// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Package issues provides a general way to interact with issues,
// and a client for interacting with the GitHub  issues API.
package issues

import (
	"context"
	"fmt"
	"time"

	"github.com/google/go-github/v41/github"
	"golang.org/x/oauth2"
	"golang.org/x/vulndb/internal/derrors"
)

// An Issue represents a GitHub issue or similar.
type Issue struct {
	Title     string
	Body      string
	Labels    []string
	CreatedAt time.Time
}

// Client is a client that can create and retrieve issues.
type Client interface {
	// Destination describes where issues will be created.
	Destination() string

	// Reference returns a string that refers to the issue with number.
	Reference(number int) string

	// IssueExists reports whether an issue with the given ID exists.
	IssueExists(ctx context.Context, number int) (bool, error)

	// CreateIssue creates a new issue.
	CreateIssue(ctx context.Context, iss *Issue) (number int, err error)

	// GetIssue returns an issue with the given issue number.
	GetIssue(ctx context.Context, number int) (iss *Issue, err error)
}

type githubClient struct {
	client *github.Client
	owner  string
	repo   string
}

// NewGitHubClient creates a Client that will create issues in
// the a GitHub repo.
// A GitHub access token is required to create issues.
func NewGitHubClient(owner, repo, accessToken string) *githubClient {
	ts := oauth2.StaticTokenSource(&oauth2.Token{AccessToken: accessToken})
	tc := oauth2.NewClient(context.Background(), ts)
	return &githubClient{
		client: github.NewClient(tc),
		owner:  owner,
		repo:   repo,
	}
}

// Destination implements Client.Destination.
func (c *githubClient) Destination() string {
	return fmt.Sprintf("https://github.com/%s/%s", c.owner, c.repo)
}

// Reference implements Client.Reference.
func (c *githubClient) Reference(num int) string {
	return fmt.Sprintf("%s/issues/%d", c.Destination(), num)
}

// IssueExists implements Client.IssueExists.
func (c *githubClient) IssueExists(ctx context.Context, number int) (_ bool, err error) {
	defer derrors.Wrap(&err, "IssueExists(%d)", number)

	iss, _, err := c.client.Issues.Get(ctx, c.owner, c.repo, number)
	if err != nil {
		return false, err
	}
	if iss != nil {
		fmt.Printf("ID = %d, Number = %d\n", iss.GetID(), iss.GetNumber())
		return true, nil
	}
	return false, nil
}

// GetIssue implements Client.GetIssue.
func (c *githubClient) GetIssue(ctx context.Context, number int) (_ *Issue, err error) {
	defer derrors.Wrap(&err, "GetIssue(%d)", number)
	iss, _, err := c.client.Issues.Get(ctx, c.owner, c.repo, number)
	if err != nil {
		return nil, err
	}
	r := &Issue{}
	if iss.Title != nil {
		r.Title = *iss.Title
	}
	if iss.Body != nil {
		r.Body = *iss.Body
	}
	if iss.CreatedAt != nil {
		r.CreatedAt = *iss.CreatedAt
	}
	return r, nil
}

// CreateIssue implements Client.CreateIssue.
func (c *githubClient) CreateIssue(ctx context.Context, iss *Issue) (number int, err error) {
	defer derrors.Wrap(&err, "CreateIssue(%s)", iss.Title)

	req := &github.IssueRequest{
		Title: &iss.Title,
		Body:  &iss.Body,
	}
	if len(iss.Labels) > 0 {
		req.Labels = &iss.Labels
	}
	giss, _, err := c.client.Issues.Create(ctx, c.owner, c.repo, req)
	if err != nil {
		return 0, err
	}
	return giss.GetNumber(), nil
}