# How to create form letters from spreadsheet data in ConTeXt?

In LaTeX, one can use datatool to build simple form letters. As an example, the data is stored in a spreadsheet or CSV file, like this:

Name,Amount,Date
"Mr. White","$300","Dec. 2, 1911" "Mr. Brown","$300","Dec. 3, 1911"


Then, one provides a simple template:

Dear \insertName,

You owe \insertAmount. Please send it before \insertDate.


When compiled, it produces one letter for each row in the spreadsheet.

Are there similar tools for creating form letters in ConTeXt? The M-database module appears to share much of the functionality of datatool, but I cannot see any way to use this to create form letters.

-

Afaict there is nothing builtin. But as often you can get there by combining some of the existing functionality. All you need is a CSV parser and you can use buffers to do the rest. (I modified the interface a bit so you can simply \insert[Field Name] instead of \insertFieldName.) The usage is as follows:

1. Define a template. In the revised form, your example code would look like this:

\startcsvtemplate [tpl]
Dear \insert[Name],

You owe \insert[Amount]. Please send it before \insert[Date].
\par
\stopcsvtemplate


Trailing endlines are stripped, so you will have to request paragraphs explicitly.

2. Define an input buffer (optional): Input can be read from a file or from a buffer. In the latter case, the buffer needs to be defined, just like any other buffer:

\startbuffer[csdata]
Name,Amount,Date
"Mr. White","\\letterdollar 300","Dec. 2, 1911"
"Mr. Brown","\\letterdollar 300","Dec. 3, 1911"
"Ms. Premise","\\letterdollar 42","Dec. 4, 1911"
"Ms. Conclusion","\\letterdollar 23","Dec. 5, 1911"
\stopbuffer

3. Request the input to be parsed: Depending on whether you chose to read the data from a buffer or from a file, you will have to process it using the appropriate command:

\processcsvbuffer[one][csdata]
\processcsvfile[two][test.csv]


The first argument of either command is the id by which the dataset can be referenced later (similar to \useexternalfigure[a_cow][cow.pdf]).

4. Now that dataset and template are in place, you can use them together in a job definition:

\definecsvjob [testing] [
data=two,
template=tpl,
]


This will generate a macro \testing which you can use in your document to generate the output.

\starttext \testing \stoptext


NB: The answer below can (and probably should, if used frequently) be improved by defining some template language and moving the string processing to Lua entirely. As it is, the performance will be poor due to the repeated calls to Lua from TeX.

% macros=mkvi

\unprotect
\startluacode
local datasets = { }

local buffersraw   = buffers.raw
local context      = context
local lpegmatch    = lpeg.match
local stringformat = string.format
local stringmatch  = string.match
local stringsub    = string.sub
local tableconcat  = table.concat
local tableswapped = table.swapped

local die = function (msg) print(msg or "ERROR") os.exit(1) end

local csv_parser
do
--- This is (more than) an RFC 4180 parser.
--- http://tools.ietf.org/html/rfc4180
local C, Cg, Cs, Ct, P, S, V
= lpeg.C, lpeg.Cg, lpeg.Cs, lpeg.Ct, lpeg.P, lpeg.S, lpeg.V

local backslash = P[[\letterbackslash]]
local comma     = ","
local dquote    = P[["]]
local eol       = S"\n\r"^1
local noquote   = 1 - dquote
local unescape  = function (s) return stringsub(s, 2) end
csv_parser = P{
"file",
file    = Ct((V"header" * eol)^-1 * V"records"),
records = V"record" * (eol * V"record")^0 * eol^0,
record  = Ct(V"field" * (comma * V"field")^0),
name    = V"field",
field   = V"escaped" + V"non_escaped",
--- Deviate from rfc: the “textdata” terminal was defined only
--- for 7bit ASCII. Also, any character may occur in a quoted
--- field as long as it is escaped with a backslash. (\TEX\
escaped     = dquote
* Cs(((backslash * 1 / unescape) + noquote)^0)
* dquote
,
non_escaped = C((1 - dquote - eol - comma)^0),
}
end

local process = function (id, raw)
--- buffers may have trailing EOLs
raw = stringmatch(raw, "^[\n\r]*(.-)[\n\r]*$") local data = lpegmatch(csv_parser, raw) --- map column name -> column nr data.header = tableswapped(data.header) datasets[id] = data end --- escaping hell ahead, please ignore. local s_item = [[ \bgroup \string\def\string\insert{\string\getvalue{csv_insert_field}{%s}{%s}}%% %s%% template \egroup ]] local typeset = function (id, template) local data = datasets[id] or die("ERROR unknown dataset: " .. id) template = stringmatch(buffersraw(template), "^[\n\r]*(.-)[\n\r]*$")
local result = { }
local last = \letterhash data
for i=1, last do
result[i] = stringformat(s_item, id, i, template)
end
context(tableconcat(result))
end

local insert = function (id, n, field)
local this = datasets[id]
end

commands.process_csv      = process
commands.process_csv_file = function (id, fname)
end
commands.typeset_csv_job  = typeset
commands.insert_csv_field = insert

