param(
	[Parameter(Mandatory=$true)]$File
)

$lines = foreach($ln in Get-Content $File) {
	if($ln -match '^(\t*)(.+)$') {
		@{
			originalText = $ln
			text = $Matches[2]
			indentLevel = $Matches[1].Length
		}
	}
}
$lines = $lines | ? { $_.text -and $_.text.Trim() }

function create-Indents($count) {
	return ([System.Linq.Enumerable]::Range(0, $count) | % { "	" }) -join ''
}
function parse-Tree($currentLine, $lines) {
	function writein($text) {
		# Write-Host "$(create-Indents $currentLine.indentLevel)$text" -ForegroundColor Cyan
	}
	writein $currentLine.text
	writein "- $($lines.Count) remaining"
	$nextLine, $otherLines = $lines
	if(-not $currentLine) {
		return @{
			nodes = @()
			remaining = @()
		}
	}
	$node = @{
		line = $currentLine
		indentLevel = $currentLine.indentLevel
		text = $currentLine.text
	}
	if(-not $nextLine -or $nextLine.indentLevel -lt $currentLine.indentLevel) {
		$node.children = @()
		writein "- done"
		return @{
			nodes = @($node)
			remaining = $lines
		}
	}
	if($nextLine.indentLevel -eq $currentLine.indentLevel) {
		writein "- going over"
		$siblingsTree = parse-Tree $nextLine $otherLines
		writein "- adding $($siblingsTree.nodes.Count) siblings to $($node.text)"
		return @{
			nodes = @($node) + $siblingsTree.nodes
			remaining = $siblingsTree.remaining
		}
	}
	if($nextLine.indentLevel -gt $currentLine.indentLevel) {
		writein "- going down"
		$nextTree = parse-Tree $nextLine $otherLines
		writein "- adding $($nextTree.nodes.Count) children to $($node.text)"
		$node.children = $nextTree.nodes

		#todo - this can be slicker as it basically just repeats the above
		$nextLine, $otherLines = $nextTree.remaining
		if($nextLine.indentLevel -eq $currentLine.indentLevel){
			writein "- going over"
			$siblingsTree = parse-Tree $nextLine $otherLines
			writein "- adding $($siblingsTree.nodes.Count) siblings to $($node.text)"
			return @{
				nodes = @($node) + $siblingsTree.nodes
				remaining = $siblingsTree.remaining
			}
		}
		if(-not $nextLine -or $nextLine.indentLevel -lt $currentLine.indentLevel) {
			writein "- done"
			return @{
				nodes = @($node)
				remaining = @($nextLine) + $otherLines
			}
		}
	}
}
function visitLast($node, [scriptblock]$fn) {
	if(-not $node) {
		return
	}
	foreach($child in $node.children){
		visitLast $child $fn
	}
	&$fn $node
}
function visitFirst($node, [scriptblock]$fn, $acc) {
	if(-not $node) {
		return
	}
	&$fn $node $acc
	foreach($child in $node.children){
		visitFirst $child $fn $acc
	}
}

$head, $tail = $lines
$parsed = parse-Tree $head $tail

function parse-nodeText($node) {
	$parts = @( $node.text -split ',' | % { $_.Trim() } )
	if($parts[0] -match '^(\d+)\s*(-\s*(\d+))?') {
		$node.item = $parts[1]
		$node.description = $parts[2]
		if($node.children) {
			Write-Warning "Line has an estimate and children - ignoring children sum. '$($node.line.text)'"
		}
		$node.estimate = [int]$matches[1],[int]$matches[1]
		if($matches.Count -eq 4) {
			$node.estimate[1] = [int]$matches[3]
		}
	} else {
		$node.item = $parts[0]
		$node.description = $parts[1]
		$node.estimate = $null,$null
		if(-not $node.children) {
			Write-Warning "no estimate on leaf '$($node.text)'"
		}
		foreach($child in $node.children) {
			$node.estimate[0] += $child.estimate[0]
			$node.estimate[1] += $child.estimate[1]
		}
	}
}

foreach($node in $parsed.nodes) {
	visitLast $node ${function:parse-nodeText}
}

function create-OutputItem($node, $acc) {
	$hash = [ordered]@{
		min = $node.estimate[0]
		max = $node.estimate[1]
		item = "$(create-Indents $node.indentLevel)$($node.item)"
		description = $node.description
	}
	$acc.Add( (New-Object PsObject -property $hash) ) | out-null
}
$outgoingItems = new-object System.Collections.ArrayList
foreach($node in $parsed.nodes) {
	visitFirst $node ${function:create-OutputItem} $outgoingItems
}
return $outgoingItems