package cli

import (
	"errors"
	"fmt"
	"io"
	"os"
	"time"

	"github.com/spf13/afero"
	"github.com/urfave/cli/v2"
	"sneak.berlin/go/mfer/internal/log"
	"sneak.berlin/go/mfer/mfer"
)

// Command and flag names shared across command definitions and tests.
const (
	cmdGenerate = "generate"
	cmdCheck    = "check"
	cmdFreshen  = "freshen"
	cmdExport   = "export"
	cmdFetch    = "fetch"
	cmdVersion  = "version"

	flagProgress         = "progress"
	flagTimeout          = "timeout"
	flagDest             = "dest"
	flagRequireSignature = "require-signature"

	manifestArgsUsage = "[manifest file]"

	// defaultManifestName is the filename gen writes by default, the one
	// looked for when a command is given a directory, and the one fetch
	// appends to a directory URL.
	defaultManifestName = "index.mf"
)

// manifestTempPath returns the temp file gen and freshen write a manifest
// to before renaming it to out.
func manifestTempPath(out string) string {
	return out + ".tmp"
}

// errUnknownCommand indicates an unrecognized command argument.
var errUnknownCommand = errors.New("unknown command")

// CLIApp is the main CLI application container. It holds configuration,
// I/O streams, and filesystem abstraction to enable testing and flexibility.
//
//nolint:revive // established name used throughout the codebase and tests
type CLIApp struct {
	appname     string
	version     string
	gitrev      string
	startupTime time.Time
	exitCode    int
	app         *cli.App

	Stdin  io.Reader // Standard input stream
	Stdout io.Writer // Standard output stream for normal output
	Stderr io.Writer // Standard error stream for diagnostics
	Fs     afero.Fs  // Filesystem abstraction for all file operations
}

const banner = `
     ___           ___         ___           ___
    /__/\         /  /\       /  /\         /  /\
   |  |::\       /  /:/_     /  /:/_       /  /::\
   |  |:|:\     /  /:/ /\   /  /:/ /\     /  /:/\:\
 __|__|:|\:\   /  /:/ /:/  /  /:/ /:/_   /  /:/~/:/
/__/::::| \:\ /__/:/ /:/  /__/:/ /:/ /\ /__/:/ /:/___
\  \:\~~\__\/ \  \:\/:/   \  \:\/:/ /:/ \  \:\/:::::/
 \  \:\        \  \::/     \  \::/ /:/   \  \::/~~~~
  \  \:\        \  \:\      \  \:\/:/     \  \:\
   \  \:\        \  \:\      \  \::/       \  \:\
    \__\/         \__\/       \__\/         \__\/`

// VersionString returns the version and git revision formatted for display.
func (mfa *CLIApp) VersionString() string {
	if mfa.gitrev != "" {
		return fmt.Sprintf("%s (%s)", mfer.Version, mfa.gitrev)
	}

	return mfer.Version
}

// printVersion writes the version line shared by the --version flag and the
// version subcommand, so both produce identical output.
func (mfa *CLIApp) printVersion() {
	_, _ = fmt.Fprintf(mfa.Stdout, "%s version %s\n", mfa.appname, mfa.VersionString())
}

func (mfa *CLIApp) printBanner() {
	if log.GetLevel() <= log.InfoLevel {
		_, _ = fmt.Fprintln(mfa.Stdout, banner)
		_, _ = fmt.Fprintf(mfa.Stdout,
			"        mfer by @sneak: v%s released %s\n",
			mfer.Version, mfer.ReleaseDate)
		_, _ = fmt.Fprintln(mfa.Stdout, "            https://sneak.berlin/go/mfer")
	}
}

// setVerbosity sets the log level from -v and -q, given before the subcommand
// name (the root's copies), after it (the subcommand's own copies), or both.
// urfave/cli reads a flag from the nearest command that defines it, so each
// command in the lineage is asked. The highest -v count wins rather than the
// sum, because a subcommand without its own copies reads the root's.
func (mfa *CLIApp) setVerbosity(c *cli.Context) {
	_, present := os.LookupEnv("MFER_DEBUG")

	verbosity := 0
	quiet := false

	for _, ctx := range c.Lineage() {
		verbosity = max(verbosity, ctx.Count("verbose"))
		quiet = quiet || ctx.Bool("quiet")
	}

	switch {
	case present:
		log.EnableDebugLogging()
	case quiet:
		log.SetLevel(log.ErrorLevel)
	default:
		log.SetLevelFromVerbosity(verbosity)
	}
}

