Editing Module:Category handler

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--                                                                                                      --
--                                          CATEGORY HANDLER                                            --
--                                                                                                      --
--      This module implements the {{category handler}} template in Lua, with a few improvements: all   --
--      namespaces and all namespace aliases are supported, and namespace names are detected            --
--      automatically for the local wiki. This module requires [[Module:Namespace detect]] and          --
--      [[Module:Yesno]] to be available on the local wiki. It can be configured for different wikis    --
--      by altering the values in the "cfg" table.                                                      --
--                                                                                                      --
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--                                          Configuration data                                          --
--                      Language-specific parameter names and values can be set here.                   --
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local cfg = {}

-- The following config values set the names of parameters that suppress categorisation. They are used
-- with Module:Yesno, and work as follows:
--
-- cfg.nocat:
-- Result of yesno(args[cfg.nocat])         Effect
-- true                                     Categorisation is suppressed
-- false                                    Categorisation is allowed, and the blacklist check is skipped
-- nil                                      Categorisation is allowed
--
-- cfg.categories:
-- Result of yesno(args[cfg.categories])    Effect
-- true                                     Categorisation is allowed, and the blacklist check is skipped
-- false                                    Categorisation is suppressed
-- nil                                      Categorisation is allowed
cfg.nocat = 'nocat'    
cfg.categories = 'categories'

-- The parameter name for the legacy "category2" parameter. This skips the blacklist if set to the
-- cfg.category2Yes value, and suppresses categorisation if present but equal to anything other than
-- cfg.category2Yes or cfg.category2Negative.
cfg.category2 = 'category2'
cfg.category2Yes = 'yes'
cfg.category2Negative = '¬'

-- cfg.subpage is the parameter name to specify how to behave on subpages. cfg.subpageNo is the value to
-- specify to not categorise on subpages; cfg.only is the value to specify to only categorise on subpages.
cfg.subpage = 'subpage'
cfg.subpageNo = 'no'
cfg.subpageOnly = 'only'

-- The parameter for data to return in all namespaces.
cfg.all = 'all'

-- The parameter name for data to return if no data is specified for the namespace that is detected. This
-- must be the same as the cfg.other parameter in [[Module:Namespace detect]].
cfg.other = 'other'

-- The parameter name used to specify a page other than the current page; used for testing and
-- demonstration. This must be the same as the cfg.page parameter in [[Module:Namespace detect]].
cfg.page = 'page'

-- The categorisation blacklist. Pages that match Lua patterns in this list will not be categorised.
-- (However, see the explanation of cfg.nocat, cfg.categories and cfg.category2 for some exceptions.)
-- If the namespace name has a space in, it must be written with an underscore, e.g. "Wikipedia_talk".
-- Other parts of the title can have either underscores or spaces.
cfg.blacklist = {
    '^Main Page$', -- don't categorise the main page.
    
    -- Don't categorise the following pages or their subpages.
    '^Wikipedia:Cascade%-protected items$',
    '^Wikipedia:Cascade%-protected items/.*$',
    '^User:UBX$', -- The userbox "template" space.
    '^User:UBX/.*$',
    '^User_talk:UBX$',
    '^User_talk:UBX/.*$',
    
    -- Don't categorise subpages of these pages, but allow
    -- categorisation of the base page.
    '^Wikipedia:Template messages/.+$',
    
    '/[aA]rchive' -- Don't categorise archives.
}

-- This is a table of namespaces to categorise by default. They should be in the format of parameter
-- names accepted by [[Module:Namespace detect]].
cfg.defaultNamespaces = {
    'main',
    'file',
    'help',
    'category'
}

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--                                          End configuration data                                      --
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-- Get dependent modules
local nsDetect = require('Module:Namespace detect/sandbox') -- REMOVE "/sandbox" BEFORE GOING LIVE
local yesno = require('Module:Yesno')

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--                                          Local functions                                             --
--      The following are internal functions, which we do not want to be accessible from other modules. --
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-- Find whether we need to return a category or not.
local function needsCategory(pageObject, args)
    -- Don't categorise if the relevant options are set.
    if yesno(args[cfg.nocat])
        or yesno(args[cfg.categories]) == false
        or (
            args[cfg.category2] 
            and args[cfg.category2] ~= cfg.category2Yes 
            and args[cfg.category2] ~= cfg.category2Negative
        )
    then
        return false
    end
    -- If there is no pageObject available, then that either means that we are over
    -- the expensive function limit or that the title specified was invalid. Invalid
    -- titles will probably only be a problem during testing, so we choose the best
    -- fallback for being over the expensive function limit. The fallback behaviour
    -- of the old template was to assume the page was not a subpage, so we will do
    -- the same here.
    if args[cfg.subpage] == cfg.subpageNo and pageObject and pageObject.isSubpage then
        return false
    end
    if args[cfg.subpage] == cfg.subpageOnly 
        and (not pageObject or (pageObject and not pageObject.isSubpage))
    then
        return false
    end
    return true
end

