package engine

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

	"github.com/spf13/viper"
)

type Config struct {
	DefaultFilter  string `mapstructure:"default_filter"`
	DefaultSort    string `mapstructure:"default_sort"`
	DefaultReport  string `mapstructure:"default_report"`
	ColorOutput    bool   `mapstructure:"color_output"`
	WeekStartDay   string `mapstructure:"week_start_day"`
	DefaultDueTime string `mapstructure:"default_due_time"`

	// Urgency coefficients
	UrgencyDue         float64 `mapstructure:"urgency_due_coefficient"`
	UrgencyPriorityH   float64 `mapstructure:"urgency_priority_h_coefficient"`
	UrgencyPriorityM   float64 `mapstructure:"urgency_priority_m_coefficient"`
	UrgencyPriorityD   float64 `mapstructure:"urgency_priority_d_coefficient"`
	UrgencyPriorityL   float64 `mapstructure:"urgency_priority_l_coefficient"`
	UrgencyActive      float64 `mapstructure:"urgency_active_coefficient"`
	UrgencyAge         float64 `mapstructure:"urgency_age_coefficient"`
	UrgencyAgeMax      int     `mapstructure:"urgency_age_max"`
	UrgencyTags        float64 `mapstructure:"urgency_tags_coefficient"`
	UrgencyProject     float64 `mapstructure:"urgency_project_coefficient"`
	UrgencyWaiting     float64 `mapstructure:"urgency_waiting_coefficient"`
	UrgencyUrgentTag   string  `mapstructure:"urgency_urgent_tag"`
	UrgencyUrgentCoeff float64 `mapstructure:"urgency_urgent_coefficient"`
	NextLimit          int     `mapstructure:"next_limit"`

	// Sync settings
	SyncEnabled      bool   `mapstructure:"sync_enabled"`
	SyncURL          string `mapstructure:"sync_url"`
	SyncAPIKey       string `mapstructure:"sync_api_key"`
	SyncClientID     string `mapstructure:"sync_client_id"`
	SyncStrategy     string `mapstructure:"sync_strategy"`
	SyncQueueOffline bool   `mapstructure:"sync_queue_offline"`
}

var globalConfig *Config

// Global variables for flag/programmatic overrides
var (
	configDirOverride string
	dataDirOverride   string
)

// SetConfigDirOverride sets the config directory override (typically from --config-dir flag)
func SetConfigDirOverride(dir string) {
	configDirOverride = dir
}

// SetDataDirOverride sets the data directory override (typically from --data-dir flag)
func SetDataDirOverride(dir string) {
	dataDirOverride = dir
}

// GetConfigDir returns the configuration directory path
// Resolution priority:
// 1. Flag override (via SetConfigDirOverride)
// 2. OPAL_CONFIG_DIR environment variable
// 3. XDG_CONFIG_HOME/opal
// 4. /etc/opal (with fallback to ~/.config/opal if not writable)
func GetConfigDir() (string, error) {
	// Priority 1: Flag override
	if configDirOverride != "" {
		return configDirOverride, nil
	}

	// Priority 2: Environment variable
	if dir := os.Getenv("OPAL_CONFIG_DIR"); dir != "" {
		return dir, nil
	}

	// Priority 3: XDG_CONFIG_HOME
	if xdgConfig := os.Getenv("XDG_CONFIG_HOME"); xdgConfig != "" {
		return filepath.Join(xdgConfig, "opal"), nil
	}

	// Priority 4: Try /etc/opal, fallback to ~/.config/opal if not writable
	etcOpal := "/etc/opal"
	if isWritable(etcOpal) {
		return etcOpal, nil
	}

	// Fallback to user config directory
	home, err := os.UserHomeDir()
	if err != nil {
		return "", fmt.Errorf("failed to get home directory: %w", err)
	}
	return filepath.Join(home, ".config", "opal"), nil
}

// GetDataDir returns the data directory path
// Resolution priority:
// 1. Flag override (via SetDataDirOverride)
// 2. OPAL_DATA_DIR environment variable
// 3. XDG_DATA_HOME/opal
// 4. /var/lib/opal (with fallback to ~/.local/share/opal if not writable)
func GetDataDir() (string, error) {
	// Priority 1: Flag override
	if dataDirOverride != "" {
		return dataDirOverride, nil
	}

	// Priority 2: Environment variable
	if dir := os.Getenv("OPAL_DATA_DIR"); dir != "" {
		return dir, nil
	}

