// Package cli implements the mfer command-line interface.
package cli

import (
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"math"
	"path/filepath"
	"strconv"
	"strings"
	"time"

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

// fingerprintHexLen is the length of a full GPG key fingerprint in hex
// characters.
const fingerprintHexLen = 40

var (
	// errNoManifestFound indicates no manifest file was found in the
	// searched directory.
	errNoManifestFound = errors.New("no manifest found")
	// errInvalidFingerprint indicates a malformed --require-signature
	// fingerprint argument. The length is spliced in from
	// fingerprintHexLen so the two cannot drift apart.
	errInvalidFingerprint = errors.New(
		"invalid fingerprint: must be exactly " +
			strconv.Itoa(fingerprintHexLen) + " hex characters")
	// errManifestNotSigned indicates a signature was required but the
	// manifest is unsigned. It is wrapped mid-sentence so that the
	// rendered message stays exactly as mfer has always printed it.
	errManifestNotSigned = errors.New("manifest is not signed")
	// errSignerMismatch indicates the embedded signing key fingerprint
	// does not match the required signer. Its text is the mid-sentence
	// fragment of the rendered message, which users grep for in CI and
	// which must therefore not change; match it with errors.Is rather
	// than by reading it.
	errSignerMismatch = errors.New("does not match required")
)

// safeUint64 converts a non-negative int64 to uint64, clamping negative
// values to zero.
func safeUint64(n int64) uint64 {
	if n < 0 {
		return 0
	}

	return uint64(n)
}

// safeRateUint64 converts a bytes-per-second rate to uint64 for display.
//
// A rate is computed as bytes/elapsed, so it is +Inf when the elapsed
// time rounds to zero and NaN when zero bytes were processed in zero
// time. Neither has a defined conversion to uint64, and on amd64 +Inf
// converts to a number that renders as "8.0 EiB/s"; both display as zero
// instead.
func safeRateUint64(rate float64) uint64 {
	if math.IsNaN(rate) || math.IsInf(rate, 0) || rate <= 0 {
		return 0
	}

	if rate >= math.MaxUint64 {
		return math.MaxUint64
	}

	return uint64(rate)
}

// findManifest looks for a manifest file in the given directory.
// It checks for index.mf and .index.mf, returning the first one found.
func findManifest(fs afero.Fs, dir string) (string, error) {
	candidates := []string{"index.mf", ".index.mf"}
	for _, name := range candidates {
		path := filepath.Join(dir, name)

		exists, err := afero.Exists(fs, path)
		if err != nil {
			return "", err
		}

		if exists {
			return path, nil
		}
	}

	return "", fmt.Errorf(
		"%w in %s (looked for index.mf and .index.mf)", errNoManifestFound, dir)
}

// fetchManifestToTemp downloads a manifest URL to a temporary file and
// returns the temp file path. The caller is responsible for removing it.
func (mfa *CLIApp) fetchManifestToTemp(url string) (string, error) {
	rc, fetchErr := mfa.openManifestReader(url)
	if fetchErr != nil {
		return "", fetchErr
	}

	tmpFile, tmpErr := afero.TempFile(mfa.Fs, "", "mfer-manifest-*.mf")
	if tmpErr != nil {
		_ = rc.Close()

		return "", fmt.Errorf("failed to create temp file: %w", tmpErr)
	}

	tmpPath := tmpFile.Name()
	_, cpErr := io.Copy(tmpFile, rc)
	_ = rc.Close()
	_ = tmpFile.Close()

	if cpErr != nil {
		_ = mfa.Fs.Remove(tmpPath)

		return "", fmt.Errorf("failed to download manifest: %w", cpErr)
	}

	return tmpPath, nil
}

// verifyRequiredSigner enforces the --require-signature fingerprint
// against the manifest's embedded signing key.
func verifyRequiredSigner(chk *mfer.Checker, requiredSigner string) error {
	// Validate fingerprint format: must be exactly 40 hex characters
	if len(requiredSigner) != fingerprintHexLen {
		return fmt.Errorf("%w, got %d", errInvalidFingerprint, len(requiredSigner))
	}

	_, err := hex.DecodeString(requiredSigner)
	if err != nil {
		return fmt.Errorf("invalid fingerprint: must be valid hex: %w", err)
	}

	if !chk.IsSigned() {
		return fmt.Errorf("%w, but signature from %s is required",
			errManifestNotSigned, requiredSigner)
	}

	// Extract fingerprint from the embedded public key (not from the
	// signer field). This validates the key is importable and gets its
	// actual fingerprint.
	embeddedFP, err := chk.ExtractEmbeddedSigningKeyFP()
	if err != nil {
		return fmt.Errorf(
			"failed to extract fingerprint from embedded signing key: %w", err)
	}

