)") do
if not headerField or headerField == "" then
error("Splitting row into fields failed on header row.")
error("Splitting row into fields failed on header row.")
end
end
-- Then append each split field to the header row.
header[i] = field
-- Then append each field to the header row and the inverse to
headerLookup[field] = i
-- the lookup table.
luaTableHeader[i] = headerField
headerLookup[headerField] = i
i = i + 1
i = i + 1
end
end
-- Header row done; add it after all the other lines are processed.
if #luaTableHeader == 0 then
if #header == 0 then
error("Adding fields was not successful to header row.")
error("Adding fields was not successful to header row.")
end
end
-- Header row done; wait to incorporate it until the end.
else
else
-- Build each row separately as a new table.
-- Build each data row separately as a new table.
local row = {}
local row = {}
-- Keep track of indices so fields can be named with header row
-- names.
local i = 1
-- Separate the line into fields by gmatch'ing on commas again. Use
-- Increment a counter to align fields with their headers.
-- an asterisk here instead of a plus because there are empty cells  
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  
-- with zero length. The rows must end in a comma to do this  
-- correctly or there will be empty strings added between every
-- correctly or there will be empty strings added between every
Line 142: Line 275:
if not field then
if not field then
error("Splitting row into fields failed on field number: " .. i  
error("Splitting row into fields failed on field number: " .. i  
.. " on non-header row number: " .. #rows+1)
.. " on non-header row number: " .. #luaTableDataRows+1)
end
end
-- Append to the new row by assigning the key.
row[i] = field
-- Append each field to the row.
i = i + 1
row[j] = field
j = j + 1
end
end
-- Row done. Append the new row to the rows table now.
if #row == 0 then
if #row == 0 then
error("Adding fields was not successful to row number: " .. i)
error("Adding fields was not successful to row number: " .. #luaTableDataRows+1)
end
end
table.insert(rows, row)
-- Row done. Append to the bigger table.
table.insert(luaTableDataRows, row)
end
end
end
end
-- Now put the header and rows into the luaTable
if #luaTableDataRows == 0 then
if #rows == 0 then
error("There are no rows to add to the table.")
error("There are no rows to add to the table.")
end
end
table.insert(luaTable, header)
-- Assemble the table to return.
table.insert(luaTable, rows)
table.insert(luaTable, luaTableHeader)
table.insert(luaTable, luaTableDataRows)
     return luaTable, headerLookup
     return luaTable, headerLookup
end -- luaTableFromCSV function
---
-- Replaces apostrophes and double quotes in a string with their respective
-- HTML character codes.
--
-- @param stringToEncode The input string to be processed.
-- @return The modified string with special characters replaced.
--
function M.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 the content within quotes are handled:
-- Sub double quotes for their HTML code.
encodedString = encodedString:gsub("\"", "&quot;")
if encodedString == "" then
error("Encoding double quotation marks resulted in no data left.")
end
-- Sub single quotes for their HTML code.
encodedString = encodedString:gsub("'", "&#39;")
if encodedString == "" then
error("Encoding single quotation marks resulted in no data left.")
end
return encodedString
end
end


--endregion


 
return CsvUtils
---
-- Local function to replace newlines that occur within quoted strings with
-- their HTML codes, so that they aren't interpreted as newlines that separate
-- records in the csv data string.
--
-- @param stringToEncode The input string to be processed.
-- @return The modified string with newlines replaced.
function encodeQuotations(stringToEncode)
-- Sub out newlines within this matched quotation
local encodedString = stringToEncode:gsub('[\r\n]+', '&#10;')
if encodedString == "" then
error("Encoding newlines inside quoted descriptions resulted in no data left.")
end
-- Sub out commas within the matched quotation
local encodedString = encodedString:gsub(",", "&comma;")
if encodedString == "" then
error("Encoding commas inside quoted descriptions resulted in no data left.")
end
return encodedString
end

Latest revision as of 00:55, 16 November 2023

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