Implement PullRequestProvider for Github

pkg/storage/transaction/pullrequest/github/github.go

@@ -0,0 +1,119 @@
+package github
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/fluxcd/go-git-providers/github"
+	"github.com/fluxcd/go-git-providers/gitprovider"
+	gogithub "github.com/google/go-github/v32/github"
+	"github.com/weaveworks/libgitops/pkg/storage/transaction"
+)
+
+// TODO: This package should really only depend on go-git-providers' abstraction interface
+
+var ErrProviderNotSupported = errors.New("only the Github go-git-providers provider is supported at the moment")
+
+// NewGitHubPRProvider returns a new transaction.PullRequestProvider from a gitprovider.Client.
+func NewGitHubPRProvider(c gitprovider.Client) (transaction.PullRequestProvider, error) {
+	// Make sure a Github client was passed
+	if c.ProviderID() != github.ProviderID {
+		return nil, ErrProviderNotSupported
+	}
+	return &prCreator{c}, nil
+}
+
+type prCreator struct {
+	c gitprovider.Client
+}
+
+func (c *prCreator) CreatePullRequest(ctx context.Context, spec transaction.PullRequestSpec) error {
+	// First, validate the input
+	if err := spec.Validate(); err != nil {
+		return fmt.Errorf("given PullRequestSpec wasn't valid")
+	}
+
+	// Use the "raw" go-github client to do this
+	ghClient := c.c.Raw().(*gogithub.Client)
+
+	// Helper variables
+	owner := spec.GetRepositoryRef().GetIdentity()
+	repo := spec.GetRepositoryRef().GetRepository()
+	var body *string
+	if spec.GetDescription() != "" {
+		body = gogithub.String(spec.GetDescription())
+	}
+
+	// Create the Pull Request
+	pr, _, err := ghClient.PullRequests.Create(ctx, owner, repo, &gogithub.NewPullRequest{
+		Head:  gogithub.String(spec.GetMergeBranch()),
+		Base:  gogithub.String(spec.GetMainBranch()),
+		Title: gogithub.String(spec.GetTitle()),
+		Body:  body,
+	})
+	if err != nil {
+		return err
+	}
+
+	// If spec.GetMilestone() is set, fetch the ID of the milestone
+	// Only set milestoneID to non-nil if specified
+	var milestoneID *int
+	if len(spec.GetMilestone()) != 0 {
+		milestoneID, err = getMilestoneID(ctx, ghClient, owner, repo, spec.GetMilestone())
+		if err != nil {
+			return err
+		}
+	}
+
+	// Only set assignees to non-nil if specified
+	var assignees *[]string
+	if a := spec.GetAssignees(); len(a) != 0 {
+		assignees = &a
+	}
+
+	// Only set labels to non-nil if specified
+	var labels *[]string
+	if l := spec.GetLabels(); len(l) != 0 {
+		labels = &l
+	}
+
+	// Only PATCH the PR if any of the fields were set
+	if milestoneID != nil || assignees != nil || labels != nil {
+		_, _, err := ghClient.Issues.Edit(ctx, owner, repo, pr.GetNumber(), &gogithub.IssueRequest{
+			Milestone: milestoneID,
+			Assignees: assignees,
+			Labels:    labels,
+		})
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func getMilestoneID(ctx context.Context, c *gogithub.Client, owner, repo, milestoneName string) (*int, error) {
+	// List all milestones in the repo
+	// TODO: This could/should use pagination
+	milestones, _, err := c.Issues.ListMilestones(ctx, owner, repo, &gogithub.MilestoneListOptions{
+		State: "all",
+	})
+	if err != nil {
+		return nil, err
+	}
+	// Loop through all milestones, search for one with the right name
+	for _, milestone := range milestones {
+		// Only consider a milestone with the right name
+		if milestone.GetTitle() != milestoneName {
+			continue
+		}
+		// Validate nil to avoid panics
+		if milestone.Number == nil {
+			return nil, fmt.Errorf("didn't expect milestone Number to be nil: %v", milestone)
+		}
+		// Return the Milestone number
+		return milestone.Number, nil
+	}
+	return nil, fmt.Errorf("couldn't find milestone with name: %s", milestoneName)
+}