BuildTools.psm1

# Copyright(c) 2016 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may not
# use this file except in compliance with the License. You may obtain a copy of
# the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations under
# the License.

##############################################################################
# HOW TO USE THE FUNCTIONS IN THIS MODULE
##############################################################################
<#

PS ...> Import-Module .\BuildTools.psm1
WARNING: The names of some imported commands from the module 'BuildTools' include unapproved verbs that might make them less 
discoverable. To find the commands with unapproved verbs, run the Import-Module command again with the Verbose parameter. For
 a list of approved verbs, type Get-Verb.
PS ...> cd .\aspnet\2-structured-data
PS ...\aspnet\2-structured-data> Run-TestScripts
...
0 SUCCEEDED
2 FAILED
.\runTestsWithDatastore.ps1
.\runTestsWithSql.ps1

# Oh no!  My tests failed.  I forgot to update the Web.Configs from my
# environment variables.
PS ...\aspnet\2-structured-data> Update-Config
.\Web.config is modified.  Overwrite? [Y]es, [N]o, Yes to [A]ll: a
C:\Users\Jeffrey Rennie\gitrepos\getting-started-dotnet\aspnet\2-structured-data\Web.config
C:\Users\Jeffrey Rennie\gitrepos\getting-started-dotnet\aspnet\2-structured-data\Views\Web.config

# And run the tests again.
PS ...\aspnet\2-structured-data> Run-TestScripts
...
2 SUCCEEDED
.\runTestsWithDatastore.ps1
.\runTestsWithSql.ps1
0 FAILED

# Yay!  They succeeded.
# I can also just run any test script directly:
PS ...\aspnet\2-structured-data> .\runTestsWithDatastore.ps1
...
PASS 4 tests executed in 10.671s, 4 passed, 0 failed.

# Or, I can run the test and leave IISExpress running to debug:
PS ...\aspnet\2-structured-data> Set-BookStore mysql
PS ...\aspnet\2-structured-data> Run-IISExpressTest -LeaveRunning

# Don't submit the changes to Web.configs.
PS ...\aspnet\2-structured-data> Unstage-Config
Unstaged changes after reset:
M	aspnet/2-structured-data/Views/Web.config
M	aspnet/2-structured-data/Web.config

# Submit my changes.
PS ...\aspnet\2-structured-data>git commit

# Clean up, cause I'm done.
PS ...\aspnet\2-structured-data> Revert-Config

#>

##############################################################################
#.SYNOPSIS
# Adds a setting to a Web.config configuration.
#
#.PARAMETER Config
# The root xml object from a Web.config or App.config file.
#
#.PARAMETER Key
# The name of the key to set.
#
#.PARAMETER Value
# The value to set.
#
#.EXAMPLE
# Add-Setting $config 'GoogleCloudSamples:ProjectId' $env:GoogleCloudSamples:ProjectId
##############################################################################
function Add-Setting($Config, [string]$Key, [string]$Value) {
    $x = Select-Xml -Xml $Config.Node -XPath "appSettings/add[@key='$Key']"
    if ($x) {
        $x.Node.value = $Value
    }
}

##############################################################################
#.SYNOPSIS
# Logical operator.
#
#.DESCRIPTION
# When anything in pipelined to the function, outputs the inputs.
# Otherwise, evaluates the script block and returns the result. 
#
#.PARAMETER ScriptBlock
# The script block to execute if $input is empty.
##############################################################################
function When-Empty($Target, $ArgList, [ScriptBlock]$ScriptBlock) {
    if ($Target) {
        @($Target) + $ArgList
    } elseif ($ArgList) {
        $ArgList
    } else {
        &$ScriptBlock
    }
}

##############################################################################
#.SYNOPSIS
# Finds all the Web.config files in subdirectories.
#
##############################################################################
filter Get-Config ($Target, $ArgList, $Mask="Web.config") {
    $paths = When-Empty $Target $ArgList {Find-Files -Masks $Mask}
    if ($paths) {
        $paths | Resolve-Path -Relative
    }
}

