// Copyright 2017 HootSuite Media 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.
// Modified hereafter by contributors to runatlantis/atlantis.

package events

import (
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"

	"github.com/pkg/errors"
	"github.com/runatlantis/atlantis/server/events/models"
	"github.com/runatlantis/atlantis/server/logging"
)

const workingDirPrefix = "repos"

//go:generate pegomock generate -m --use-experimental-model-gen --package mocks -o mocks/mock_working_dir.go WorkingDir
//go:generate pegomock generate -m --use-experimental-model-gen --package events WorkingDir

// WorkingDir handles the workspace on disk for running commands.
type WorkingDir interface {
	// Clone git clones headRepo, checks out the branch and then returns the
	// absolute path to the root of the cloned repo. It also returns
	// a boolean indicating if we should warn users that the branch we're
	// merging into has been updated since we cloned it.
	Clone(log logging.SimpleLogging, headRepo models.Repo, p models.PullRequest, workspace string) (string, bool, error)
	// GetWorkingDir returns the path to the workspace for this repo and pull.
	// If workspace does not exist on disk, error will be of type os.IsNotExist.
	GetWorkingDir(r models.Repo, p models.PullRequest, workspace string) (string, error)
	HasDiverged(log logging.SimpleLogging, cloneDir string) bool
	GetPullDir(r models.Repo, p models.PullRequest) (string, error)
	// Delete deletes the workspace for this repo and pull.
	Delete(r models.Repo, p models.PullRequest) error
	DeleteForWorkspace(r models.Repo, p models.PullRequest, workspace string) error
}

// FileWorkspace implements WorkingDir with the file system.
type FileWorkspace struct {
	DataDir string
	// CheckoutMerge is true if we should check out the branch that corresponds
	// to what the base branch will look like *after* the pull request is merged.
	// If this is false, then we will check out the head branch from the pull
	// request.
	CheckoutMerge bool
	// TestingOverrideHeadCloneURL can be used during testing to override the
	// URL of the head repo to be cloned. If it's empty then we clone normally.
	TestingOverrideHeadCloneURL string
	// TestingOverrideBaseCloneURL can be used during testing to override the
	// URL of the base repo to be cloned. If it's empty then we clone normally.
	TestingOverrideBaseCloneURL string
	// GithubAppEnabled is true if we should fetch the ref "pull/PR_NUMBER/head"
	// from the "origin" remote. If this is false, we fetch "+refs/heads/$HEAD_BRANCH"
	// from the "head" remote.
	GithubAppEnabled bool
	// use the global setting without overriding
	GpgNoSigningEnabled bool
}

// Clone git clones headRepo, checks out the branch and then returns the absolute
// path to the root of the cloned repo. It also returns
// a boolean indicating if we should warn users that the branch we're
// merging into has been updated since we cloned it.
//If the repo already exists and is at
// the right commit it does nothing. This is to support running commands in
// multiple dirs of the same repo without deleting existing plans.
func (w *FileWorkspace) Clone(
	log logging.SimpleLogging,
	headRepo models.Repo,
	p models.PullRequest,
	workspace string) (string, bool, error) {
	cloneDir := w.cloneDir(p.BaseRepo, p, workspace)

	// If the directory already exists, check if it's at the right commit.
	// If so, then we do nothing.
	if _, err := os.Stat(cloneDir); err == nil {
		log.Debug("clone directory %q already exists, checking if it's at the right commit", cloneDir)

		// We use git rev-parse to see if our repo is at the right commit.
		// If just checking out the pull request branch, we can use HEAD.
		// If doing a merge, then HEAD won't be at the pull request's HEAD
		// because we'll already have performed a merge. Instead, we'll check
		// HEAD^2 since that will be the commit before our merge.
		pullHead := "HEAD"
		if w.CheckoutMerge {
			pullHead = "HEAD^2"
		}
		revParseCmd := exec.Command("git", "rev-parse", pullHead) // #nosec
		revParseCmd.Dir = cloneDir
		outputRevParseCmd, err := revParseCmd.CombinedOutput()
		if err != nil {
			log.Warn("will re-clone repo, could not determine if was at correct commit: %s: %s: %s", strings.Join(revParseCmd.Args, " "), err, string(outputRevParseCmd))
			return cloneDir, false, w.forceClone(log, cloneDir, headRepo, p)
		}
		currCommit := strings.Trim(string(outputRevParseCmd), "\n")

