FSharp solution to the biggest puddle problem

BiggestPuddleOnePass.fsx

// F# solution to the biggest puddle problem posed at 
// http://geekswithblogs.net/BlackRabbitCoder/archive/2015/04/07/little-puzzlersndashlargest-puddle-on-a-bar-chart.aspx
// April 2015
// This solution works in one pass of the array

open System

let heights = [|10; 20; 80; 70; 60; 90; 40; 30; 40; 70|]
//let heights = [|10; 5; 10; 4; 5; 10|]
//let heights = [|0; 20; 80; 70; 60; 90; 40; 30; 40; 70|]
//let heights = [|20;1;11|]
//let heights = [||]

let puddleState depth currentPuddleSize maxPuddleSize =
    if depth > 0 then
        currentPuddleSize + depth, maxPuddleSize
    else
        0, max currentPuddleSize maxPuddleSize
    
let rec move idxCurrentLeft idxCurrentRight currentHeightLeft currentHeightRight currentPuddleSize maxPuddleSize movingRight =
    match idxCurrentLeft = idxCurrentRight with
    | false ->
        let depth, idxNewLeft, idxNewRight, newHeightLeft, newHeightRight =
            let edgeHeight = min currentHeightLeft currentHeightRight
                
            match movingRight with
            | true -> 
                let idxNextLeft = idxCurrentLeft + 1
                let newMaxLeft = max currentHeightLeft heights.[idxNextLeft]
                edgeHeight - heights.[idxNextLeft], idxNextLeft, idxCurrentRight, newMaxLeft, currentHeightRight
            | false -> 
                let idxNextRight = idxCurrentRight - 1
                let newMaxRight = max currentHeightRight heights.[idxNextRight]
                edgeHeight - heights.[idxNextRight], idxCurrentLeft, idxNextRight, currentHeightLeft, newMaxRight
        let nextMoveIsToRight = heights.[idxNewLeft] <= heights.[idxNewRight]    
        let newPuddleState = puddleState depth currentPuddleSize maxPuddleSize
        move idxNewLeft idxNewRight newHeightLeft newHeightRight (fst newPuddleState) (snd newPuddleState) nextMoveIsToRight
    | true -> maxPuddleSize 

let calcPuddleSize h = 
    match h with
    | [||] -> 0
    | _ -> move 0 (h.Length-1) h.[0] h.[h.Length-1] 0 0 true

let maxPuddleSize = calcPuddleSize heights