	// Priority 3: XDG_DATA_HOME
	if xdgData := os.Getenv("XDG_DATA_HOME"); xdgData != "" {
		return filepath.Join(xdgData, "opal"), nil
	}

	// Priority 4: Try /var/lib/opal, fallback to ~/.local/share/opal if not writable
	varLibOpal := "/var/lib/opal"
	if isWritable(varLibOpal) {
		return varLibOpal, nil
	}

	// Fallback to user data directory
	home, err := os.UserHomeDir()
	if err != nil {
		return "", fmt.Errorf("failed to get home directory: %w", err)
	}
	return filepath.Join(home, ".local", "share", "opal"), nil
}

// isWritable checks if a directory exists and is writable, or if parent exists and is writable
func isWritable(path string) bool {
	// Check if path exists
	info, err := os.Stat(path)
	if err == nil {
		// Path exists, check if it's a directory and writable
		if !info.IsDir() {
			return false
		}
		// Test write permission by trying to create a temp file
		testFile := filepath.Join(path, ".write-test")
		f, err := os.Create(testFile)
		if err != nil {
			return false
		}
		f.Close()
		os.Remove(testFile)
		return true
	}

	// Path doesn't exist, check if parent is writable
	parent := filepath.Dir(path)
	parentInfo, err := os.Stat(parent)
	if err != nil {
		return false
	}
	if !parentInfo.IsDir() {
		return false
	}

	// Test if we can create in parent
	testFile := filepath.Join(parent, ".write-test")
	f, err := os.Create(testFile)
	if err != nil {
		return false
	}
	f.Close()
	os.Remove(testFile)
	return true
}

// GetDBPath returns the path to the SQLite database
// Resolution priority:
// 1. OPAL_DB_PATH environment variable
// 2. {data-dir}/opal.db
func GetDBPath() (string, error) {
	// Priority 1: OPAL_DB_PATH override
	if dbPath := os.Getenv("OPAL_DB_PATH"); dbPath != "" {
		return dbPath, nil
	}

	// Priority 2: Data directory + opal.db
	dataDir, err := GetDataDir()
	if err != nil {
		return "", err
	}
	return filepath.Join(dataDir, "opal.db"), nil
}

// GetConfigPath returns the path to the config file
func GetConfigPath() (string, error) {
	configDir, err := GetConfigDir()
	if err != nil {
		return "", err
	}
	return filepath.Join(configDir, "opal.yml"), nil
}

// GetSyncQueuePath returns the path to the sync queue file
func GetSyncQueuePath() (string, error) {
	dataDir, err := GetDataDir()
	if err != nil {
		return "", err
	}
	return filepath.Join(dataDir, "sync_queue.json"), nil
}

// GetSyncConflictLogPath returns the path to the sync conflict log
func GetSyncConflictLogPath() (string, error) {
	dataDir, err := GetDataDir()
	if err != nil {
		return "", err
	}
	return filepath.Join(dataDir, "sync_conflicts.log"), nil
}

// LoadConfig loads the configuration from file or creates default
func LoadConfig() (*Config, error) {
	if globalConfig != nil {
		return globalConfig, nil
	}

	configDir, err := GetConfigDir()
	if err != nil {
		return nil, err
	}

	// Ensure config directory exists
	if err := os.MkdirAll(configDir, 0755); err != nil {
		return nil, fmt.Errorf("failed to create config directory: %w", err)
	}

	configPath, err := GetConfigPath()
	if err != nil {
		return nil, err
	}

	v := viper.New()
	v.SetConfigFile(configPath)
	v.SetConfigType("yaml")

	// Set defaults
	v.SetDefault("default_filter", "status:pending")
	v.SetDefault("default_sort", "due,priority")
	v.SetDefault("default_report", "list")
	v.SetDefault("color_output", true)
	v.SetDefault("week_start_day", "monday")
	v.SetDefault("default_due_time", "")