##############################################################################
#.SYNOPSIS
# Updates Web.config files, pulling values from environment variables.
#
#.DESCRIPTION
# Asks the user before overwriting files that have already been modified.
# Don't forget to Revert-Config or Unstage-Config before 'git commit'ing!
#
#.PARAMETER Yes
# Never ask the user if they want to overwrite a modified Web.config.  Just
# overwrite it.
#
#.INPUTS
# Paths to Web.config.  If empty, recursively searches directories for
# Web.config files.
#
#.OUTPUTs
# Paths to Web.configs that this function modified.
#
#.EXAMPLE
# Update-Config 
##############################################################################
filter Update-Config ([switch]$Yes) {        
    $configs = Get-Config $_ $args
    foreach($configPath in $configs) {
        if (-not $Yes -and (git status -s $configPath)) {
            do {
                $reply = Read-Host "$configPath is modified.  Overwrite? [Y]es, [N]o, Yes to [A]ll"
            } until ("y", "n", "a" -contains $reply)
            if ("n" -eq $reply) { continue }
            if ("a" -eq $reply) { $Yes = $true }
        }
        $config = Select-Xml -Path $configPath -XPath configuration
        if (-not $config) {
            continue;
        }
        Add-Setting $config 'GoogleCloudSamples:BookStore' $env:GoogleCloudSamples:BookStore
        Add-Setting $config 'GoogleCloudSamples:ProjectId' $env:GoogleCloudSamples:ProjectId
        Add-Setting $config 'GoogleCloudSamples:BucketName' $env:GoogleCloudSamples:BucketName
        Add-Setting $config 'GoogleCloudSamples:AuthClientId' $env:GoogleCloudSamples:AuthClientId
        Add-Setting $config 'GoogleCloudSamples:AuthClientSecret' $env:GoogleCloudSamples:AuthClientSecret
        $connectionString = Select-Xml -Xml $config.Node -XPath "connectionStrings/add[@name='LocalMySqlServer']"
        if ($connectionString) {
            if ($env:GoogleCloudSamples:ConnectionStringCloudSql) {
                $connectionString.Node.connectionString = $env:GoogleCloudSamples:ConnectionStringCloudSql;        
            } elseif ($env:Data:MySql:ConnectionString) {
                # TODO: Stop checking this old environment variable name when we've
                # updated all the scripts.
                $connectionString.Node.connectionString = $env:Data:MySql:ConnectionString;        
            }
        }
        $connectionString = Select-Xml -Xml $config.Node -XPath "connectionStrings/add[@name='LocalSqlServer']"
        if ($connectionString) {
            if ($env:GoogleCloudSamples:ConnectionStringSqlServer) {
                $connectionString.Node.connectionString = $env:GoogleCloudSamples:ConnectionStringSqlServer;        
            } 
        }
        $config.Node.OwnerDocument.Save($config.Path);
        $config.Path
    }
}

##############################################################################
#.SYNOPSIS
# Updates Web.config files.  Sets the BookStore setting.
#
#.INPUTS
# Paths to Web.config.  If empty, recursively searches directories for
# Web.config files.
#
#.EXAMPLE
# Set-BookStore mysql
##############################################################################
filter Set-BookStore($BookStore) {
    $configs = Get-Config $_ $args
    foreach($configPath in $configs) {
        $config = Select-Xml -Path $configPath -XPath configuration
        Add-Setting $config 'GoogleCloudSamples:BookStore' $BookStore
        $config.Node.OwnerDocument.Save($config.Path)
    }
}

##############################################################################
#.SYNOPSIS
# Reverts Web.config files.
#
#.DESCRIPTION
# git must be in the current PATH.
#
#.INPUTS
# Paths to Web.config.  If empty, recursively searches directories for
# Web.config files.
##############################################################################
filter Revert-Config {
    $configs = Get-Config $_ $args
    $silent = git reset HEAD $configs
    git checkout -- $configs
}

##############################################################################
#.SYNOPSIS
# Unstages Web.config files.
#
#.DESCRIPTION
# git must be in the current PATH.
#
#.INPUTS
# Paths to Web.config.  If empty, recursively searches directories for
# Web.config files.
##############################################################################
filter Unstage-Config {
    $configs = Get-Config $_ $args
    git reset HEAD $configs
}

##############################################################################
#.SYNOPSIS
# Recursively find all the files that match a mask.
#
#.PARAMETER Path
# Start searching from where?  Defaults to the current directory.
#
#.PARAMETER Masks
# A list of masks to match against the files.
#
#.PARAMETER MaxDepth
# How deep should we look into subdirectories?  Default is no limit.
#
#.PARAMETER AntiMasks
# Stop recursing when we reach a directory with a matching name.
#
#.EXAMPLE
# Find-Files -Masks *.txt
##############################################################################
function Find-Files($Path = $null, [string[]]$Masks = '*', $MaxDepth = -1,
    $Depth=0, [string[]]$AntiMasks = @('bin', 'obj', 'packages', '.git'))
{
    foreach ($item in Get-ChildItem $Path | Sort-Object -Property Mode,Name)
    {
        if ($Masks | Where {$item -like $_})
        {
            $item.FullName
        }
        if ($AntiMasks | Where {$item -like $_})
        {
            # Do not recurse.
        }
        elseif ($MaxDepth -ge 0 -and $Depth -ge $MaxDepth)
        {
            # We have reached the max depth.  Do not recurse.
        }
        elseif (Test-Path $item.FullName -PathType Container)
        {
            Find-Files $item.FullName $Masks $MaxDepth ($Depth + 1) $AntiMasks
        }
    }
}