\stopluacode

\startinterface all
\setinterfaceconstant{template}{template}
\setinterfaceconstant    {data}{data}
\stopinterface

\def\processcsvbuffer[#id][#buf]{%
\ctxcommand{process_csv([[#id]], buffers.raw(\!!bs#buf\!!es))}%
}

\def\processcsvfile[#id][#filename]{%
\ctxcommand{process_csv_file([[#id]], \!!bs\detokenize{#filename}\!!es)}%
}

%% modeled after \startbuffer
\setuvalue{\e!start csvtemplate}{%
\begingroup
\obeylines
\dosingleempty\csv_template_start%
}

\def\csv_template_start[#id]{%
\buff_start_indeed{}{#id}{\e!start csvtemplate}{\e!stop csvtemplate}%
}

\installnamespace                  {csvjob}
\installcommandhandler \????csvjob {csvjob} \????csvjob

\appendtoks
\setuevalue{\currentcsvjob}{\csv_job_direct[\currentcsvjob]}
\to \everydefinecsvjob

\unexpanded\def\csv_job_direct[#id]{%
\edef\currentcsvjob{#id}%
\dosingleempty\csv_job_indeed%
}

\def\csv_job_indeed[#setups]{%
\iffirstargument\setupcurrentcsvjob[#setups]\fi
\ctxcommand{typeset_csv_job(
[[\csvjobparameter\c!data]],
[[\csvjobparameter\c!template]])}%
}

\def\csv_insert_field#id#n[#field]{%
\ctxcommand{insert_csv_field([[#id]], #n, [[#field]])}%
}

\protect

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%                               demo
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% Stepwise instructions.
%% step 1: Define template.
\startcsvtemplate [tpl]
Dear \insert[Name],

You owe \insert[Amount]. Please send it before \insert[Date].
\par
\stopcsvtemplate

%% step 2: Define an input (CSV).
\startbuffer[csdata]
Name,Amount,Date
"Mr. White","\\letterdollar 300","Dec. 2, 1911"
"Mr. Brown","\\letterdollar 300","Dec. 3, 1911"
"Ms. Premise","\\letterdollar 42","Dec. 4, 1911"
"Ms. Conclusion","\\letterdollar 23","Dec. 5, 1911"
\stopbuffer

%% step 3: Parse and store the input.
\processcsvbuffer[one][csdata]
%\processcsvfile[two][test.csv]

%% step 4: Declare a job, joining dataset and template.
\definecsvjob [testing] [
data=two,
template=tpl,
]

%% step 5: Enjoy!
\starttext
\testing
\stoptext

-

I don't know how to use ConTeXt, but I know that you can use LuaTex in ConTeXt, so I give you a LuaLaTeX example which is easy to port to ConTeXt because the main work is done in Lua. The principle is that you define a template of the letter in the LaTeX/ConTeXt-world including some LaTeX/ConTeXt macros (variables) and call the template repetitively from LuaTeX with each time redefined variables for each entry in the given csv file. Before you can do this you have to read the csv file and store the data in a Lua table.

Maybe it would be a cleaner solution to use arguments (#1,#2,#3,...) in the letter template instead of redefining the variables each time but then the template is not easy to read by the user because he don't know the meaning of the arguments and you are also limited to nine arguments. It's your choice.

\documentclass{article}
\usepackage{filecontents}

\begin{filecontents*}{datafile.csv}
Mr.;Homer;Simpson;Evergreen Terrace, Springfield
Ms.;Marge;Simpson;Evergreen Terrace, Springfield
Mr.;Bart;Simpson;Evergreen Terrace, Springfield
Ms.;Lisa;Simpson;Evergreen Terrace, Springfield
Ms.;Maggie;Simpson;Evergreen Terrace, Springfield
\end{filecontents*}

\begin{filecontents*}{luaFunctions.lua}

function ReadData()

local input = io.open('datafile.csv', 'r')
dataTable = {}

for line in input:lines() do

-- split the line
local split = string.explode(line, ";")

-- store the arguments in variables
tableItem = {}
tableItem.Sex = split[1]
tableItem.FirstName = split[2]
tableItem.SurName = split[3]

-- insert the arguments of one line in the table
table.insert(dataTable, tableItem)
end
end

-- redefine the latex commands and execute the \letterTemplate macro
tex.print(string.format("\\def\\sex{%s}",sex))
tex.print(string.format("\\def\\firstName{%s}",firstName))
tex.print(string.format("\\def\\surName{%s}",surName))
tex.print("\\letterTemplate")
end

function PrintLetter()
-- read the external file and store the data in a table

-- loop through the table and print a letter for each table item
for i,p in ipairs(dataTable) do

-- pagebreak
if i ~= #dataTable then
tex.print("\\newpage")
end
end
end

\end{filecontents*}

\directlua{dofile("luaFunctions.lua")}

\def\letterTemplate{%
Hallo \sex\ \firstName,\\