		// We're prefix matching here because BitBucket doesn't give us the full
		// commit, only a 12 character prefix.
		if strings.HasPrefix(currCommit, p.HeadCommit) {
			log.Debug("repo is at correct commit %q so will not re-clone", p.HeadCommit)
			return cloneDir, w.warnDiverged(log, p, headRepo, cloneDir), nil
		}

		log.Debug("repo was already cloned but is not at correct commit, wanted %q got %q", p.HeadCommit, currCommit)
		// We'll fall through to re-clone.
	}

	// Otherwise we clone the repo.
	return cloneDir, false, w.forceClone(log, cloneDir, headRepo, p)
}

// warnDiverged returns true if we should warn the user that the branch we're
// merging into has diverged from what we currently have checked out.
// This matters in the case of the merge checkout strategy because after
// cloning the repo and doing the merge, it's possible master was updated.
// Then users won't be getting the merge functionality they expected.
// If there are any errors we return false since we prefer things to succeed
// vs. stopping the plan/apply.
func (w *FileWorkspace) warnDiverged(log logging.SimpleLogging, p models.PullRequest, headRepo models.Repo, cloneDir string) bool {
	if !w.CheckoutMerge {
		// It only makes sense to warn that master has diverged if we're using
		// the checkout merge strategy. If we're just checking out the branch,
		// then it doesn't matter what's going on with master because we've
		// decided to always run off the branch.
		return false
	}

	// Bring our remote refs up to date.
	// Reset the URL in case we are using github app credentials since these might have
	// expired and refreshed and the URL would now be different.
	// In this case, we should be using a proxy URL which substitutes the credentials in
	// as a long term fix, but something like that requires more e2e testing/time
	cmds := [][]string{
		{
			"git", "remote", "set-url", "origin", p.BaseRepo.CloneURL,
		},
		{
			"git", "remote", "set-url", "head", headRepo.CloneURL,
		},
		{
			"git", "remote", "update",
		},
	}

	for _, args := range cmds {
		cmd := exec.Command(args[0], args[1:]...) // nolint: gosec
		cmd.Dir = cloneDir

		output, err := cmd.CombinedOutput()

		if err != nil {
			log.Warn("getting remote update failed: %s", string(output))
			return false
		}
	}

	hasDiverged := w.HasDiverged(log, cloneDir)
	if hasDiverged {
		log.Info("remote master branch is ahead and thereby has new commits, it is recommended to pull new commits")
	} else {
		log.Debug("remote master branch has no new commits")
	}
	return hasDiverged
}

func (w *FileWorkspace) HasDiverged(log logging.SimpleLogging, cloneDir string) bool {
	if !w.CheckoutMerge {
		// Both the diverged warning and the UnDiverged apply requirement only apply to merge checkout strategy so
		// we assume false here for 'branch' strategy.
		return false
	}
	// Check if remote master branch has diverged.
	statusUnoCmd := exec.Command("git", "status", "--untracked-files=no")
	statusUnoCmd.Dir = cloneDir
	outputStatusUno, err := statusUnoCmd.CombinedOutput()
	if err != nil {
		log.Warn("getting repo status has failed: %s", string(outputStatusUno))
		return false
	}
	hasDiverged := strings.Contains(string(outputStatusUno), "have diverged")
	return hasDiverged
}

func (w *FileWorkspace) forceClone(log logging.SimpleLogging,
	cloneDir string,
	headRepo models.Repo,
	p models.PullRequest) error {

	err := os.RemoveAll(cloneDir)
	if err != nil {
		return errors.Wrapf(err, "deleting dir %q before cloning", cloneDir)
	}

	// Create the directory and parents if necessary.
	log.Info("creating dir %q", cloneDir)
	if err := os.MkdirAll(cloneDir, 0700); err != nil {
		return errors.Wrap(err, "creating new workspace")
	}

	// During testing, we mock some of this out.
	headCloneURL := headRepo.CloneURL
	if w.TestingOverrideHeadCloneURL != "" {
		headCloneURL = w.TestingOverrideHeadCloneURL
	}
	baseCloneURL := p.BaseRepo.CloneURL
	if w.TestingOverrideBaseCloneURL != "" {
		baseCloneURL = w.TestingOverrideBaseCloneURL
	}

