#!/usr/bin/env pwsh -c

<#
.DESCRIPTION
Creates a GitHub pull request for a given branch if it doesn't already exist
.PARAMETER RepoOwner
The GitHub repository owner to create the pull request against.
.PARAMETER RepoName
The GitHub repository name to create the pull request against.
.PARAMETER BaseBranch
The base or target branch we want the pull request to be against.
.PARAMETER PROwner
The owner of the branch we want to create a pull request for.
.PARAMETER PRBranch
The branch which we want to create a pull request for.
.PARAMETER AuthToken
A personal access token
#>
[CmdletBinding(SupportsShouldProcess = $true)]
param(
    [Parameter(Mandatory = $true)]
    $RepoOwner,

    [Parameter(Mandatory = $true)]
    $RepoName,

    [Parameter(Mandatory = $true)]
    $BaseBranch,

    [Parameter(Mandatory = $true)]
    $PROwner,

    [Parameter(Mandatory = $true)]
    $PRBranch,

    [Parameter(Mandatory = $true)]
    $AuthToken,

    [Parameter(Mandatory = $true)]
    $PRTitle,
    $PRBody = $PRTitle
)

$ErrorActionPreference = 'stop'
Set-StrictMode -Version 1
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12

$headers = @{
    Authorization = "bearer $AuthToken"
}

$query = 'query ($repoOwner: String!, $repoName: String!, $baseRefName: String!) {
    repository(owner: $repoOwner, name: $repoName) {
      pullRequests(baseRefName: $baseRefName, states: OPEN, first: 100) {
        totalCount
        nodes {
          number
          headRef {
            name
            repository {
              name
              owner {
                login
              }
            }
          }
        }
      }
    }
  }'


$data = @{
    query     = $query
    variables = @{
        repoOwner   = $RepoOwner
        repoName    = $RepoName
        baseRefName = $BaseBranch
    }
}

$resp = Invoke-RestMethod -Method Post -Headers $headers `
                          https://api.github.com/graphql `
                          -Body ($data | ConvertTo-Json)
$resp | Write-Verbose

$matchingPr = $resp.data.repository.pullRequests.nodes `
    | ? { $_.headRef.name -eq $PRBranch -and $_.headRef.repository.owner.login -eq $PROwner } `
    | select -First 1

if ($matchingPr) {
    Write-Host -f green "Pull request already exists https://github.com/$RepoOwner/$RepoName/pull/$($matchingPr.number)"
}
else {
    $data = @{
        title                 = $PRTitle
        head                  = "${PROwner}:${PRBranch}"
        base                  = $BaseBranch
        body                  = $PRBody
        maintainer_can_modify = $true
    }

    $resp = Invoke-RestMethod -Method POST -Headers $headers `
                              https://api.github.com/repos/$RepoOwner/$RepoName/pulls `
                              -Body ($data | ConvertTo-Json)
    $resp | Write-Verbose
    Write-Host -f green "Pull request created https://github.com/$RepoOwner/$RepoName/pull/$($resp.number)"
}