camelCaseToSnake

(t as table) =>
let
    // Function to check if a header is already in snake_case
    IsSnakeCase = (header as text) as logical =>
        Text.Contains(header, "_") and 
        Text.Lower(header) = header and 
        not List.AnyTrue(List.Transform({"A".."Z"}, each Text.Contains(header, _))),
    
    // Function to check if a header is a single word without mixed letters and numbers
    IsSingleWord = (header as text) as logical =>
        not Text.Contains(header, " ") and
        not List.AnyTrue(List.Transform({"A".."Z"}, each Text.Contains(header, _))) and
        not List.AnyTrue(List.Transform({"0".."9"}, each Text.Contains(header, _))),

    // Function to transform camelCase or mixed words to snake_case
    ToSnakeCase = (header as text) as text =>
        let
            // Find the positions of capital letters using Occurrence.All
            capitalPositions = Text.PositionOfAny(header, {"A".."Z"}, Occurrence.All),
            // Find the positions of numbers using Occurrence.All
            numberPositions = Text.PositionOfAny(header, {"0".."9"}, Occurrence.All),
            // Combine capital and number positions, including the start position
            positions = List.Sort(List.Distinct(List.Combine({{0}, capitalPositions, numberPositions}))),
            // Split the text at the positions
            splitWords = List.Transform(Splitter.SplitTextByPositions(positions)(header), each Text.Lower(_)),
            // Combine the words with underscores
            finalResult = Text.Combine(splitWords, "_"),
            finalResult2 = Text.Replace(finalResult," ","")
        in
            finalResult2,

    // Apply the transformation only to headers that need it
    Source = Table.TransformColumnNames(
        t, 
        each if IsSnakeCase(_) or IsSingleWord(_) then _ else ToSnakeCase(_)
    )
in
    Source