Module:Table

Module for searching and manipulating wikitables.

---

-- Module for searching and manipulating wikitables.

local p = {}

local function delimiterPositions(wikitable, delimiter, ender)
    -- Gets the positions and number of instances of a delimiter in a table's wikitext. By "position", we mean that, for example, the letter "e" in "hello" is in position 2, and the pattern "ll" in "hello" is in position 3.
    local positions = {}
    local index = 1

    for pos = 1, string.len(wikitable) - 1 do
        if string.sub(wikitable, pos, pos + string.len(delimiter) - 1) == delimiter then
            positions[index] = pos
            index = index + 1
        elseif string.sub(wikitable, pos, pos + string.len(ender) - 1) == ender then
            positions[index] = pos
            break
        end
    end

    return {positions, index - 1}
end

local function rowPositions(wikitable)
    -- Gets the positions of instances of the row delimiter |- in a table's wikitext.
    return delimiterPositions(wikitable, "|-", "|}")[1]
end

local function rows(wikitable)
    -- Gets the number of rows in a table's wikitext.
    return delimiterPositions(wikitable, "|-", "|}")[2]
end

local function fetchRows(wikitable, firstRow, lastRow)
    -- Gets the contents of the rows between firstRow and lastRow inclusively. For example, fetchRows(wikitable, 3, 7) returns rows 3, 4, 5, 6, and 7 of the table.
    local rowP = rowPositions(wikitable)
    return string.sub(wikitable, rowP[firstRow], rowP[lastRow + 1])
end

local function fetchOneRow(wikitable, row)
    -- Gets the contents of a single row.
    return fetchRows(wikitable, row, row)
end

local function columnPositions(rowText)
    -- Gets the positions of instances of the column delimiter | in a table row's wikitext.
    return delimiterPositions(rowtext, "|", "$")[1]
end

local function columns(rowtext)
    -- Gets the number of columns in a table's wikitext.
    return delimiterPositions(rowtext, "|", "$")[2]
end

local function findFirstRow(wikitable, str, col)
    newCol = col or 0
    rowP = rowPositions(wikitable)
    for pos = 1, string.len(wikitable) - 1 do
        if string.sub(wikitable, pos, pos + string.len(str) - 1) == str then
            for n = 1, rows(wikitable) do
                if rowP[n] > pos then
                    if newCol == 0 then
                        return rowP[n - 1]
                    else
                        rowContent = fetchOneRow(wikitable, n - 1)
                        colP = columnPositions(rowContent)
                        for m = 1, columns(rowContent) do
                            if colP[m] > pos and colP[m - 1] == newCol then
                                return colP[m - 1]
                            end
                        end
                    end
                end
            end
        end
    end
    return 0
end

local function columns(wikitable)
    -- Gets the names of the columns.
    names = {}
    posTable = delimiterPositions(wikitable, "!", "|-")
    for n = 1, posTable[2] do
        names[n] = string.sub(wikitable, posTable[1][n] + 1, posTable[1][n + 1] - 1)
    end
    return names
end

function p.partialTable(frame)
    -- Constructs a subtable of the given table containing the specified range of rows. For example, {{#invoke:table|partialTable|(table)|3|7}} produces a table using rows 3-7 of the original table.
    local wikitable = frame.args[1]
    local rowP = rowPositions(wikitable)
    local length = rows(wikitable)
    local firstRow = math.max(frame.args[2], 1) or 1
    local lastRow = math.min(frame.args[3], length) or length
    local header = string.sub(wikitable, 1, rowP[1] - 1)
    local body = fetchRows(wikitable, firstRow, lastRow)
    return header .. body .. "}"
end

function p.conditionalPartialTable(frame)
    -- Like p.partialTable but with row ranges specified using table contents. Usage: {{#invoke:table|conditionalPartialTable|(table)|first=|last=|col=(column number (optional))}}
    -- For example, {{#invoke:table|conditionalPartialTable|(table)|1970|1980|col=1}} finds the first row where column 1 contains 1970 and the first row where column 1 contains 1980, and produces a table using all the rows in between except the row containing 1980.
    local wikitable = frame.args[1]
    local rowP = rowPositions(wikitable)
    local length = rows(wikitable)
    local firstRow = findFirstRow(wikitable, frame.args["first"], frame.args["col"]) or findFirstRow(wikitable, frame.args["first"]) or 1
    local lastRow = findFirstRow(wikitable, frame.args["last"], frame.args["col"]) or findFirstRow(wikitable, frame.args["last"]) or length
    lastRow = lastRow - 1
    local header = string.sub(wikitable, 1, rowP[1] - 1)
    local body = fetchRows(wikitable, firstRow, lastRow)
    return header .. body .. "}"
end

return p

--[[Category:Modules]]