##############################################################################
#.SYNOPSIS
# Look for a matching file in this directory and parent directories.
#
#.PARAMETER Masks
# A list of masks to match against the files.
#
#.EXAMPLE
# UpFind-File *.txt
##############################################################################
function UpFind-File([string[]]$Masks = '*')
{    
    $dir = Get-Item .
    while (1)
    {
        foreach ($item in Get-ChildItem $dir | Sort-Object -Property Mode,Name)
        {
            if ($Masks | Where {$item -like $_})
            {
                return $item.FullName
            }
        }
        if (!$dir.parent)
        {
            return
        }
        $dir = Get-Item $dir.parent.FullName
    }    
}

##############################################################################
#.SYNOPSIS
# Runs powershell scripts and prints a summary of successes and errors.
#
#.INPUTS
# Powershell scripts.  If empty, recursively searches directories for
# scripts with 'runtests' in their names.
#
#.EXAMPLE
# Run-Tests
##############################################################################
function Run-TestScripts
{
    $scripts = When-Empty -ArgList ($input + $args) -ScriptBlock { Find-Files -Masks '*runtests*.ps1' } | Get-Item
    $rootDir = pwd
    # Keep running lists of successes and failures.
    # Array of strings: the relative path of the inner script.
    $successes = @()
    $failures = @()
    foreach ($script in $scripts) {
        $relativePath = Resolve-Path -Relative $script.FullName
        echo ("-" * 79)
        echo $relativePath
        Set-Location $script.Directory
        # A script can fail two ways.
        # 1. Throw an exception.
        # 2. The last command it executed failed. 
        Try {
            Invoke-Expression (".\" + $script.Name)
            if ($LASTEXITCODE) {
                $failures += $relativePath
            } else {
                $successes += $relativePath
            }
        }
        Catch {
            echo  $_.Exception.Message
            $failures += $relativePath
        }
        Finally {
            Set-Location $rootDir
        }
    }
    # Print a final summary.
    echo ("=" * 79)
    $successCount = $successes.Count
    echo "$successCount SUCCEEDED"
    echo $successes
    $failureCount = $failures.Count
    echo "$failureCount FAILED"
    echo $failures
    # Throw an exception to set ERRORLEVEL to 1 in the calling process.
    if ($failureCount) {
        throw "$failureCount FAILED"
    }
}

##############################################################################
#.SYNOPSIS
# Builds and runs .NET core web application in the current directory.
# Runs test using casperjs.
#
#.INPUTS
# Javascript test files to pass to casperjs.
##############################################################################
function BuildAndRun-CoreTest($TestJs = "test.js") {
    dnvm use 1.0.0-rc1-update1 -r clr
    dnu restore
    dnu build
    $webProcess = Start-Process dnx web -PassThru
    Try
    {
        Start-Sleep -Seconds 4  # Wait for web process to start up.
        casperjs $TestJs http://localhost:5000
    }
    Finally
    {
        Stop-Process $webProcess
    }
}

##############################################################################
#.SYNOPSIS
# Runs code formatter on a project or solution.
#
#.INPUTS
# .sln and .csproj files. If empty, recursively searches directories for
# project files.
#
#.EXAMPLE
# Format-Code
##############################################################################
filter Format-Code {
    $projects = When-Empty $_ $args { Find-Files -Masks *.csproj }
    foreach ($project in $projects) {
        dotnet-format -w $project
        if ($LASTEXITCODE) {
            $project.FullName
            throw "dotnet format failed with exit code $LASTEXITCODE."
        }
    }
}