// commonFlags returns the -v and -q flags taken by the root and by the
// generate, check, freshen and fetch subcommands.
func commonFlags() []cli.Flag {
	return []cli.Flag{
		&cli.BoolFlag{
			Name:    "verbose",
			Aliases: []string{"v"},
			Usage:   "Increase verbosity (-v for verbose, -v -v for debug)",
			Count:   new(int),
		},
		&cli.BoolFlag{
			Name:    "quiet",
			Aliases: []string{"q"},
			Usage:   "Suppress output except errors",
		},
	}
}

// requireSignatureFlag returns the --require-signature flag taken by the
// check and fetch subcommands.
func requireSignatureFlag() *cli.StringFlag {
	return &cli.StringFlag{
		Name:    flagRequireSignature,
		Aliases: []string{"S"},
		Usage:   "Require manifest to be signed by the specified GPG key ID",
		EnvVars: []string{"MFER_REQUIRE_SIGNATURE"},
	}
}

func (mfa *CLIApp) generateCommand() *cli.Command {
	return &cli.Command{
		Name:      cmdGenerate,
		Aliases:   []string{"gen"},
		Usage:     "Generate manifest file",
		ArgsUsage: "[path ...]",
		Action: func(c *cli.Context) error {
			mfa.setVerbosity(c)
			mfa.printBanner()

			return mfa.generateManifestOperation(c)
		},
		Flags: append(commonFlags(),
			&cli.BoolFlag{
				Name:    "follow-symlinks",
				Aliases: []string{"L"},
				Usage:   "Resolve encountered symlinks",
			},
			&cli.BoolFlag{
				Name:    "include-dotfiles",
				Aliases: []string{"IncludeDotfiles"},

				Usage: "Include dot (hidden) files (excluded by default)",
			},
			&cli.StringFlag{
				Name:    "output",
				Value:   defaultManifestName,
				Aliases: []string{"o"},
				Usage:   "Specify output filename",
			},
			&cli.BoolFlag{
				Name:    "force",
				Aliases: []string{"f"},
				Usage:   "Overwrite output file if it exists",
			},
			&cli.BoolFlag{
				Name:    flagProgress,
				Aliases: []string{"P"},
				Usage:   "Show progress during enumeration and scanning",
			},
			&cli.StringFlag{
				Name:    "sign-key",
				Aliases: []string{"s"},
				Usage:   "GPG key ID to sign the manifest with",
				EnvVars: []string{"MFER_SIGN_KEY"},
			},
			&cli.StringFlag{
				Name:    "seed",
				Usage:   "Seed value for deterministic manifest UUID",
				EnvVars: []string{"MFER_SEED"},
			},
			&cli.BoolFlag{
				Name: "include-timestamps",
				Usage: "Include createdAt timestamp in manifest " +
					"(omitted by default for determinism)",
			},
		),
	}
}

func (mfa *CLIApp) checkCommand() *cli.Command {
	return &cli.Command{
		Name:      cmdCheck,
		Usage:     "Validate files using manifest file",
		ArgsUsage: manifestArgsUsage,
		Action: func(c *cli.Context) error {
			mfa.setVerbosity(c)
			mfa.printBanner()

			return mfa.checkManifestOperation(c)
		},
		Flags: append(commonFlags(),
			&cli.StringFlag{
				Name:    "base",
				Aliases: []string{"b"},
				Value:   ".",
				Usage:   "Base directory for resolving relative paths from manifest",
			},
			&cli.BoolFlag{
				Name:    flagProgress,
				Aliases: []string{"P"},
				Usage:   "Show progress during checking",
			},
			&cli.BoolFlag{
				Name:  "no-extra-files",
				Usage: "Fail, instead of warning, if files in base directory are not in manifest",
			},
			requireSignatureFlag(),
		),
	}
}

func (mfa *CLIApp) freshenCommand() *cli.Command {
	return &cli.Command{
		Name:      cmdFreshen,
		Usage:     "Update manifest with changed, new, and removed files",
		ArgsUsage: manifestArgsUsage,
		Action: func(c *cli.Context) error {
			mfa.setVerbosity(c)
			mfa.printBanner()

			return mfa.freshenManifestOperation(c)
		},
		Flags: append(commonFlags(),
			&cli.StringFlag{
				Name:    "base",
				Aliases: []string{"b"},
				Value:   ".",
				Usage:   "Base directory for resolving relative paths",
			},
			&cli.BoolFlag{
				Name:    "follow-symlinks",
				Aliases: []string{"L"},
				Usage:   "Resolve encountered symlinks",
			},
			&cli.BoolFlag{
				Name:    "include-dotfiles",
				Aliases: []string{"IncludeDotfiles"},

