package cmd

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"io"
	"net/http"
	"os"
	"strings"

	"github.com/spf13/cobra"
)

var (
	flagDownloadURL    string
	flagDownloadSHA256 string
	flagForce          bool
)

var downloadCmd = &cobra.Command{
	Use:   "download <key> <local-path>",
	Short: "Download a cached file; fall back to --url on cache miss",
	Args:  cobra.ExactArgs(2),
	RunE: func(cmd *cobra.Command, args []string) error {
		cli, cfg, err := client()
		if err != nil {
			return err
		}
		key, err := resolveKey(args[0], cfg)
		if err != nil {
			return err
		}
		dest := args[1]

		ctx := context.Background()
		exists, err := cli.Exists(ctx, key)
		if err != nil {
			return err
		}
		if exists {
			fmt.Fprintf(cmd.ErrOrStderr(), "Cache HIT  — %s\n", key)
			rc, err := cli.Get(ctx, key)
			if err != nil {
				return err
			}
			defer rc.Close()
			return writeWithSHA(dest, rc, flagDownloadSHA256)
		}

		fmt.Fprintf(cmd.ErrOrStderr(), "Cache MISS — %s\n", key)
		if flagDownloadURL == "" {
			return fmt.Errorf("%w: %s", ErrMissNoFallback, key)
		}
		fmt.Fprintf(cmd.ErrOrStderr(), "Fetching %s\n", flagDownloadURL)
		body, err := httpGet(flagDownloadURL)
		if err != nil {
			return err
		}
		defer body.Close()
		// Tee to a tempfile so we can verify the checksum before re-reading
		// for the upload step. Pure-streaming up to s3 + sha256 verify is
		// possible but complicates rewind on mismatch — tempfile keeps it
		// honest at the cost of one extra disk pass.
		tmp, err := os.CreateTemp("", "cacher-dl-*")
		if err != nil {
			return err
		}
		defer os.Remove(tmp.Name())
		defer tmp.Close()
		if _, err := io.Copy(tmp, body); err != nil {
			return err
		}
		if _, err := tmp.Seek(0, io.SeekStart); err != nil {
			return err
		}
		if err := writeWithSHA(dest, tmp, flagDownloadSHA256); err != nil {
			return err
		}
		// Re-open the verified destination file for upload to S3 so callers
		// see the cached file on next run.
		f, err := os.Open(dest)
		if err != nil {
			return err
		}
		defer f.Close()
		if err := cli.Put(ctx, key, f); err != nil {
			fmt.Fprintf(cmd.ErrOrStderr(), "warn: upload to S3 failed: %v\n", err)
			// Local download succeeded — don't fail the build just because
			// of an upload glitch.
			return nil
		}
		fmt.Fprintf(cmd.ErrOrStderr(), "Cached  → %s\n", key)
		return nil
	},
}

var uploadCmd = &cobra.Command{
	Use:   "upload <key> <local-path>",
	Short: "Upload a local file to the cache",
	Args:  cobra.ExactArgs(2),
	RunE: func(cmd *cobra.Command, args []string) error {
		cli, cfg, err := client()
		if err != nil {
			return err
		}
		key, err := resolveKey(args[0], cfg)
		if err != nil {
			return err
		}
		ctx := context.Background()
		if !flagForce {
			exists, err := cli.Exists(ctx, key)
			if err != nil {
				return err
			}
			if exists {
				fmt.Fprintf(cmd.ErrOrStderr(), "Skipped — %s already present (use --force to overwrite)\n", key)
				return nil
			}
		}
		f, err := os.Open(args[1])
		if err != nil {
			return err
		}
		defer f.Close()
		if err := cli.Put(ctx, key, f); err != nil {
			return err
		}
		fmt.Fprintf(cmd.ErrOrStderr(), "Uploaded → %s\n", key)
		return nil
	},
}

var existsCmd = &cobra.Command{
	Use:   "exists <key>",
	Short: "Exit 0 if key exists, 1 if missing, 2 on error",
	Args:  cobra.ExactArgs(1),
	RunE: func(cmd *cobra.Command, args []string) error {
		cli, cfg, err := client()
		if err != nil {
			return err
		}
		key, err := resolveKey(args[0], cfg)
		if err != nil {
			return err
		}
		ok, err := cli.Exists(context.Background(), key)
		if err != nil {
			return err
		}
		fmt.Fprintln(cmd.OutOrStdout(), key)
		if !ok {
			return ErrNotFound
		}
		return nil
	},
}