	// Compare fingerprints - must be exact match (case-insensitive)
	if !strings.EqualFold(embeddedFP, requiredSigner) {
		return fmt.Errorf("embedded signing key fingerprint %s %w %s",
			embeddedFP, errSignerMismatch, requiredSigner)
	}

	log.Infof("manifest signature verified (signer: %s)", embeddedFP)

	return nil
}

// reportCheckProgress renders progress updates until the channel closes.
func reportCheckProgress(progress <-chan mfer.CheckStatus) {
	for status := range progress {
		if status.ETA > 0 {
			log.Progressf("Checking: %d/%d files, %s/s, ETA %s, %d failures",
				status.CheckedFiles,
				status.TotalFiles,
				humanize.IBytes(safeRateUint64(status.BytesPerSec)),
				status.ETA.Round(time.Second),
				status.Failures)
		} else {
			log.Progressf("Checking: %d/%d files, %s/s, %d failures",
				status.CheckedFiles,
				status.TotalFiles,
				humanize.IBytes(safeRateUint64(status.BytesPerSec)),
				status.Failures)
		}
	}

	log.ProgressDone()
}

// countCheckFailures consumes check results, counting and logging
// failures, then closes done.
func countCheckFailures(
	results <-chan mfer.Result, failures *int64, done chan<- struct{},
) {
	for result := range results {
		if result.Status != mfer.StatusOK {
			*failures++

			log.Infof("%s: %s (%s)", result.Status, result.Path, result.Message)
		} else {
			log.Verbosef("%s: %s", result.Status, result.Path)
		}
	}

	close(done)
}

// findExtraFiles reports files present on disk but absent from the
// manifest, counting each as a failure.
func findExtraFiles(ctx *cli.Context, chk *mfer.Checker, failures *int64) error {
	extraResults := make(chan mfer.Result, 1)
	extraDone := make(chan struct{})

	go func() {
		for result := range extraResults {
			*failures++

			log.Infof("%s: %s (%s)", result.Status, result.Path, result.Message)
		}

		close(extraDone)
	}()

	err := chk.FindExtraFiles(ctx.Context, extraResults)
	if err != nil {
		return fmt.Errorf("failed to check for extra files: %w", err)
	}

	<-extraDone

	return nil
}

// runCheck runs the manifest check with progress and result reporting
// and returns the number of failures.
func runCheck(ctx *cli.Context, chk *mfer.Checker, showProgress bool) (int64, error) {
	// Set up results channel
	results := make(chan mfer.Result, 1)

	// Set up progress channel
	var progress chan mfer.CheckStatus
	if showProgress {
		progress = make(chan mfer.CheckStatus, 1)

		go reportCheckProgress(progress)
	}

	// Process results in a goroutine
	var failures int64

	done := make(chan struct{})

	go countCheckFailures(results, &failures, done)

	// Run check
	err := chk.Check(ctx.Context, results, progress)
	if err != nil {
		return 0, fmt.Errorf("check failed: %w", err)
	}

	// Wait for results processing to complete
	<-done

	// Check for extra files if requested
	if ctx.Bool("no-extra-files") {
		err = findExtraFiles(ctx, chk, &failures)
		if err != nil {
			return 0, err
		}
	}

	return failures, nil
}

func (mfa *CLIApp) checkManifestOperation(ctx *cli.Context) error {
	log.Debug("checkManifestOperation()")

	manifestPath, err := mfa.resolveManifestArg(ctx)
	if err != nil {
		return fmt.Errorf("check: %w", err)
	}

	// URL manifests need to be downloaded to a temp file for the checker
	if isHTTPURL(manifestPath) {
		tmpPath, tmpErr := mfa.fetchManifestToTemp(manifestPath)
		if tmpErr != nil {
			return fmt.Errorf("check: %w", tmpErr)
		}

		defer func() { _ = mfa.Fs.Remove(tmpPath) }()

		manifestPath = tmpPath
	}

	basePath := ctx.String("base")
	showProgress := ctx.Bool("progress")

	log.Infof("checking manifest %s with base %s", manifestPath, basePath)

	// Create checker
	chk, err := mfer.NewChecker(manifestPath, basePath, mfa.Fs)
	if err != nil {
		return fmt.Errorf("failed to load manifest: %w", err)
	}

	// Check signature requirement
	requiredSigner := ctx.String("require-signature")
	if requiredSigner != "" {
		err = verifyRequiredSigner(chk, requiredSigner)
		if err != nil {
			return err
		}
	}

	log.Infof("manifest contains %d files, %s", chk.FileCount(),
		humanize.IBytes(safeUint64(int64(chk.TotalBytes()))))

	failures, err := runCheck(ctx, chk, showProgress)
	if err != nil {
		return err
	}

	elapsed := time.Since(mfa.startupTime).Seconds()

	rate := float64(chk.TotalBytes()) / elapsed
	if failures == 0 {
		log.Infof("checked %d files (%s) in %.1fs (%s/s): all OK",
			chk.FileCount(), humanize.IBytes(safeUint64(int64(chk.TotalBytes()))),
			elapsed, humanize.IBytes(safeRateUint64(rate)))
	} else {
		log.Infof("checked %d files (%s) in %.1fs (%s/s): %d failed",
			chk.FileCount(), humanize.IBytes(safeUint64(int64(chk.TotalBytes()))),
			elapsed, humanize.IBytes(safeRateUint64(rate)), failures)
	}

	if failures > 0 {
		mfa.exitCode = 1
	}

	return nil
}