				Usage: "Include dot (hidden) files (excluded by default)",
			},
			&cli.BoolFlag{
				Name:    flagProgress,
				Aliases: []string{"P"},
				Usage:   "Show progress during scanning and hashing",
			},
			&cli.StringFlag{
				Name:    "sign-key",
				Aliases: []string{"s"},
				Usage:   "GPG key ID to sign the manifest with",
				EnvVars: []string{"MFER_SIGN_KEY"},
			},
			&cli.BoolFlag{
				Name: "include-timestamps",
				Usage: "Include createdAt timestamp in manifest " +
					"(omitted by default for determinism)",
			},
		),
	}
}

func (mfa *CLIApp) exportCommand() *cli.Command {
	return &cli.Command{
		Name:      cmdExport,
		Usage:     "Export manifest contents as JSON",
		ArgsUsage: "[manifest file or URL]",
		Action: func(c *cli.Context) error {
			mfa.setVerbosity(c)

			return mfa.exportManifestOperation(c)
		},
	}
}

func (mfa *CLIApp) versionCommand() *cli.Command {
	return &cli.Command{
		Name:  cmdVersion,
		Usage: "Show version",
		Action: func(_ *cli.Context) error {
			mfa.printVersion()

			return nil
		},
	}
}

func (mfa *CLIApp) listCommand() *cli.Command {
	return &cli.Command{
		Name:      "list",
		Aliases:   []string{"ls"},
		Usage:     "List files in manifest",
		ArgsUsage: manifestArgsUsage,
		Action: func(c *cli.Context) error {
			return mfa.listManifestOperation(c)
		},
		Flags: []cli.Flag{
			&cli.BoolFlag{
				Name:    "long",
				Aliases: []string{"l"},
				Usage:   "Show size and mtime",
			},
			&cli.BoolFlag{
				Name:  "print0",
				Usage: "Separate entries with NUL character (for xargs -0)",
			},
		},
	}
}

func (mfa *CLIApp) fetchCommand() *cli.Command {
	return &cli.Command{
		Name:      cmdFetch,
		Usage:     "fetch manifest and referenced files",
		ArgsUsage: "URL",
		Action: func(c *cli.Context) error {
			mfa.setVerbosity(c)
			mfa.printBanner()

			return mfa.fetchManifestOperation(c)
		},
		Flags: append(commonFlags(),
			&cli.DurationFlag{
				Name:  flagTimeout,
				Value: httpTimeout,
				Usage: "Time limit for each HTTP request, including the download " +
					"of its body",
			},
			&cli.StringFlag{
				Name:    flagDest,
				Aliases: []string{"d"},
				Value:   ".",
				Usage:   "Directory to download the files and the manifest into",
			},
			requireSignatureFlag(),
		),
	}
}

func (mfa *CLIApp) run(args []string) {
	mfa.startupTime = time.Now()

	if NoColor {
		// shoutout to rob pike who thinks it's juvenile
		log.DisableStyling()
	}

	// Configure log package to use our I/O streams
	log.SetOutput(mfa.Stdout, mfa.Stderr)
	log.Init()

	// -v means verbose, not version. urfave/cli's built-in version flag
	// claims -v by default, which made "mfer -v --version" fail to parse and
	// gave -v a different meaning at the root than on the generate, check,
	// freshen and fetch subcommands, where it means verbose. Verbose is the
	// more common meaning of -v in tools that offer both, so -v means verbose
	// at the root too and the version flag takes the capital -V.
	// VersionFlag and VersionPrinter are urfave/cli package globals; run() is
	// serialized in tests, so assigning them here is safe.
	cli.VersionFlag = &cli.BoolFlag{
		Name:    cmdVersion,
		Aliases: []string{"V"},
		Usage:   "print the version",
	}
	cli.VersionPrinter = func(_ *cli.Context) { mfa.printVersion() }

	mfa.app = &cli.App{
		Name:                 mfa.appname,
		Usage:                "Manifest generator",
		Version:              mfa.VersionString(),
		EnableBashCompletion: true,
		Writer:               mfa.Stdout,
		ErrWriter:            mfa.Stderr,
		Flags:                commonFlags(),
		Action: func(c *cli.Context) error {
			if c.Args().Len() > 0 {
				return fmt.Errorf("%w %q", errUnknownCommand, c.Args().First())
			}

			mfa.setVerbosity(c)
			mfa.printBanner()

			return cli.ShowAppHelp(c)
		},
		Commands: []*cli.Command{
			mfa.generateCommand(),
			mfa.checkCommand(),
			mfa.freshenCommand(),
			mfa.exportCommand(),
			mfa.versionCommand(),
			mfa.listCommand(),
			mfa.fetchCommand(),
		},
	}

	mfa.app.HideVersion = false

	err := mfa.app.Run(args)
	if err != nil {
		mfa.exitCode = 1

		log.Errorf("%s", err)
	}
}