package main

import (
	"errors"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/fatih/color"
	"github.com/haunt98/changeloguru/pkg/changelog"
	"github.com/haunt98/changeloguru/pkg/convention"
	"github.com/haunt98/changeloguru/pkg/git"
	"github.com/urfave/cli/v2"
	"golang.org/x/mod/semver"
)

const (
	name        = "changeloguru"
	description = "generate changelog from conventional commits"

	currentDir       = "."
	markdownFiletype = "md"

	defaultRepositry = currentDir
	defaultOutputDir = currentDir
	defaultFilename  = "CHANGELOG"
	defaultFiletype  = markdownFiletype
	defaultVersion   = "0.1.0"

	fromFlag       = "from"
	excludeToFlag  = "exclude-to"
	includeToFlag  = "include-to"
	versionFlag    = "version"
	repositoryFlag = "repository"
	outputDirFlag  = "output-dir"
	filenameFlag   = "filename"
	filetypeFlag   = "filetype"
	verboseFlag    = "verbose"
)

func main() {
	a := &action{
		flags: make(map[string]string),
		args:  make(map[string]string),
	}

	app := &cli.App{
		Name:        name,
		Description: description,
		Flags: []cli.Flag{
			&cli.StringFlag{
				Name:  fromFlag,
				Usage: "generate from `COMMIT`",
			},
			&cli.StringFlag{
				Name:  excludeToFlag,
				Usage: "generate to `COMMIT` (exclude that commit)",
			},
			&cli.StringFlag{
				Name:  includeToFlag,
				Usage: "generate to `COMMIT` (include that commit)",
			},
			&cli.StringFlag{
				Name:        versionFlag,
				Usage:       "`VERSION` to generate, follow Semantic Versioning, example 1.0.0",
				DefaultText: defaultVersion,
			},
			&cli.StringFlag{
				Name:        repositoryFlag,
				Usage:       "`REPOSITORY` path, example /go/src/myapp",
				DefaultText: defaultRepositry,
			},
			&cli.StringFlag{
				Name:        outputDirFlag,
				Usage:       "`OUTPUT_DIR` path, example /go/src/myapp",
				DefaultText: defaultOutputDir,
			},
			&cli.StringFlag{
				Name:        filenameFlag,
				Usage:       "output `FILENAME`",
				DefaultText: defaultFilename,
			},
			&cli.StringFlag{
				Name:        filetypeFlag,
				Usage:       "output `FILETYPE` support md (markdown)",
				DefaultText: defaultFiletype,
			},
			&cli.BoolFlag{
				Name:  verboseFlag,
				Usage: "show what is going on",
			},
		},
		Action: a.Run,
	}

	if err := app.Run(os.Args); err != nil {
		// Highlight error
		fmtErr := color.New(color.FgRed)
		fmtErr.Printf("[%s error]: ", name)
		fmt.Printf("%s\n", err.Error())
	}
}

type action struct {
	verbose bool
	flags   map[string]string
	args    map[string]string
}

func (a *action) Run(c *cli.Context) error {
	// Show help if there is nothing
	if c.NArg() == 0 && c.NumFlags() == 0 {
		return cli.ShowAppHelp(c)
	}

	// Set up
	a.getFlags(c)

	commits, err := a.getCommits()
	if err != nil {
		return err
	}
	a.log("commits %+v", commits)

	conventionalCommits := a.getConventionalCommits(commits)
	a.log("conventional commits %+v", conventionalCommits)

	if err := a.generateChangelog(conventionalCommits); err != nil {
		return err
	}

	return nil
}

func (a *action) getFlags(c *cli.Context) {
	a.verbose = c.Bool(verboseFlag)
	a.flags[fromFlag] = c.String(fromFlag)
	a.flags[excludeToFlag] = c.String(excludeToFlag)
	a.flags[includeToFlag] = c.String(includeToFlag)
	a.flags[versionFlag] = a.getFlagValue(c, versionFlag, defaultVersion)
	a.flags[repositoryFlag] = a.getFlagValue(c, repositoryFlag, defaultRepositry)
	a.flags[outputDirFlag] = a.getFlagValue(c, outputDirFlag, defaultOutputDir)
	a.flags[filenameFlag] = a.getFlagValue(c, filenameFlag, defaultFilename)
	a.flags[filetypeFlag] = a.getFlagValue(c, filetypeFlag, defaultFiletype)
}

func (a *action) getFlagValue(c *cli.Context, flag, fallback string) string {
	value := c.String(flag)
	if value == "" {
		value = fallback
	}

	return value
}

func (a *action) getCommits() ([]git.Commit, error) {
	repository := a.flags[repositoryFlag]
	a.log("repository %s", repository)

	r, err := git.NewRepository(repository)
	if err != nil {
		return nil, err
	}

	fromRev := a.flags[fromFlag]
	a.log("from revision %s", fromRev)

	excludeToRev := a.flags[excludeToFlag]
	a.log("exclude to revision %s", excludeToRev)

	includeToRev := a.flags[includeToFlag]
	a.log("include to revision %s", includeToRev)

	if excludeToRev != "" && includeToRev != "" {
		return nil, errors.New("excludeToFlag and includeToFlag can not appear same time")
	}

	if excludeToRev != "" {
		return r.LogExcludeTo(fromRev, excludeToRev)
	}

	if includeToRev != "" {
		return r.LogIncludeTo(fromRev, includeToRev)
	}

	return r.Log(fromRev)
}

func (a *action) getConventionalCommits(commits []git.Commit) []convention.Commit {
	conventionalCommits := make([]convention.Commit, 0, len(commits))
	for _, commit := range commits {
		conventionalCommit, err := convention.NewCommit(commit)
		if err != nil {
			a.log("failed to new conventional commits %+v: %s", commit, err)
			continue
		}

		conventionalCommits = append(conventionalCommits, conventionalCommit)
	}

	return conventionalCommits
}

func (a *action) generateChangelog(commits []convention.Commit) error {
	outputPath, _, filetype := a.getOutputPath()

	version, err := a.getVersion()
	if err != nil {
		return err
	}

	switch filetype {
	case markdownFiletype:
		return a.generateMarkdownChangelog(outputPath, version, commits)
	default:
		return fmt.Errorf("unknown filetype %s", filetype)
	}
}

func (a *action) getOutputPath() (string, string, string) {
	outputDir := a.flags[outputDirFlag]
	filename := a.flags[filenameFlag]
	filetype := a.flags[filetypeFlag]

	nameWithExt := filename + "." + filetype
	path := filepath.Join(outputDir, nameWithExt)
	a.log("output path %s", path)

	return path, filename, filetype
}

func (a *action) getVersion() (string, error) {
	version := a.flags[versionFlag]
	if !strings.HasPrefix(version, "v") {
		version = "v" + version
	}

	if !semver.IsValid(version) {
		return "", fmt.Errorf("invalid semver %s", version)
	}

	a.log("version %s", version)

	return version, nil
}

func (a *action) generateMarkdownChangelog(outputPath, version string, commits []convention.Commit) error {
	// If CHANGELOG file already exist
	var oldData string
	bytes, err := ioutil.ReadFile(outputPath)
	if err == nil {
		oldData = string(bytes)
	}

	markdownGenerator := changelog.NewMarkdownGenerator(oldData, version, time.Now())
	newData := markdownGenerator.Generate(commits)

	if err := ioutil.WriteFile(outputPath, []byte(newData), 0o644); err != nil {
		return fmt.Errorf("failed to write file %s: %w", outputPath, err)
	}

	return nil
}

func (a *action) log(format string, v ...interface{}) {
	if a.verbose {
		log.Printf(format, v...)
	}
}