local p = {}

---------------------------------------------
-- Helper function to parse a row from a
-- wikitext table.
---------------------------------------------
local function parseRow(cells, headerMap)
    -- We need rank, page title, and views
    if not (headerMap.rank and headerMap.page and headerMap.views) then 
        return nil 
    end

    local entry = {}
    
    -- rank
    entry.rank = tonumber(cells[headerMap.rank])
    
    -- page title
    local pageCell = cells[headerMap.page] or ""
    entry.page = pageCell:match("%[%[:?([^|%]]+)")

    -- views
    local viewsCell = cells[headerMap.views] or ""
    local viewsNum = viewsCell:match("{{FORMATNUM:(%d+)}}") or viewsCell:match("(%d+)")
    entry.views = tonumber(viewsNum)

    -- toolforge URL
    if entry.page then
        entry.url = "https://pageviews.toolforge.org/?project=en.wikipedia.org&pages=" .. entry.page:gsub(" ", "_")
    end

    -- assessment (optional)
    if headerMap.assessment and cells[headerMap.assessment] then
        local cell = cells[headerMap.assessment]
        entry.assessment = cell:match("Category:([^%-]+)%-Class") or cell:match("{{([^}%-]+)%-Class}}")
    end

    -- importance (optional)
    if headerMap.importance and cells[headerMap.importance] then
        local cell = cells[headerMap.importance]
        entry.importance = cell:match("Category:([^%-]+)%-importance") or cell:match("{{([^}%-]+)%-importance}}")
    end

    -- ensure we have the required data 
	-- (we can render without assessment or importance)
    return (entry.rank and entry.page and entry.views) and entry or nil
end

---------------------------------------------
-- Main function top7 will create a list of 7
-- or specified number of list items.
---------------------------------------------
function p.top7(frame)
    local pageName = frame.args[1] or ""
    local limit = tonumber(frame.args[2]) or 7

    if pageName == "" then
        return "ERROR: Missing page name parameter ([[Template:Popular list/doc#Missing page name parameter|help]])"
    end

    local title = mw.title.new(pageName)
	if not title then
		return "ERROR: Invalid page name '" .. pageName .. "' ([[Template:Popular list/doc#Invalid page name|help]])"
	end
	
    local pageContent = title and title:getContent()
    if not pageContent then
        return "ERROR: Page does not exist or cannot be read ([[Template:Popular list/doc#Page does not exist|help]])"
    end

    -- NORMALIZATION: Handle double-pipes and double-exclamations
    pageContent = pageContent:gsub("%s*||%s*", "\n|"):gsub("%s*!!%s*", "\n!")

    local entries = {}
    local headerMap = {}
    local currentRow = {}
    local inTable = false

    -- Line-by-line processing
    for line in (pageContent .. "\n"):gmatch("(.-)\n") do
        line = mw.text.trim(line)

        if line:match("^{|") then
            inTable = true
        elseif line:match("^|}") then
            -- Process the final row before closing
            if #currentRow > 0 and inTable then
                local entry = parseRow(currentRow, headerMap)
                if entry and entry.rank <= limit then table.insert(entries, entry) end
            end
            break
        elseif inTable and line:match("^[|!]%-") then
            -- A row is finished. Determine if it was a Header row or Data row.
            if #currentRow > 0 then
                local isHeaderRow = false
                for _, val in ipairs(currentRow) do
                    if val:find("Rank") or val:find("Page") then isHeaderRow = true break end
                end

                if isHeaderRow then
                    for i, content in ipairs(currentRow) do
                        local lowContent = content:lower()
                        if lowContent:find("rank") then headerMap.rank = i
                        elseif lowContent:find("page") or lowContent:find("article") then headerMap.page = i
                        elseif lowContent:find("class") or lowContent:find("assessment") then headerMap.assessment = i
                        elseif lowContent:find("importance") then headerMap.importance = i
                        -- Precision Views check (excludes "daily", "day", etc.)
                        elseif lowContent:find("views") and not lowContent:find("da") then
                            if content == "Views" or not headerMap.views then
                                headerMap.views = i
                            end
                        end
                    end
                else
                    -- It's a data row, parse it using the map we built
                    local entry = parseRow(currentRow, headerMap)
                    if entry and entry.rank <= limit then 
                        table.insert(entries, entry) 
                    end
                end
            end
            currentRow = {}
        elseif inTable and (line:match("^|") or line:match("^!")) then
            -- Capture cell content, removing the leading | or !
            local cellData = line:match("^[|!]+%s*(.*)$")
            if cellData then table.insert(currentRow, cellData) end
        end
    end

    -- Validate that we actually found the table structure
    if not (headerMap.rank and headerMap.page and headerMap.views) then
        return "ERROR: No wikitable found on page ([[Template:Popular list/doc#No wikitable found on page|help]])"
    end

    if #entries == 0 then
        return "ERROR: No entries found in table ([[Template:Popular list/doc#No entries found in table|help]])"
    end

    -- Sort by rank (1, 2, 3...)
    table.sort(entries, function(a, b) return a.rank < b.rank end)

    -- BUILD OUTPUT (Your "Pile-on" Logic)
    local list = mw.html.create('ol'):addClass('popular-list')
    
    for _, entry in ipairs(entries) do
        local formattedViews = mw.language.getContentLanguage():formatNum(entry.views)
        local annotatedLink = frame:preprocess("{{Annotated link|" .. entry.page .. "}}")
        
        -- Start string: (VIEWS
        local metaStr = "(" .. string.format("[%s %s views]", entry.url, formattedViews)
        
        -- Add Assessment if it exists
        if entry.assessment and entry.assessment ~= "" then
            metaStr = metaStr .. ", " .. entry.assessment .. " rating"
        end
        
        -- Add Importance if it exists
        if entry.importance and entry.importance ~= "" then
            metaStr = metaStr .. ", " .. entry.importance .. " importance"
        end
        
        -- Cap it: )
        metaStr = metaStr .. ")"

        -- Format as: Link ''(Metadata)''
        local itemText = string.format("%s ''%s''", annotatedLink, metaStr)
        list:tag('li'):wikitext(itemText)
    end

    return tostring(list)
end

return p