package cmd

import (
	"fmt"
	"runtime"

	"github.com/spf13/cobra"

	"go.bigb.es/cacher/internal/config"
	"go.bigb.es/cacher/internal/hash"
	"go.bigb.es/cacher/internal/s3"
)

// Flags overridable per command (flag > env > config > defaults).
var (
	flagEndpoint   string
	flagRegion     string
	flagBucket     string
	flagPrefix     string
	flagArchSuffix string // "true"/"false"/"" (unset)
	flagKeyFile    string
	flagSecretFile string

	// Key derivation (attached by addKeyFlags).
	flagHashFrom   []string
	flagHashLength int
)

// addKeyFlags attaches --hash-from / --hash-length. Use on every command
// that takes a <key> argument.
func addKeyFlags(c *cobra.Command) {
	c.Flags().StringSliceVar(&flagHashFrom, "hash-from", nil,
		"path(s) whose sha256 is substituted for {hash} in the key (repeatable; file or directory)")
	c.Flags().IntVar(&flagHashLength, "hash-length", hash.DefaultLength,
		"truncate the derived hash to N hex chars")
}

// resolveKey applies --hash-from and --arch-suffix to the user-supplied
// key template. With no --hash-from, the template is returned verbatim
// (plus arch suffix if enabled).
func resolveKey(keyTemplate string, cfg config.Config) (string, error) {
	var derived string
	if len(flagHashFrom) > 0 {
		var err error
		derived, err = hash.Derive(flagHashFrom, flagHashLength)
		if err != nil {
			return "", err
		}
	}
	return hash.ApplyTemplate(keyTemplate, derived, runtime.GOOS, runtime.GOARCH, cfg.ArchSuffix), nil
}

// addS3Flags attaches the standard S3 override flags to a command. Most
// commands accept them so single-shot invocations can override config.
func addS3Flags(c *cobra.Command) {
	c.Flags().StringVar(&flagEndpoint, "endpoint", "", "S3 endpoint URL (overrides config)")
	c.Flags().StringVar(&flagRegion, "region", "", "S3 region (overrides config)")
	c.Flags().StringVar(&flagBucket, "bucket", "", "S3 bucket (overrides config)")
	c.Flags().StringVar(&flagPrefix, "prefix", "", "S3 key prefix (overrides config)")
	c.Flags().StringVar(&flagArchSuffix, "arch-suffix", "", "append -<goos>-<goarch> to key (true|false; default from config)")
	c.Flags().StringVar(&flagKeyFile, "key-file", "", "path to S3 access key id file (overrides config)")
	c.Flags().StringVar(&flagSecretFile, "secret-file", "", "path to S3 secret file (overrides config)")
}

// loadConfig merges file → env → flag overrides.
func loadConfig() (config.Config, error) {
	cfg, err := config.Load(flagConfigPath)
	if err != nil {
		return cfg, err
	}
	if err := config.ApplyEnv(&cfg); err != nil {
		return cfg, err
	}
	if flagEndpoint != "" {
		cfg.Endpoint = flagEndpoint
	}
	if flagRegion != "" {
		cfg.Region = flagRegion
	}
	if flagBucket != "" {
		cfg.Bucket = flagBucket
	}
	if flagPrefix != "" {
		cfg.Prefix = flagPrefix
	}
	if flagKeyFile != "" {
		cfg.KeyFile = flagKeyFile
	}
	if flagSecretFile != "" {
		cfg.SecretFile = flagSecretFile
	}
	switch flagArchSuffix {
	case "true":
		cfg.ArchSuffix = true
	case "false":
		cfg.ArchSuffix = false
	case "":
		// inherit from file/env
	default:
		return cfg, fmt.Errorf("--arch-suffix must be true|false, got %q", flagArchSuffix)
	}
	return cfg, nil
}

// client builds a Garage-tuned S3 client from the resolved config.
func client() (*s3.Client, config.Config, error) {
	cfg, err := loadConfig()
	if err != nil {
		return nil, cfg, err
	}
	if err := cfg.Validate(); err != nil {
		return nil, cfg, err
	}
	key, secret, err := cfg.Credentials()
	if err != nil {
		return nil, cfg, err
	}
	c, err := s3.New(s3.Options{
		Endpoint: cfg.Endpoint,
		Region:   cfg.Region,
		Bucket:   cfg.Bucket,
		Prefix:   cfg.Prefix,
		KeyID:    key,
		Secret:   secret,
	})
	return c, cfg, err
}