package internal

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"github.com/adrg/xdg"
	"github.com/spf13/viper"

	"github.com/ivuorinen/gh-action-readme/appconstants"
)

// initializeViperInstance creates and configures a new viper instance with standard settings.
// This includes XDG-compliant configuration paths, environment variable support,
// and standard search paths for configuration files.
func initializeViperInstance() (*viper.Viper, error) {
	v := viper.New()

	// Set configuration file name and type
	v.SetConfigName(appconstants.ConfigFileName)
	v.SetConfigType(appconstants.OutputFormatYAML)

	// Add XDG-compliant configuration directory
	configDir, err := xdg.ConfigFile(appconstants.PathXDGConfig)
	if err != nil {
		return nil, fmt.Errorf(appconstants.ErrFailedToGetXDGConfigDir, err)
	}
	v.AddConfigPath(filepath.Dir(configDir))

	// Add additional search paths
	v.AddConfigPath(".") // current directory

	// Expand home directory for fallback config path
	if home, err := os.UserHomeDir(); err == nil {
		v.AddConfigPath(filepath.Join(home, ".config", appconstants.AppName)) // fallback
	}

	v.AddConfigPath(appconstants.PathEtcConfig) // system-wide

	// Set environment variable prefix
	v.SetEnvPrefix(appconstants.EnvPrefix)
	v.SetEnvKeyReplacer(strings.NewReplacer("-", "_", ".", "_"))
	v.AutomaticEnv()

	return v, nil
}

// setConfigDefaults sets all default configuration values in the viper instance.
// This ensures consistent default values across all configuration loading scenarios.
func setConfigDefaults(v *viper.Viper, defaults *AppConfig) {
	v.SetDefault(appconstants.ConfigKeyOrganization, defaults.Organization)
	v.SetDefault(appconstants.ConfigKeyRepository, defaults.Repository)
	v.SetDefault(appconstants.ConfigKeyVersion, defaults.Version)
	v.SetDefault(appconstants.ConfigKeyTheme, defaults.Theme)
	v.SetDefault(appconstants.ConfigKeyOutputFormat, defaults.OutputFormat)
	v.SetDefault(appconstants.ConfigKeyOutputDir, defaults.OutputDir)
	v.SetDefault(appconstants.ConfigKeyTemplate, defaults.Template)
	v.SetDefault(appconstants.ConfigKeyHeader, defaults.Header)
	v.SetDefault(appconstants.ConfigKeyFooter, defaults.Footer)
	v.SetDefault(appconstants.ConfigKeySchema, defaults.Schema)
	v.SetDefault(appconstants.ConfigKeyAnalyzeDependencies, defaults.AnalyzeDependencies)
	v.SetDefault(appconstants.ConfigKeyShowSecurityInfo, defaults.ShowSecurityInfo)
	v.SetDefault(appconstants.ConfigKeyVerbose, defaults.Verbose)
	v.SetDefault(appconstants.ConfigKeyQuiet, defaults.Quiet)
	v.SetDefault(appconstants.ConfigKeyIgnoredDirectories, defaults.IgnoredDirectories)
	v.SetDefault(appconstants.ConfigKeyDefaultsName, defaults.Defaults.Name)
	v.SetDefault(appconstants.ConfigKeyDefaultsDescription, defaults.Defaults.Description)
	v.SetDefault(appconstants.ConfigKeyDefaultsBrandingIcon, defaults.Defaults.Branding.Icon)
	v.SetDefault(appconstants.ConfigKeyDefaultsBrandingColor, defaults.Defaults.Branding.Color)
}

// loadConfigFromViper loads an AppConfig from a specified YAML config file using viper.
func loadConfigFromViper(configPath string) (*AppConfig, error) {
	v := viper.New()
	v.SetConfigFile(configPath)
	v.SetConfigType(appconstants.OutputFormatYAML)

	if err := v.ReadInConfig(); err != nil {
		return nil, fmt.Errorf("failed to read config %s: %w", configPath, err)
	}

	var config AppConfig
	if err := v.Unmarshal(&config); err != nil {
		return nil, fmt.Errorf(appconstants.ErrFailedToUnmarshalConfig, err)
	}

	return &config, nil
}

// loadAndUnmarshalConfig initializes viper with defaults, reads config file,
// and unmarshals into AppConfig with proper error handling.
// Returns *AppConfig with resolved template paths.
func loadAndUnmarshalConfig(configFile string, v *viper.Viper) (*AppConfig, error) {
	// Set defaults
	defaults := DefaultAppConfig()
	setConfigDefaults(v, defaults)

	// Use specific config file if provided
	if configFile != "" {
		v.SetConfigFile(configFile)
	}

	// Read configuration
	if err := v.ReadInConfig(); err != nil {
		if _, ok := err.(viper.ConfigFileNotFoundError); !ok {
			return nil, fmt.Errorf(appconstants.ErrFailedToReadConfigFile, err)
		}
		// Config file not found is not an error - we'll use defaults and env vars
	}

	// Unmarshal configuration into struct
	var config AppConfig
	if err := v.Unmarshal(&config); err != nil {
		return nil, fmt.Errorf(appconstants.ErrFailedToUnmarshalConfig, err)
	}

	// Resolve template paths relative to binary if they're not absolute
	resolveAllTemplatePaths(&config)

	return &config, nil
}