-- Find whether we need to check the blacklist or not.
local function needsBlacklistCheck(args)
    if yesno(args[cfg.nocat]) == false
        or yesno(args[cfg.categories]) == true
        or args[cfg.category2] == cfg.category2Yes
    then
        return false
    else
        return true
    end
end

-- Find whether any namespace parameters have been specified.
-- Mappings is the table of parameter mappings taken from
-- [[Module:Namespace detect]].
local function nsParamsExist(mappings, args)
    if args[cfg.all] or args[cfg.other] then
        return true
    end
    for ns, params in pairs(mappings) do
        for i, param in ipairs(params) do
            if args[param] then
                return true
            end
        end
    end
    return false
end

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--                                          Global functions                                            --
--      The following functions are global, because we want them to be accessible from #invoke and      --
--      from other Lua modules.                                                                         --
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local p = {}

-- Find if a string matches the blacklist. Returns the match if one is found, or nil otherwise.
-- Input should be a page title with a namespace prefix, e.g. "Wikipedia talk:Articles for deletion".
function p.matchesBlacklist(page)
    if type(page) ~= 'string' then return end
    for i, pattern in ipairs(cfg.blacklist) do
        local match = mw.ustring.match(page, pattern)
        if match then
            return match
        end
    end
end

-- The main structure of the module. Checks whether we need to categorise,
-- and then passes the relevant arguments to [[Module:Namespace detect]].
function p._main(args)
    -- Get the page object and argument mappings from
    -- [[Module:Namespace detect]], to save us from having to rewrite the
    -- code.
    local pageObject = nsDetect.getPageObject(args[cfg.page])
    local mappings = nsDetect.getParamMappings()
    
    if not needsCategory(pageObject, args) then return end
    
    local ret = ''
    -- Check blacklist if necessary.
    if not needsBlacklistCheck(args) or not p.matchesBlacklist(pageObject.prefixedText) then
        if not nsParamsExist(mappings, args) then
            -- No namespace parameters exist; basic usage. Pass args[1] to
            -- [[Module:Namespace detect]] using the default namespace
            -- parameters, and return the result.
            local ndargs = {}
            for _, ndarg in ipairs(cfg.defaultNamespaces) do
                ndargs[ndarg] = args[1]
            end
            ndargs.page = args.page
            ndargs.demospace = args.demospace
            local ndresult = nsDetect._main(ndargs)
            if ndresult then
                ret = ret .. ndresult
            end
        else
            -- Namespace parameters exist; advanced usage.
            -- If the all parameter is specified, return it.
            local all = args.all
            if type(all) == 'string' then
                ret = ret .. all
            end
            
            -- Get the arguments to pass to [[Module:Namespace detect]].
            local ndargs = {}
            for ns, params in pairs(mappings) do
                for _, param in ipairs(params) do
                    ndargs[param] = args[param] or args[cfg.other] or nil
                end
            end
            ndargs.other = args.other
            ndargs.page = args.page
            ndargs.demospace = args.demospace
            
            local data = nsDetect._main(ndargs)
            
            -- Work out what to return based on the result of the namespace detect call.
            local datanum = tonumber(data)
            if type(datanum) == 'number' then
                -- "data" is a number, so return that positional parameter.
                -- Remove non-positive integer values, as only positive integers
                -- from 1-10 were used with the old template.
                if datanum > 0 and math.floor(datanum) == datanum then
                    local dataArg = args[datanum]
                    if type(dataArg) == 'string' then
                        ret = ret .. dataArg
                    end
                end
            else
                -- "data" is not a number, so return it as it is.
                if type(data) == 'string' then
                    ret = ret .. data
                end
            end
        end
    end
    return ret
end

function p.main(frame)
    -- If called via #invoke, use the args passed into the invoking
    -- template, or the args passed to #invoke if any exist. Otherwise
    -- assume args are being passed directly in.
    local origArgs
    if frame == mw.getCurrentFrame() then
        origArgs = frame:getParent().args
        for k, v in pairs(frame.args) do
            origArgs = frame.args
            break
        end
    else
        origArgs = frame
    end

    -- Trim whitespace and remove blank arguments for the following args:
    -- 1, 2, 3 etc., "nocat", "categories", "subpage", and "page".
    local args = {}
    for k, v in pairs(origArgs) do
        if type(v) == 'string' then
            v = mw.text.trim(v) -- Trim whitespace.
        end
        if type(k) == 'number'
            or k == cfg.nocat
            or k == cfg.categories
            or k == cfg.subpage
            or k == cfg.page
        then
            if v ~= '' then
                args[k] = v
            end
        else
            args[k] = v
        end
    end
    
    -- Lower-case "nocat", "categories", "category2", and "subpage". These
    -- parameters are put in lower case whenever they appear in the old
    -- template, so we can just do it once here and save ourselves some work.
    local lowercase = {cfg.nocat, cfg.categories, cfg.category2, cfg.subpage}
    for _, v in ipairs(lowercase) do
        local argVal = args[v]
        if type(argVal) == 'string' then
            args[v] = mw.ustring.lower(argVal)
        end
    end
    
    return p._main(args)
end

return p