package git

import (
	"fmt"
	"io/ioutil"
	"os"
	"path/filepath"
	"regexp"
	"strings"

	"github.com/fatih/color"
	"github.com/jesseduffield/lazygit/pkg/commands"
	"github.com/jesseduffield/lazygit/pkg/utils"
	"github.com/sirupsen/logrus"
)

// context:
// here we get the commits from git log but format them to show whether they're
// unpushed/pushed/merged into the base branch or not, or if they're yet to
// be processed as part of a rebase (these won't appear in git log but we
// grab them from the rebase-related files in the .git directory to show them

// if we find out we need to use one of these functions in the git.go file, we
// can just pull them out of here and put them there and then call them from in here

// CommitListBuilder returns a list of Branch objects for the current repo
type CommitListBuilder struct {
	Log        *logrus.Entry
	GitCommand *commands.GitCommand
	OSCommand  *commands.OSCommand
}

// NewCommitListBuilder builds a new commit list builder
func NewCommitListBuilder(log *logrus.Entry, gitCommand *commands.GitCommand, osCommand *commands.OSCommand) (*CommitListBuilder, error) {
	return &CommitListBuilder{
		Log:        log,
		GitCommand: gitCommand,
		OSCommand:  osCommand,
	}, nil
}

// GetCommits obtains the commits of the current branch
func (c *CommitListBuilder) GetCommits() ([]*commands.Commit, error) {
	commits := []*commands.Commit{}
	var rebasingCommits []*commands.Commit
	rebaseMode, err := c.GitCommand.RebaseMode()
	if err != nil {
		return nil, err
	}
	if rebaseMode != "" {
		// here we want to also prepend the commits that we're in the process of rebasing
		rebasingCommits, err = c.getRebasingCommits(rebaseMode)
		if err != nil {
			return nil, err
		}
		if len(rebasingCommits) > 0 {
			commits = append(commits, rebasingCommits...)
		}
	}

	unpushedCommits := c.getUnpushedCommits()
	log := c.getLog()

	// now we can split it up and turn it into commits
	for _, line := range utils.SplitLines(log) {
		splitLine := strings.Split(line, " ")
		sha := splitLine[0]
		_, unpushed := unpushedCommits[sha]
		status := map[bool]string{true: "unpushed", false: "pushed"}[unpushed]
		commits = append(commits, &commands.Commit{
			Sha:           sha,
			Name:          strings.Join(splitLine[1:], " "),
			Status:        status,
			DisplayString: strings.Join(splitLine, " "),
		})
	}
	if rebaseMode != "" {
		currentCommit := commits[len(rebasingCommits)]
		blue := color.New(color.FgYellow)
		youAreHere := blue.Sprint("<-- YOU ARE HERE ---")
		currentCommit.Name = fmt.Sprintf("%s %s", youAreHere, currentCommit.Name)
	}
	return c.setCommitMergedStatuses(commits)
}

// getRebasingCommits obtains the commits that we're in the process of rebasing
func (c *CommitListBuilder) getRebasingCommits(rebaseMode string) ([]*commands.Commit, error) {
	switch rebaseMode {
	case "normal":
		return c.getNormalRebasingCommits()
	case "interactive":
		return c.getInteractiveRebasingCommits()
	default:
		return nil, nil
	}
}

func (c *CommitListBuilder) getNormalRebasingCommits() ([]*commands.Commit, error) {
	rewrittenCount := 0
	bytesContent, err := ioutil.ReadFile(".git/rebase-apply/rewritten")
	if err == nil {
		content := string(bytesContent)
		rewrittenCount = len(strings.Split(content, "\n"))
	}

	// we know we're rebasing, so lets get all the files whose names have numbers
	commits := []*commands.Commit{}
	err = filepath.Walk(".git/rebase-apply", func(path string, f os.FileInfo, err error) error {
		if rewrittenCount > 0 {
			rewrittenCount--
			return nil
		}
		if err != nil {
			return err
		}
		re := regexp.MustCompile(`^\d+$`)
		if !re.MatchString(f.Name()) {
			return nil
		}
		bytesContent, err := ioutil.ReadFile(path)
		if err != nil {
			return err
		}
		content := string(bytesContent)
		commit, err := c.commitFromPatch(content)
		if err != nil {
			return err
		}
		commits = append([]*commands.Commit{commit}, commits...)
		return nil
	})
	if err != nil {
		return nil, err
	}

	return commits, nil
}

// git-rebase-todo example:
// pick ac446ae94ee560bdb8d1d057278657b251aaef17 ac446ae
// pick afb893148791a2fbd8091aeb81deba4930c73031 afb8931

