Add github statistics script

eng/scripts/github-statistics.ps1

@@ -0,0 +1,158 @@
+param(
+    [array]$BaseRepositories = @(
+        'Azure/azure-sdk-tools'
+        'Azure/azure-sdk'
+        'Azure/azure-sdk-for-go'
+        'Azure/azure-sdk-for-net'
+        'Azure/azure-sdk-for-js'
+        'Azure/azure-sdk-for-python'
+        'Azure/azure-sdk-for-java'
+        'Azure/azure-sdk-for-rust'
+        'Azure/azure-sdk-for-c'
+        'Azure/azure-sdk-for-cpp'
+        'Azure/azure-sdk-for-ios'
+        'Azure/azure-sdk-for-android'
+        'Azure/azure-dev'
+        'Azure/typespec-azure'
+        'Microsoft/typespec'
+    ),
+    [array]$ExtraRepositories = @(
+        'Azure/azure-rest-api-specs'
+        'Azure/azure-rest-api-specs-pr'
+    ),
+    [int]$LookbackWeeks = 52,
+    [int]$Limit = 6000
+)
+
+Set-StrictMode -Version 3
+$ErrorActionPreference = 'Stop'
+$PSNativeCommandUseErrorActionPreference = $true
+
+function Get-PRHistory([array]$_repositories, [int32]$_lookbackWeeks, [int]$_limit) {
+    $calendar = New-Object System.Globalization.GregorianCalendar
+    # Set week boundaries to Sunday and first day of year. See System.Globalization.CalendarWeekRule
+    $currentWeek = $calendar.GetWeekOfYear((Get-Date), 0, 0)
+    # Set lookback to # of weeks ago starting at previous week boundary (excluding current week)
+    $_lookbackDays = $_lookbackWeeks * 7 + (get-date).DayOfWeek.value__
+    $allPRs = @()
+
+    foreach ($repo in $_repositories) {
+        $prs = gh pr list -s all --limit $_limit --json author,createdAt,mergedAt --repo $repo
+        $parsed = @($prs | ConvertFrom-Json -AsHashtable)
+        Write-Host "Found $($parsed.Length) PRs for $repo"
+        $allPRs += $parsed `
+                    | ForEach-Object {
+                        @{
+                            'author' = $_.author.login
+                            'created' = (Get-Date $_.createdAt)
+                            'merged' = ($_.mergedAt -ne $null ? (Get-Date $_.mergedAt) : $null)
+                        }
+                    }
+    }
+
+    $negativeLookback = -$_lookbackDays
+    $recentPRs = $allPRs | Where-Object { $_.created -gt ([datetime]::Now.AddDays($negativeLookback)) }
+
+    return $recentPRs
+}
+
+function incrementBucket($hash, [object]$bucketKey) {
+    # Cast key to object in case $hash is an ordered dictionary.
+    # Ordered dictionaries treat int keys as an index lookup by default
+    if ($hash.Contains([object]$bucketKey)) {
+        $hash[[object]$bucketKey] = $hash[[object]$bucketKey] + 1
+    } else {
+        $hash[[object]$bucketKey] = 1
+    }
+}
+
+function Get-DevAndPRCounts([array]$pullRequests) {
+    $weekHash = [ordered]@{}  # make ordered for ease of printing results in sequence
+    $authorHash = @{}
+
+    foreach ($pr in $pullRequests) {
+        $weekOfYear = $calendar.GetWeekOfYear($pr.created, 0, 0)
+        # Ignore current week, first week, and last week as they may be incomplete or slow and will skew the average
+        if ($weekOfYear -in @($currentWeek, 1, 52)) { continue }
+        incrementBucket $weekHash $weekOfYear
+        incrementBucket $authorHash $pr.author
+    }
+
+    $weeklySum = $weekHash.Values | Measure-Object -Sum | Select-Object -ExpandProperty Sum
+    [int]$weeklyAverage = $weeklySum / $weekHash.Keys.Count  # cast to [int] for rounding
+    $authorSum = $authorHash.Keys.Count
+
+    return $weekHash, $weeklyAverage, $authorSum
+}
+
+function Get-PRCompletionTimeHours([array]$pullRequests) {
+    $sumHours = 0
+    foreach ($pr in $pullRequests) {
+        if (!$pr.merged) {
+            continue
+        }
+        $sumHours += ($pr.merged - $pr.created).TotalHours
+    }
+
+    $averageHours = ($sumHours / $pullRequests.Count) -as [int]
+    return $averageHours, ($averageHours / 24)
+}
+
+$recentPRsBase = Get-PRHistory $BaseRepositories $LookbackWeeks $Limit
+$weekHashBase, $weeklyAverageBase, $authorSumBase = Get-DevAndPRCounts $recentPRsBase
+$completionHoursBase, $completionDaysBase = Get-PRCompletionTimeHours $recentPRsBase
+
+if ($ExtraRepositories) {
+    $recentPRsExtra = Get-PRHistory $ExtraRepositories $LookbackWeeks $Limit
+    $weekHashExtra, $weeklyAverageExtra, $authorSumExtra = Get-DevAndPRCounts $recentPRsExtra
+    $completionHoursExtra, $completionDaysExtra = Get-PRCompletionTimeHours $recentPRsExtra
+
+    $weekHashAll, $weeklyAverageAll, $authorSumAll = Get-DevAndPRCounts ($recentPRsBase + $recentPRsExtra)
+    $completionHoursAll, $completionDaysAll = Get-PRCompletionTimeHours ($recentPRsBase + $recentPRsExtra)
+}
+
+Write-Host "-> PRs per week - Base repos [week, count]"
+$msg = ""
+foreach ($key in $weekHashBase.Keys) {
+    $msg += "[$key, $($weekHashBase[[object]$key])] "
+}
+Write-Host $msg
+
+if ($ExtraRepositories) {
+    Write-Host "-> PRs per week - Extra repos [week, count]"
+    $msg = ""
+    foreach ($key in $weekHashBase.Keys) {
+        $msg += "[$key, $($weekHashExtra[[object]$key])] "
+    }
+    Write-Host $msg
+    Write-Host "-> PRs per week - All repos [week, count]"
+    $msg = ""
+    foreach ($key in $weekHashBase.Keys) {
+        $msg += "[$key, $($weekHashAll[[object]$key])] "
+    }
+    Write-Host $msg
+}
+Write-Host "-> Average PRs per week"
+Write-Host "Base repos: $weeklyAverageBase"
+if ($ExtraRepositories) {
+    Write-Host "Extra repos: $weeklyAverageExtra"
+    Write-Host "All repos: $weeklyAverageAll"
+}
+Write-Host "-> Total authors"
+Write-Host "Base repos: $authorSumBase"
+if ($ExtraRepositories) {
+    Write-Host "Extra repos: $authorSumExtra"
+    Write-Host "All repos: $authorSumAll"
+}
+Write-Host "-> Average completion time (hours)"
+Write-Host "Base repos: $completionHoursBase"
+if ($ExtraRepositories) {
+    Write-Host "Extra repos: $completionHoursExtra"
+    Write-Host "All repos: $completionHoursAll"
+}
+Write-Host "-> Average completion time (days)"
+Write-Host "Base repos: $completionDaysBase"
+if ($ExtraRepositories) {
+    Write-Host "Extra repos: $completionDaysExtra"
+    Write-Host "All repos: $completionDaysAll"
+}