var listCmd = &cobra.Command{
	Use:   "list [sub-prefix]",
	Short: "List cache keys under prefix (optionally narrowed by sub-prefix)",
	Args:  cobra.MaximumNArgs(1),
	RunE: func(cmd *cobra.Command, args []string) error {
		cli, _, err := client()
		if err != nil {
			return err
		}
		sub := ""
		if len(args) == 1 {
			sub = args[0]
		}
		keys, err := cli.List(context.Background(), sub)
		if err != nil {
			return err
		}
		out := cmd.OutOrStdout()
		for _, k := range keys {
			fmt.Fprintln(out, k)
		}
		return nil
	},
}

var deleteCmd = &cobra.Command{
	Use:   "delete <key>",
	Short: "Delete a cache key (no error if missing)",
	Args:  cobra.ExactArgs(1),
	RunE: func(cmd *cobra.Command, args []string) error {
		cli, cfg, err := client()
		if err != nil {
			return err
		}
		key, err := resolveKey(args[0], cfg)
		if err != nil {
			return err
		}
		if err := cli.Delete(context.Background(), key); err != nil {
			return err
		}
		fmt.Fprintf(cmd.ErrOrStderr(), "Deleted — %s\n", key)
		return nil
	},
}

var keyCmd = &cobra.Command{
	Use:   "key <template>",
	Short: "Print the resolved key for a template (for shell scripting)",
	Long: `Resolves a key template by substituting --hash-from values for {hash}
and appending the arch suffix when --arch-suffix=true. Useful when the
same key needs to appear in multiple subsequent invocations:

  KEY=$(cacher key conformance/{hash}.tar.zst --hash-from docker/conformance.Dockerfile)
  if ! cacher docker exists "$KEY"; then
    docker build …
    cacher docker upload "$KEY" tag:latest
  fi`,
	Args: cobra.ExactArgs(1),
	RunE: func(cmd *cobra.Command, args []string) error {
		cfg, err := loadConfig()
		if err != nil {
			return err
		}
		key, err := resolveKey(args[0], cfg)
		if err != nil {
			return err
		}
		fmt.Fprintln(cmd.OutOrStdout(), key)
		return nil
	},
}

func init() {
	downloadCmd.Flags().StringVar(&flagDownloadURL, "url", "", "fallback URL when key is missing in S3")
	downloadCmd.Flags().StringVar(&flagDownloadSHA256, "sha256", "", "expected sha256 hex of the downloaded content")
	uploadCmd.Flags().BoolVar(&flagForce, "force", false, "overwrite if key already exists")

	for _, c := range []*cobra.Command{downloadCmd, uploadCmd, existsCmd, deleteCmd} {
		addS3Flags(c)
		addKeyFlags(c)
	}
	addS3Flags(listCmd)
	addS3Flags(keyCmd)
	addKeyFlags(keyCmd)

	rootCmd.AddCommand(downloadCmd, uploadCmd, existsCmd, listCmd, deleteCmd, keyCmd)
}

// writeWithSHA streams r into path; if want is non-empty, verifies the
// sha256 matches. On mismatch, the partial file is removed.
func writeWithSHA(path string, r io.Reader, want string) error {
	want = strings.ToLower(want)
	if err := os.MkdirAll(parentDir(path), 0o755); err != nil {
		return err
	}
	tmp, err := os.CreateTemp(parentDir(path), ".cacher-tmp-*")
	if err != nil {
		return err
	}
	tmpName := tmp.Name()
	defer os.Remove(tmpName) // no-op once renamed

	h := sha256.New()
	mw := io.MultiWriter(tmp, h)
	if _, err := io.Copy(mw, r); err != nil {
		tmp.Close()
		return err
	}
	if err := tmp.Close(); err != nil {
		return err
	}
	if want != "" {
		got := hex.EncodeToString(h.Sum(nil))
		if got != want {
			return fmt.Errorf("sha256 mismatch: got %s want %s", got, want)
		}
	}
	return os.Rename(tmpName, path)
}

func parentDir(path string) string {
	for i := len(path) - 1; i >= 0; i-- {
		if path[i] == '/' || path[i] == os.PathSeparator {
			return path[:i]
		}
	}
	return "."
}

func httpGet(url string) (io.ReadCloser, error) {
	resp, err := http.Get(url)
	if err != nil {
		return nil, fmt.Errorf("GET %s: %w", url, err)
	}
	if resp.StatusCode/100 != 2 {
		resp.Body.Close()
		return nil, fmt.Errorf("GET %s: HTTP %d", url, resp.StatusCode)
	}
	return resp.Body, nil
}