package config

import (
	"fmt"
	"os"
	"strings"
)

// Config is the top-level configuration.
type Config struct {
	Global   GlobalConfig   `mapstructure:"global"`
	Projects []ProjectConfig `mapstructure:"projects"`
	Remote   *RemoteConfig  `mapstructure:"remote"`
}

// GlobalConfig holds global settings.
type GlobalConfig struct {
	BackupDir string `mapstructure:"backup_dir"`
	TempDir   string `mapstructure:"temp_dir"`
}

// ProjectConfig defines one Docker Compose project to back up.
type ProjectConfig struct {
	Name        string          `mapstructure:"name"`
	Path        string          `mapstructure:"path"`
	ComposeFile string          `mapstructure:"compose_file"`
	Cron        string          `mapstructure:"cron"`
	Exclude     []string        `mapstructure:"exclude"`
	Retention   RetentionConfig `mapstructure:"retention"`
}

// RetentionConfig controls backup cleanup policy.
type RetentionConfig struct {
	Count int `mapstructure:"count"`
	Days  int `mapstructure:"days"`
}

// RemoteConfig holds optional remote upload targets.
type RemoteConfig struct {
	S3     *S3Config     `mapstructure:"s3"`
	WebDAV *WebDAVConfig `mapstructure:"webdav"`
}

// S3Config is the S3-compatible storage backend config.
type S3Config struct {
	Endpoint   string `mapstructure:"endpoint"`
	Bucket     string `mapstructure:"bucket"`
	AccessKey  string `mapstructure:"access_key"`
	SecretKey  string `mapstructure:"secret_key"`
	Region     string `mapstructure:"region"`
	PathPrefix string `mapstructure:"path_prefix"`
}

// WebDAVConfig is the WebDAV storage backend config.
type WebDAVConfig struct {
	URL      string `mapstructure:"url"`
	Username string `mapstructure:"username"`
	Password string `mapstructure:"password"`
}

// DefaultRetentionCount is used when no retention count is specified.
const DefaultRetentionCount = 7

// Validate checks the configuration and fills in defaults.
func (c *Config) Validate() error {
	if c.Global.BackupDir == "" {
		return fmt.Errorf("global.backup_dir is required")
	}
	if c.Global.TempDir == "" {
		c.Global.TempDir = os.TempDir()
	}

	if len(c.Projects) == 0 {
		return fmt.Errorf("at least one project must be configured")
	}

	for i := range c.Projects {
		p := &c.Projects[i]
		if p.Name == "" {
			return fmt.Errorf("projects[%d]: name is required", i)
		}
		if p.Path == "" {
			return fmt.Errorf("projects[%d] (%s): path is required", i, p.Name)
		}
		if p.ComposeFile == "" {
			p.ComposeFile = "docker-compose.yml"
		}
		if p.Retention.Count <= 0 {
			p.Retention.Count = DefaultRetentionCount
		}
	}

	// Expand environment variable placeholders in remote configs and validate required fields.
	if c.Remote != nil {
		if c.Remote.S3 != nil {
			c.Remote.S3.AccessKey = expandEnv(c.Remote.S3.AccessKey)
			c.Remote.S3.SecretKey = expandEnv(c.Remote.S3.SecretKey)
			if strings.TrimSpace(c.Remote.S3.Bucket) == "" {
				return fmt.Errorf("remote.s3.bucket is required")
			}
			if strings.TrimSpace(c.Remote.S3.Region) == "" {
				return fmt.Errorf("remote.s3.region is required")
			}
			if strings.TrimSpace(c.Remote.S3.AccessKey) == "" {
				return fmt.Errorf("remote.s3.access_key is required")
			}
			if strings.TrimSpace(c.Remote.S3.SecretKey) == "" {
				return fmt.Errorf("remote.s3.secret_key is required")
			}
		}
		if c.Remote.WebDAV != nil {
			c.Remote.WebDAV.Username = expandEnv(c.Remote.WebDAV.Username)
			c.Remote.WebDAV.Password = expandEnv(c.Remote.WebDAV.Password)
			if strings.TrimSpace(c.Remote.WebDAV.URL) == "" {
				return fmt.Errorf("remote.webdav.url is required")
			}
		}
	}

	return nil
}

// expandEnv replaces ${VAR} or $VAR placeholders with environment values.
func expandEnv(s string) string {
	return os.Expand(s, func(key string) string {
		return os.Getenv(key)
	})
}

// HasRemote returns true if at least one remote backend is configured.
func (c *Config) HasRemote() bool {
	return c.Remote != nil && (c.Remote.S3 != nil || c.Remote.WebDAV != nil)
}

// HasCron returns true if at least one project has a cron expression.
func (c *Config) HasCron() bool {
	for _, p := range c.Projects {
		if strings.TrimSpace(p.Cron) != "" {
			return true
		}
	}
	return false
}