	var cmds [][]string
	if w.CheckoutMerge {
		// NOTE: We can't do a shallow clone when we're merging because we'll
		// get merge conflicts if our clone doesn't have the commits that the
		// branch we're merging branched off at.
		// See https://groups.google.com/forum/#!topic/git-users/v3MkuuiDJ98.
		fetchRef := fmt.Sprintf("+refs/heads/%s:", p.HeadBranch)
		fetchRemote := "head"
		if w.GithubAppEnabled {
			fetchRef = fmt.Sprintf("pull/%d/head:", p.Num)
			fetchRemote = "origin"
		}
		cmds = [][]string{
			{
				"git", "clone", "--branch", p.BaseBranch, "--single-branch", baseCloneURL, cloneDir,
			},
			{
				"git", "remote", "add", "head", headCloneURL,
			},
			{
				"git", "fetch", fetchRemote, fetchRef,
			},
		}
		if w.GpgNoSigningEnabled {
			cmds = append(cmds, []string{
				"git", "config", "--local", "commit.gpgsign", "false",
			})
		}
		// We use --no-ff because we always want there to be a merge commit.
		// This way, our branch will look the same regardless if the merge
		// could be fast forwarded. This is useful later when we run
		// git rev-parse HEAD^2 to get the head commit because it will
		// always succeed whereas without --no-ff, if the merge was fast
		// forwarded then git rev-parse HEAD^2 would fail.
		cmds = append(cmds, []string{
			"git", "merge", "-q", "--no-ff", "-m", "atlantis-merge", "FETCH_HEAD",
		})
	} else {
		cmds = [][]string{
			{
				"git", "clone", "--branch", p.HeadBranch, "--depth=1", "--single-branch", headCloneURL, cloneDir,
			},
		}
	}

	for _, args := range cmds {
		cmd := exec.Command(args[0], args[1:]...) // nolint: gosec
		cmd.Dir = cloneDir
		// The git merge command requires these env vars are set.
		cmd.Env = append(os.Environ(), []string{
			"EMAIL=atlantis@runatlantis.io",
			"GIT_AUTHOR_NAME=atlantis",
			"GIT_COMMITTER_NAME=atlantis",
		}...)

		cmdStr := w.sanitizeGitCredentials(strings.Join(cmd.Args, " "), p.BaseRepo, headRepo)
		output, err := cmd.CombinedOutput()
		sanitizedOutput := w.sanitizeGitCredentials(string(output), p.BaseRepo, headRepo)
		if err != nil {
			sanitizedErrMsg := w.sanitizeGitCredentials(err.Error(), p.BaseRepo, headRepo)
			return fmt.Errorf("running %s: %s: %s", cmdStr, sanitizedOutput, sanitizedErrMsg)
		}
		log.Debug("ran: %s. Output: %s", cmdStr, strings.TrimSuffix(sanitizedOutput, "\n"))
	}
	return nil
}

// GetWorkingDir returns the path to the workspace for this repo and pull.
func (w *FileWorkspace) GetWorkingDir(r models.Repo, p models.PullRequest, workspace string) (string, error) {
	repoDir := w.cloneDir(r, p, workspace)
	if _, err := os.Stat(repoDir); err != nil {
		return "", errors.Wrap(err, "checking if workspace exists")
	}
	return repoDir, nil
}

// GetPullDir returns the dir where the workspaces for this pull are cloned.
// If the dir doesn't exist it will return an error.
func (w *FileWorkspace) GetPullDir(r models.Repo, p models.PullRequest) (string, error) {
	dir := w.repoPullDir(r, p)
	if _, err := os.Stat(dir); err != nil {
		return "", err
	}
	return dir, nil
}

// Delete deletes the workspace for this repo and pull.
func (w *FileWorkspace) Delete(r models.Repo, p models.PullRequest) error {
	return os.RemoveAll(w.repoPullDir(r, p))
}

// DeleteForWorkspace deletes the working dir for this workspace.
func (w *FileWorkspace) DeleteForWorkspace(r models.Repo, p models.PullRequest, workspace string) error {
	return os.RemoveAll(w.cloneDir(r, p, workspace))
}

func (w *FileWorkspace) repoPullDir(r models.Repo, p models.PullRequest) string {
	return filepath.Join(w.DataDir, workingDirPrefix, r.FullName, strconv.Itoa(p.Num))
}

func (w *FileWorkspace) cloneDir(r models.Repo, p models.PullRequest, workspace string) string {
	return filepath.Join(w.repoPullDir(r, p), workspace)
}

// sanitizeGitCredentials replaces any git clone urls that contain credentials
// in s with the sanitized versions.
func (w *FileWorkspace) sanitizeGitCredentials(s string, base models.Repo, head models.Repo) string {
	baseReplaced := strings.Replace(s, base.CloneURL, base.SanitizedCloneURL, -1)
	return strings.Replace(baseReplaced, head.CloneURL, head.SanitizedCloneURL, -1)
}