##############################################################################
#.SYNOPSIS
# Runs code formatter on a project or solution.
#
#.DESCRIPTION Throws an exception if code formatter actually changed something.
#
#.INPUTS
# .sln and .csproj files. If empty, recursively searches directories for
# project files.
#
#.EXAMPLE
# Lint-Project
##############################################################################
filter Lint-Code {
    $projects = When-Empty $_ $args { Find-Files -Masks *.csproj }
    foreach ($project in $projects) {
        @($project) | Format-Code
        # If git reports a diff, codeformatter changed something, and that's bad.
        $diff = git diff
        if ($diff) {
            $diff
            throw "Lint failed for $_"
        }
    }
}

##############################################################################
#.SYNOPSIS
# Builds the .sln in the current working directory.
#
#.DESCRIPTION
# Invokes nuget first, then msbuild.  Throws an exception if nuget or the
# build fails.
##############################################################################
function Build-Solution($solution) {
    nuget restore $solution
    if ($LASTEXITCODE) {
        throw "Nuget failed with error code $LASTEXITCODE"
    }
    msbuild /p:Configuration=Debug $solution
    if ($LASTEXITCODE) {
        throw "Msbuild failed with error code $LASTEXITCODE"
    }
}

##############################################################################
#.SYNOPSIS
# Gets the port number for an IISExpress web site.
#
#.PARAMETER SiteName
# The name of the website, as listed in applicationhost.config
#
#.PARAMETER ApplicationhostConfig
# The path to applicationhost.config.
#
#.OUTPUTS
# The port number where the web site is specified to run.
##############################################################################
function Get-PortNumber($SiteName, $ApplicationhostConfig) {
    $node = Select-Xml -Path $ApplicationhostConfig `
        -XPath "/configuration/system.applicationHost/sites/site[@name='$SiteName']/bindings/binding" | 
        Select-Object -ExpandProperty Node
    $chunks = $node.bindingInformation -split ':'
    $chunks[1]
}

##############################################################################
#.SYNOPSIS
# Runs IISExpress for a web site.
#
#.PARAMETER SiteName
# The name of the website, as listed in applicationhost.config
#
#.PARAMETER ApplicationhostConfig
# The path to applicationhost.config.
#
#.OUTPUTS
# The job object
##############################################################################
function Run-IISExpress($SiteName, $ApplicationhostConfig) {
    if (!$SiteName) {
        $SiteName = (get-item -Path ".\").Name
    }
    if (!$ApplicationhostConfig) {
        $ApplicationhostConfig = UpFind-File 'applicationhost.config'
    }
    # Applicationhost.config expects the environment variable
    # GETTING_STARTED_DOTNET to point to the same directory containing
    # applicationhost.config.
    $env:GETTING_STARTED_DOTNET = `
        (Get-Item $ApplicationhostConfig).DirectoryName
    $argList = (Get-Location), ('/config:"' + $ApplicationhostConfig + '"'), `
        "/site:$SiteName", "/apppool:Clr4IntegratedAppPool", "/trace:warning"
    Start-Job { 
        Set-Location $args[0]
        iisexpress.exe  $args[1..$args.Length]
    } -ArgumentList $argList
}

##############################################################################
#.SYNOPSIS
# Run the website, then run the test javascript file with casper.
#
#.DESCRIPTION
# Throws an exception if the test fails.
#
#.PARAMETER SiteName
# The name of the website, as listed in applicationhost.config.
#
#.PARAMETER ApplicationhostConfig
# The path to applicationhost.config.  If not
# specified, searches parent directories for the file.
#
#############################################################################
function Run-IISExpressTest($SiteName = '', $ApplicationhostConfig = '', 
    $TestJs = 'test.js', [switch]$LeaveRunning = $false, [int]$TryCount=3,
    $OutputDir) {
    if (!$SiteName) {
        $SiteName = (get-item -Path ".\").Name
    }
    if (!$ApplicationhostConfig) {
        $ApplicationhostConfig = UpFind-File 'applicationhost.config'
    }

