package verifyasset

import (
	"context"
	"fmt"
	"net/http"
	"path/filepath"

	"github.com/cli/cli/v2/pkg/iostreams"

	"github.com/cli/cli/v2/internal/ghrepo"
	"github.com/cli/cli/v2/pkg/cmd/attestation/api"
	"github.com/cli/cli/v2/pkg/cmd/attestation/artifact"
	att_io "github.com/cli/cli/v2/pkg/cmd/attestation/io"
	"github.com/cli/cli/v2/pkg/cmd/release/shared"

	"github.com/MakeNowJust/heredoc"
	"github.com/cli/cli/v2/pkg/cmdutil"
	"github.com/spf13/cobra"
)

type VerifyAssetOptions struct {
	TagName       string
	BaseRepo      ghrepo.Interface
	Exporter      cmdutil.Exporter
	AssetFilePath string
}

type VerifyAssetConfig struct {
	HttpClient  *http.Client
	IO          *iostreams.IOStreams
	Opts        *VerifyAssetOptions
	AttClient   api.Client
	AttVerifier shared.Verifier
}

func NewCmdVerifyAsset(f *cmdutil.Factory, runF func(*VerifyAssetConfig) error) *cobra.Command {
	opts := &VerifyAssetOptions{}

	cmd := &cobra.Command{
		Use:   "verify-asset [<tag>] <file-path>",
		Short: "Verify that a given asset originated from a specific GitHub Release.",
		Long: heredoc.Doc(`
			Verify that a given asset file originated from a specific GitHub Release using cryptographically signed attestations.

			## Understanding Verification

			An attestation is a claim made by GitHub regarding a release and its assets.

			## What This Command Does

			This command checks that the asset you provide matches an attestation produced by GitHub for a particular release. 
			It ensures the asset's integrity by validating:
			* The asset's digest matches the subject in the attestation
			* The attestation is associated with the specified release
		`),
		Hidden: true,
		Args:   cobra.MaximumNArgs(2),
		Example: heredoc.Doc(`
			# Verify an asset from the latest release
			$ gh release verify-asset ./dist/my-asset.zip

			# Verify an asset from a specific release tag
			$ gh release verify-asset v1.2.3 ./dist/my-asset.zip

			# Verify an asset from a specific release tag and output the attestation in JSON format
			$ gh release verify-asset v1.2.3 ./dist/my-asset.zip --format json
		`),
		RunE: func(cmd *cobra.Command, args []string) error {
			if len(args) == 2 {
				opts.TagName = args[0]
				opts.AssetFilePath = args[1]
			} else if len(args) == 1 {
				opts.AssetFilePath = args[0]
			} else {
				return cmdutil.FlagErrorf("you must specify an asset filepath")
			}

			opts.AssetFilePath = filepath.Clean(opts.AssetFilePath)

			baseRepo, err := f.BaseRepo()
			if err != nil {
				return fmt.Errorf("failed to determine base repository: %w", err)
			}
			opts.BaseRepo = baseRepo

			httpClient, err := f.HttpClient()
			if err != nil {
				return err
			}

			io := f.IOStreams
			attClient := api.NewLiveClient(httpClient, baseRepo.RepoHost(), att_io.NewHandler(io))

			attVerifier := &shared.AttestationVerifier{
				AttClient:  attClient,
				HttpClient: httpClient,
				IO:         io,
			}

			config := &VerifyAssetConfig{
				Opts:        opts,
				HttpClient:  httpClient,
				AttClient:   attClient,
				AttVerifier: attVerifier,
				IO:          io,
			}

			if runF != nil {
				return runF(config)
			}

			return verifyAssetRun(config)
		},
	}
	cmdutil.AddFormatFlags(cmd, &opts.Exporter)

	return cmd
}

func verifyAssetRun(config *VerifyAssetConfig) error {
	ctx := context.Background()
	opts := config.Opts
	baseRepo := opts.BaseRepo
	tagName := opts.TagName

	if tagName == "" {
		release, err := shared.FetchLatestRelease(ctx, config.HttpClient, baseRepo)
		if err != nil {
			return err
		}
		tagName = release.TagName
	}

	fileName := getFileName(opts.AssetFilePath)

	// Calculate the digest of the file
	fileDigest, err := artifact.NewDigestedArtifact(nil, opts.AssetFilePath, "sha256")
	if err != nil {
		return err
	}

	ref, err := shared.FetchRefSHA(ctx, config.HttpClient, baseRepo, tagName)
	if err != nil {
		return err
	}

	releaseRefDigest := artifact.NewDigestedArtifactForRelease(ref, "sha1")

	// Find attestations for the release tag SHA
	attestations, err := config.AttClient.GetByDigest(api.FetchParams{
		Digest:        releaseRefDigest.DigestWithAlg(),
		PredicateType: shared.ReleasePredicateType,
		Owner:         baseRepo.RepoOwner(),
		Repo:          baseRepo.RepoOwner() + "/" + baseRepo.RepoName(),
		// TODO: Allow this value to be set via a flag.
		// The limit is set to 100 to ensure we fetch all attestations for a given SHA.
		// While multiple attestations can exist for a single SHA,
		// only one attestation is associated with each release tag.
		Limit: 100,
	})
	if err != nil {
		return fmt.Errorf("no attestations found for tag %s (%s)", tagName, releaseRefDigest.DigestWithAlg())
	}

	// Filter attestations by tag name
	filteredAttestations, err := shared.FilterAttestationsByTag(attestations, opts.TagName)
	if err != nil {
		return fmt.Errorf("error parsing attestations for tag %s: %w", tagName, err)
	}

	if len(filteredAttestations) == 0 {
		return fmt.Errorf("no attestations found for release %s in %s/%s", tagName, baseRepo.RepoOwner(), baseRepo.RepoName())
	}

	// Filter attestations by subject digest
	filteredAttestations, err = shared.FilterAttestationsByFileDigest(filteredAttestations, fileDigest.Digest())
	if err != nil {
		return fmt.Errorf("error parsing attestations for digest %s: %w", fileDigest.DigestWithAlg(), err)
	}

	if len(filteredAttestations) == 0 {
		return fmt.Errorf("attestation for %s does not contain subject %s", tagName, fileDigest.DigestWithAlg())
	}

	// Verify attestation
	verified, err := config.AttVerifier.VerifyAttestation(releaseRefDigest, filteredAttestations[0])
	if err != nil {
		return fmt.Errorf("failed to verify attestation for tag %s: %w", tagName, err)
	}

	// If an exporter is provided with the --json flag, write the results to the terminal in JSON format
	if opts.Exporter != nil {
		return opts.Exporter.Write(config.IO, verified)
	}

	io := config.IO
	cs := io.ColorScheme()
	fmt.Fprintf(io.Out, "Calculated digest for %s: %s\n", fileName, fileDigest.DigestWithAlg())
	fmt.Fprintf(io.Out, "Resolved tag %s to %s\n", opts.TagName, releaseRefDigest.DigestWithAlg())
	fmt.Fprint(io.Out, "Loaded attestation from GitHub API\n\n")
	fmt.Fprintf(io.Out, cs.Green("%s Verification succeeded! %s is present in release %s\n"), cs.SuccessIcon(), fileName, opts.TagName)

	return nil
}

func getFileName(filePath string) string {
	// Get the file name from the file path
	_, fileName := filepath.Split(filePath)
	return fileName
}