--[=[ 2013-05-07
LuaWiki - Support Lua programming in Wiki environment
* .getArg()
* .initVariables()
* .getVariable()
* .isExisting()
* .setFrame()
* .transclude()
]=]



-- Module globals
local wikiVariables
local LuaWiki = {}



LuaWiki.error = function ( about )
    -- Enclose errorMsg with <span>
    -- Precondition:
    --     about  -- string
    local r = about
    if type( about ) == "string" then
        if #about == 0 then
            r = "Error in Lua"
        end
    else
        r = tostring( about )
    end
    return "<span class='error'>" .. error( r, 3 ) .. "</span>"
end -- LuaWiki.error()



LuaWiki.getArg = function ( arg, assign )
    -- Retrieve template argument
    -- Precondition:
    --     arg     -- string or number; argument identifier
    --     assign  -- any, optional; default value
    -- Uses:
    --     mw.getCurrentFrame()
    local r = mw.getCurrentFrame().args[ arg ]
    if type( r ) ~= "string" then
        if type( assign ) == nil then
            r = "{{{<" .. arg .. ">}}}"
        else
            r = assign
        end
    end
    return r
end -- LuaWiki.getArg()



LuaWiki.getVariable = function ( seek, numeric )
    -- Retrieve item from wikiVariables; populate if not yet present
    -- Precondition:
    --     seek     -- string; name of variable
    --     numeric  -- true: seek is numeric (else string)
    -- Uses:
    --     >< wikiVariables
    --     mw.getCurrentFrame()
    local g, i, n
    local r = false
    if type( wikiVariables ) == "table" then
        n = #wikiVariables
        for i = 1, n do
            g = wikiVariables[ i ]
            if g then
                if g[ 1 ] == seek then
                    r = g[ 2 ]
                    break;
                end
            end
        end -- for i
    else
        wikiVariables = { }
        n = 0
    end
    if not r then
        g = mw.getCurrentFrame():preprocess( "{{" .. seek .. "}}" )
        r = mw.ustring.match( g, "^(.*)$" )
        if numeric then
            r = tonumber( g )
        end
        table.insert( wikiVariables,  n + 1,  { seek, r } )
    end
    return r
end -- LuaWiki.getVariable()



LuaWiki.initVariables = function ( request )
    -- Initialize wikiVariables
    -- Precondition:
    --     request  -- table; every element either
    --                        * string; name of variable
    --                        * table; name string and true, if numeric
    -- Uses:
    --      < wikiVariables
    --     mw.getCurrentFrame()
    local g, i, n, s
    local src = "|"
    wikiVariables = { }
    for i = 1, #request do
         s = request[ i ]
         if type( s ) == "table" then
             s = s[ 1 ]
         end
         src = src .. s .. "={{" .. s .. "}}|"
    end -- for i
    src = mw.getCurrentFrame():preprocess( src )
    for i = 1, #request do
        s = request[ i ]
        n = ( type( s ) == "table" )
        if n then
            n = s[ 2 ]
        end
        if n then
            g = "-?%d+"
            s = s[ 1 ]
        else
            g = "[^|]*"
        end
        g = mw.ustring.match( src,  "|" .. s .. "=(" .. g .. ")|" )
        if n then
            g = tonumber( g )
        end
        table.insert( wikiVariables,  i,  { s, g } )
    end -- for i
end -- LuaWiki.initVariables()



LuaWiki.isExisting = function ( seek )
    -- Return true if page exists, else false
    -- Precondition:
    --     seek  -- string; full page name
    -- Uses:
    --     mw.getCurrentFrame()
    local g = mw.getCurrentFrame():callParserFunction( "#ifexist",
                                                       { seek,
                                                         "1",
                                                         "0" } )
    return ( g == "1" )
end -- LuaWiki.isExisting()



LuaWiki.transclude = function ( s, args )
    -- Save transclusion of a page, or error message
    -- Precondition:
    --     s     -- string; page name
    --     args  -- table or nil; arguments
    -- Uses:
    --     mw.getCurrentFrame()
    --     error()
    local r = { s, "1" }
    local frame = mw.getCurrentFrame()
    if frame:callParserFunction( "#ifexist", r ) == "1" then
        if args then
            r = frame:expandTemplate{ title = s, args = args }
        else
            r = frame:expandTemplate{ title = s }
        end
    else
        r = error( "No transclude page '" .. s .. "'" )
    end
    return r
end -- LuaWiki.transclude()



return LuaWiki