[CmdletBinding()]
param(
    [Parameter(Mandatory = $true)]
    [string]$RepeatedSampleComparison,

    [Parameter(Mandatory = $true)]
    [string]$LongWindowComparison,

    [string]$OutputReport
)

$ErrorActionPreference = 'Stop'

function Read-ComparisonReport {
    param([string]$Path, [string]$Label)

    if (-not (Test-Path -LiteralPath $Path -PathType Leaf)) {
        throw "$Label comparison does not exist: $Path"
    }
    $report = Get-Content -Raw -Encoding UTF8 -LiteralPath $Path | ConvertFrom-Json
    if ($null -eq $report -or $null -eq $report.comparisons) {
        throw "$Label comparison has no comparisons array: $Path"
    }
    return $report
}

function Build-ComparisonIndex {
    param([object[]]$Comparisons, [string]$Label)

    $index = @{}
    foreach ($comparison in $Comparisons) {
        $key = "$($comparison.result)|$($comparison.metric)"
        if ($index.ContainsKey($key)) {
            throw "$Label comparison contains duplicate metric: $key"
        }
        $index[$key] = $comparison
    }
    return $index
}

$repeatedReport = Read-ComparisonReport `
    -Path $RepeatedSampleComparison `
    -Label 'Repeated-sample'
$longWindowReport = Read-ComparisonReport `
    -Path $LongWindowComparison `
    -Label 'Long-window'
$repeatedIndex = Build-ComparisonIndex `
    -Comparisons @($repeatedReport.comparisons) `
    -Label 'Repeated-sample'
$longWindowIndex = Build-ComparisonIndex `
    -Comparisons @($longWindowReport.comparisons) `
    -Label 'Long-window'
$repeatedKeys = @($repeatedIndex.Keys | Sort-Object)
$longWindowKeys = @($longWindowIndex.Keys | Sort-Object)
if (($repeatedKeys | ConvertTo-Json -Compress) -cne ($longWindowKeys | ConvertTo-Json -Compress)) {
    throw 'Comparison metric inventories differ between repeated and long-window protocols'
}

$repeatableRegressions = [System.Collections.Generic.List[object]]::new()
$nonRepeatableRegressions = [System.Collections.Generic.List[object]]::new()
foreach ($key in $repeatedKeys) {
    $repeatedMetricComparison = $repeatedIndex[$key]
    $longWindowMetricComparison = $longWindowIndex[$key]
    $repeatedFailed = ([bool]$repeatedMetricComparison.passed) -eq $false
    $longWindowFailed = ([bool]$longWindowMetricComparison.passed) -eq $false
    if ($repeatedFailed -and $longWindowFailed) {
        $repeatableRegressions.Add([pscustomobject]@{
            key = $key
            repeated_sample = $repeatedMetricComparison
            long_window = $longWindowMetricComparison
        })
    } elseif ($repeatedFailed -or $longWindowFailed) {
        $nonRepeatableRegressions.Add([pscustomobject]@{
            key = $key
            failed_protocol = if ($repeatedFailed) { 'repeated_sample' } else { 'long_window' }
        })
    }
}

$summary = [pscustomobject]@{
    schema_version = 1
    repeated_sample_comparison = $RepeatedSampleComparison
    long_window_comparison = $LongWindowComparison
    metric_comparisons = $repeatedKeys.Count
    passed = $repeatableRegressions.Count -eq 0
    repeatable_regressions = @($repeatableRegressions)
    non_repeatable_regressions = @($nonRepeatableRegressions)
}
if ($OutputReport) {
    $parent = Split-Path -Parent $OutputReport
    if ($parent -and -not (Test-Path -LiteralPath $parent)) {
        New-Item -ItemType Directory -Path $parent | Out-Null
    }
    $summary | ConvertTo-Json -Depth 20 | Set-Content -Encoding UTF8 -LiteralPath $OutputReport
}

if ($repeatableRegressions.Count -gt 0) {
    foreach ($regression in $repeatableRegressions) {
        Write-Error "RENDER_PERFORMANCE_STABILITY: repeatable regression $($regression.key)" -ErrorAction Continue
    }
    Write-Host "RENDER_PERFORMANCE_STABILITY FAIL repeated=$($repeatableRegressions.Count) metrics=$($repeatedKeys.Count)"
    exit 1
}

Write-Host "RENDER_PERFORMANCE_STABILITY PASS metrics=$($repeatedKeys.Count) non_repeatable=$($nonRepeatableRegressions.Count)"
exit 0