	// Urgency defaults (adjusted for Opal's simpler model)
	v.SetDefault("urgency_due_coefficient", 12.0)
	v.SetDefault("urgency_priority_h_coefficient", 6.0)
	v.SetDefault("urgency_priority_m_coefficient", 3.9)
	v.SetDefault("urgency_priority_d_coefficient", 1.8)
	v.SetDefault("urgency_priority_l_coefficient", 0.0)
	v.SetDefault("urgency_active_coefficient", 4.0)
	v.SetDefault("urgency_age_coefficient", 2.0)
	v.SetDefault("urgency_age_max", 365)
	v.SetDefault("urgency_tags_coefficient", 1.0)
	v.SetDefault("urgency_project_coefficient", 1.0)
	v.SetDefault("urgency_waiting_coefficient", -3.0)
	v.SetDefault("urgency_urgent_tag", "next")
	v.SetDefault("urgency_urgent_coefficient", 15.0)
	v.SetDefault("next_limit", 5)

	// Sync defaults
	v.SetDefault("sync_enabled", false)
	v.SetDefault("sync_url", "")
	v.SetDefault("sync_api_key", "")
	v.SetDefault("sync_client_id", "")
	v.SetDefault("sync_strategy", "last-write-wins")
	v.SetDefault("sync_queue_offline", true)

	// Try to read existing config
	err = v.ReadInConfig()
	if err != nil {
		// Config doesn't exist, create it with defaults
		// Write config with defaults (ignoring the error type check for now)
		if err := v.WriteConfigAs(configPath); err != nil {
			return nil, fmt.Errorf("failed to create config file: %w", err)
		}
		// Try reading again
		if err := v.ReadInConfig(); err != nil {
			return nil, fmt.Errorf("failed to read newly created config: %w", err)
		}
	}

	cfg := &Config{}
	if err := v.Unmarshal(cfg); err != nil {
		return nil, fmt.Errorf("failed to unmarshal config: %w", err)
	}

	globalConfig = cfg
	return cfg, nil
}

// SaveConfig saves the configuration to file
func SaveConfig(cfg *Config) error {
	configPath, err := GetConfigPath()
	if err != nil {
		return err
	}

	v := viper.New()
	v.SetConfigFile(configPath)
	v.SetConfigType("yaml")

	v.Set("default_filter", cfg.DefaultFilter)
	v.Set("default_sort", cfg.DefaultSort)
	v.Set("default_report", cfg.DefaultReport)
	v.Set("color_output", cfg.ColorOutput)
	v.Set("week_start_day", cfg.WeekStartDay)
	v.Set("default_due_time", cfg.DefaultDueTime)

	// Urgency settings
	v.Set("urgency_due_coefficient", cfg.UrgencyDue)
	v.Set("urgency_priority_h_coefficient", cfg.UrgencyPriorityH)
	v.Set("urgency_priority_m_coefficient", cfg.UrgencyPriorityM)
	v.Set("urgency_priority_d_coefficient", cfg.UrgencyPriorityD)
	v.Set("urgency_priority_l_coefficient", cfg.UrgencyPriorityL)
	v.Set("urgency_active_coefficient", cfg.UrgencyActive)
	v.Set("urgency_age_coefficient", cfg.UrgencyAge)
	v.Set("urgency_age_max", cfg.UrgencyAgeMax)
	v.Set("urgency_tags_coefficient", cfg.UrgencyTags)
	v.Set("urgency_project_coefficient", cfg.UrgencyProject)
	v.Set("urgency_waiting_coefficient", cfg.UrgencyWaiting)
	v.Set("urgency_urgent_tag", cfg.UrgencyUrgentTag)
	v.Set("urgency_urgent_coefficient", cfg.UrgencyUrgentCoeff)
	v.Set("next_limit", cfg.NextLimit)

	// Sync settings
	v.Set("sync_enabled", cfg.SyncEnabled)
	v.Set("sync_url", cfg.SyncURL)
	v.Set("sync_api_key", cfg.SyncAPIKey)
	v.Set("sync_client_id", cfg.SyncClientID)
	v.Set("sync_strategy", cfg.SyncStrategy)
	v.Set("sync_queue_offline", cfg.SyncQueueOffline)

	return v.WriteConfig()
}

// GetConfig returns the loaded config or loads it if not already loaded
func GetConfig() (*Config, error) {
	if globalConfig != nil {
		return globalConfig, nil
	}
	return LoadConfig()
}

// GetWeekStart returns the configured week start day
func (c *Config) GetWeekStart() time.Weekday {
	if strings.ToLower(c.WeekStartDay) == "sunday" {
		return time.Sunday
	}
	return time.Monday // default
}

// GetDefaultDueTime returns the configured default due time (HH:MM format or empty)
func (c *Config) GetDefaultDueTime() string {
	return c.DefaultDueTime
}