    $port = Get-PortNumber $SiteName $ApplicationhostConfig
    $webJob = Run-IISExpress $SiteName $ApplicationhostConfig
    Try
    {
        $try = 0
        while ($true) {
            Start-Sleep -Seconds 4  # Wait for web process to start up.
            $env:CASPERJS11_URL = "http://localhost:$port"
            casperjs test $TestJs --xunit=sponge_log.xml
            # Casper 1.1 always returns 0, so inspect the xml output
            # to see if a test failed.
            [xml]$x = Get-Content sponge_log.xml         
            foreach ($suite in $x.testsuites.testsuite) {
                $LASTEXITCODE += [int] $suite.failures 
            }
            if (0 -eq $LASTEXITCODE) {
                break;
            }
            if (++$try -eq $TryCount) {
                # Try no more.  Fetch a web page and dump its contents to the
                # log.  Hopefully, it will contain error information that helps
                # us debug.
                try {
                    Invoke-WebRequest http://localhost:$port/ | Write-Error
                } catch {
                    $responseStream = $_.Exception.Response.GetResponseStream()
                    $reader = New-Object System.IO.StreamReader($responseStream)
                    $reader.BaseStream.Position = 0
                    $reader.DiscardBufferedData()
                    $reader.ReadToEnd() | Write-Error
                }
                throw "Casperjs failed with error code $LASTEXITCODE"
            }
        }
    }
    Finally
    {
        if ((Test-Path sponge_log.xml) -and $OutputDir) {
            mkdir -ErrorAction SilentlyContinue $OutputDir | Out-Null
            Move-Item -Force sponge_log.xml $OutputDir
        }
        if (!$LeaveRunning) {
            Stop-Job $webJob
            Wait-Job $webJob
            Receive-Job $webJob
            Remove-Job $webJob
        }
    }
}

##############################################################################
#.SYNOPSIS
# Run the website.
#
#.PARAMTER url
# The partial url to serve.  It should contain the scheme and host.  For
# example: https://localhost:2342
#
#.RETURNS
# The job running kestrel.
##############################################################################
function Run-Kestrel([Parameter(mandatory=$true)][string]$url)
{
    $kestrelJob = Start-Job -ArgumentList (Get-Location), $url -ScriptBlock {
        Set-Location $args[0]
        $env:ASPNETCORE_URLS = $args[1]
        dotnet run
    }
    # Wait for Kestrel to come up.
    while(-not $started) {
        Start-Sleep -Seconds 1
        $lines = Receive-Job $kestrelJob
        $lines | Write-Host
        if (($kestrelJob | Get-Job).State -ne 'Running') {
            throw "Kestrel failed to start."
        }
        foreach ($line in $lines) {
            if ($line -like 'Application started.*') {
                return $kestrelJob
            }
        }
        $seconds++
        if ($seconds -gt 120) {
            throw "Kestrel took > 120 seconds to start up."
        }
    }
}

##############################################################################
#.SYNOPSIS
# Run the website, then run the test javascript file with casper.
#
#.PARAMETER PortNumber
# The port number to run the kestrel server on.
#
#.DESCRIPTION
# Throws an exception if the test fails.
#
##############################################################################
function Run-KestrelTest([Parameter(mandatory=$true)]$PortNumber, $TestJs = 'test.js', 
    [switch]$LeaveRunning = $false, [switch]$CasperJs11 = $false,
    $OutputDir) {
    $env:PORT="$PortNumber"
    $url = "http://localhost:$PortNumber"
    $job = Run-Kestrel $url
    Try
    {
        Run-CasperJs $TestJs $Url -v11:$CasperJs11
    }
    Finally
    {
        if ((Test-Path sponge_log.xml) -and $OutputDir) {
            mkdir -ErrorAction SilentlyContinue $OutputDir | Out-Null
            Move-Item -Force sponge_log.xml $OutputDir
        }
        if (!$LeaveRunning) {
            Stop-Job $job
            Receive-Job $job
            Remove-Job $job
        }
    }
}

##############################################################################
#.SYNOPSIS
# Migrate the database.
#
#.DESCRIPTION
# Must be called from a directory with a .csproj and Web.config.
#
#.PARAMETER DllName
# The name of the built binary.  Defaults to the current directory name.
# 
#.PARAMETER DllDir
# The directory containing the built binary. Defaults to standard location of 'bin'.
#
#.PARAMETER Config
# The Web.config file to use for the migration. 
# Defaults to the expected location of the Web.config file.
#
##############################################################################
function Migrate-Database($DllName = '', $DllDir = 'bin', $Config = '..\Web.config') {
    if (!$DllName) {
        # Default to the name of the current directory + .dll
        # For example, if the current directory is 3-binary-data, then the
        # dll name will be 3-binary-data.dll.
        $DllName =  (get-item .).Name + ".dll"
    }
    # Migrate.exe cannot be run in place.  It must be copied to the bin directory
    # and run from there.
    cp (Join-Path (UpFind-File packages) EntityFramework.*\tools\migrate.exe) $DllDir\.
    $originalDir = pwd
    Try {
        cd $DllDir
        .\migrate.exe $dllName /startupConfigurationFile="$Config"
        if ($LASTEXITCODE) {
            throw "migrate.exe failed with error code $LASTEXITCODE"
        }
    }
    Finally {
        cd $originalDir
    }
}