// git-rebase-todo.backup example:
// pick 49cbba374296938ea86bbd4bf4fee2f6ba5cccf6 third commit on master
// pick ac446ae94ee560bdb8d1d057278657b251aaef17 blah  commit on master
// pick afb893148791a2fbd8091aeb81deba4930c73031 fourth commit on master

// getInteractiveRebasingCommits takes our git-rebase-todo and our git-rebase-todo.backup files
// and extracts out the sha and names of commits that we still have to go
// in the rebase:
func (c *CommitListBuilder) getInteractiveRebasingCommits() ([]*commands.Commit, error) {
	bytesContent, err := ioutil.ReadFile(".git/rebase-merge/git-rebase-todo")
	if err != nil {
		c.Log.Info(fmt.Sprintf("error occured reading git-rebase-todo: %s", err.Error()))
		// we assume an error means the file doesn't exist so we just return
		return nil, nil
	}

	commits := []*commands.Commit{}
	lines := strings.Split(string(bytesContent), "\n")
	for _, line := range lines {
		if line == "" {
			return commits, nil
		}
		splitLine := strings.Split(line, " ")
		commits = append([]*commands.Commit{&commands.Commit{
			Sha:    splitLine[1][0:7],
			Name:   strings.Join(splitLine[2:], " "),
			Status: "rebasing",
			Action: splitLine[0],
		}}, commits...)
	}

	return nil, nil
}

// assuming the file starts like this:
// From e93d4193e6dd45ca9cf3a5a273d7ba6cd8b8fb20 Mon Sep 17 00:00:00 2001
// From: Lazygit Tester <test@example.com>
// Date: Wed, 5 Dec 2018 21:03:23 +1100
// Subject: second commit on master
func (c *CommitListBuilder) commitFromPatch(content string) (*commands.Commit, error) {
	lines := strings.Split(content, "\n")
	sha := strings.Split(lines[0], " ")[1][0:7]
	name := strings.TrimPrefix(lines[3], "Subject: ")
	return &commands.Commit{
		Sha:    sha,
		Name:   name,
		Status: "rebasing",
	}, nil
}

func (c *CommitListBuilder) setCommitMergedStatuses(commits []*commands.Commit) ([]*commands.Commit, error) {
	ancestor, err := c.getMergeBase()
	if err != nil {
		return nil, err
	}
	if ancestor == "" {
		return commits, nil
	}
	passedAncestor := false
	for i, commit := range commits {
		if strings.HasPrefix(ancestor, commit.Sha) {
			passedAncestor = true
		}
		if commit.Status != "pushed" {
			continue
		}
		if passedAncestor {
			commits[i].Status = "merged"
		}
	}
	return commits, nil
}

func (c *CommitListBuilder) getMergeBase() (string, error) {
	currentBranch, err := c.GitCommand.CurrentBranchName()
	if err != nil {
		return "", err
	}

	baseBranch := "master"
	if strings.HasPrefix(currentBranch, "feature/") {
		baseBranch = "develop"
	}

	output, err := c.OSCommand.RunCommandWithOutput(fmt.Sprintf("git merge-base HEAD %s", baseBranch))
	if err != nil {
		// swallowing error because it's not a big deal; probably because there are no commits yet
	}
	return output, nil
}

// getUnpushedCommits Returns the sha's of the commits that have not yet been pushed
// to the remote branch of the current branch, a map is returned to ease look up
func (c *CommitListBuilder) getUnpushedCommits() map[string]bool {
	pushables := map[string]bool{}
	o, err := c.OSCommand.RunCommandWithOutput("git rev-list @{u}..HEAD --abbrev-commit")
	if err != nil {
		return pushables
	}
	for _, p := range utils.SplitLines(o) {
		pushables[p] = true
	}

	return pushables
}

// getLog gets the git log (currently limited to 30 commits for performance
// until we work out lazy loading
func (c *CommitListBuilder) getLog() string {
	// currently limiting to 30 for performance reasons
	// TODO: add lazyloading when you scroll down
	result, err := c.OSCommand.RunCommandWithOutput("git log --oneline -30")
	if err != nil {
		// assume if there is an error there are no commits yet for this branch
		return ""
	}

	return result
}