##############################
#.SYNOPSIS
# Runs CasperJs
#
#.PARAMETER TestJs
# The Javascript file to run.
#
#.PARAMETER Url
# The url to pass to the test.  Usually points to running website to test.
#
#.PARAMETER v11
# Use CasperJs version 1.1 instead of 1.0.
##############################
function Run-CasperJs($TestJs='test.js', $Url, [switch]$v11 = $false,
    [string]$OutDir) {
    if ($v11) {
        $env:CASPERJS11_URL = $Url
        # Casperjs.exe creates a new terminal window, from which we
        # cannot capture output.  So we use python to invoke it and
        # capture output.
        $casperOut = casperjs test $TestJs --xunit=sponge_log.xml
        # Casper 1.1 always returns 0, so inspect the xml output
        # to see if a test failed.
        [xml]$x = Get-Content sponge_log.xml         
        $LASTEXITCODE = 0      
        foreach ($suite in $x.testsuites.testsuite) {
            $LASTEXITCODE += [int] $suite.failures 
        }
    } else {
        $casperOut = casperjs $TestJs $Url
    }
    if ($LASTEXITCODE -eq 0) {
        $casperOut | Write-Host
        return
    }
    $casperOut | Write-Host
    throw "Casperjs failed with error code $LASTEXITCODE"
}

##############################################################################
#.SYNOPSIS
# Calls nuget update on all the packages that match the mask.
#
#.PARAMETER Mask
# Which packages should be updated?
#
#.INPUTS
# Paths to .sln files.  If empty, recursively searches directories for
# *.sln files.
#
#.EXAMPLE
# Update-Packages Google.*
##############################################################################
filter Update-Packages ([string] $Mask) {
    $solutions = When-Empty $_ $args { Find-Files -Masks *.sln }
    foreach ($solution in $solutions) {
        # Nuget refuses to update without calling restore first.
        nuget restore $solution
        # Assume all packages.configs in the same directory, or a subdirectory
        # as the solution are for projects in the solution.
        $packageConfigs = Find-Files (Get-Item $solution).Directory -Masks packages.config
        # Inspect each packages.config and find matching Ids.
        $packageIds = $packageConfigs `
            | ForEach-Object {(Select-Xml -Path $_ -XPath packages/package).Node.Id} `
            | Where {$_ -like $Mask}
        # Calling nuget update with no packageIds means update *all* packages,
        # and that's definitely not what we want.
        if ($packageIds) {
            nuget update -Prerelease $solution ($packageIds | ForEach-Object {"-Id", $_})
        }
    }
}

##############################################################################
#.SYNOPSIS
# Make a backup copy of a file, run the script, and restore the file.
#
#.PARAMETER Files
# A list of files to back up.
#
#.PARAMETER ScriptBlock
# The script to execute.
#
#.EXAMPLE
# Backup-File Program.cs { Build }
##############################################################################
function Backup-File(
    [string[]][Parameter(Mandatory=$true,ValueFromPipeline=$true)] $Files,
    [scriptblock][Parameter(Mandatory=$true)] $ScriptBlock)
{
    $fileMap = @{}
    try {
        foreach ($file in $files) {
            $tempCopy = [System.IO.Path]::GetTempFileName()
            Copy-Item -Force $file $tempCopy
            $fileMap[$file] = $tempCopy
        }
        . $ScriptBlock
    }
    finally {
        foreach ($file in $files) {
            Copy-Item -Force $fileMap[$file] $file
        }
    }
}

##############################################################################
#.SYNOPSIS
# Given a path to a runTests.ps1 script, find the git timestamp of changes in
# the same directory. 
##############################################################################
function Get-GitTimeStampForScript($script) {
    Push-Location
    try {
        Set-Location (Split-Path $script)
        $dateText = git log -n 1 --format=%cd --date=iso .
        $newestDate = @(($dateText | Get-Date).ToUniversalTime().ToString("o"))
        # Search for dependencies too.
        $references = dotnet list reference | Where-Object {Test-Path $_ }
        # Look up the timestamp for each dependency.
        foreach ($ref in $references) {
            $dateText = git log -n 1 --format=%cd --date=iso (Split-Path $ref)
            $newestDate += @(($dateText | Get-Date).ToUniversalTime().ToString("o"))
        }
        # Return a string combining all the timestamps in descending order.
        return ($newestDate | Sort-Object -Descending) -join "+"
    } finally {
        Pop-Location
    }
}