package config

import (
	"fmt"
	"os"
	"time"

	"gopkg.in/yaml.v3"
)

// Config is the top-level EMS configuration.
type Config struct {
	Prometheus PrometheusConfig  `yaml:"prometheus"`
	Shelly     ShellyConfig      `yaml:"shelly"`
	Viessmann  ViessmannConfig   `yaml:"viessmann"`
	SOC        SOCThresholds     `yaml:"soc_thresholds"`
	Hysteresis HysteresisConfig  `yaml:"hysteresis"`
	Thresholds PowerThresholds   `yaml:"thresholds"`
	Consumers  ConsumersConfig   `yaml:"consumers"`
	Strategic  StrategicConfig   `yaml:"strategic"`
	Season     SeasonConfig      `yaml:"season"`
	Forecast   ForecastConfig    `yaml:"forecast"`
	EMS        EMSConfig         `yaml:"ems"`
}

// PrometheusConfig holds Prometheus connection settings.
type PrometheusConfig struct {
	URL     string            `yaml:"url"`
	Metrics map[string]string `yaml:"metrics"`
}

// ShellyConfig holds all Shelly actuator addresses.
type ShellyConfig struct {
	SGReady  ShellyDevice `yaml:"sg_ready"`
	WallboxA ShellyDevice `yaml:"wallbox_a"`
	WallboxB ShellyDevice `yaml:"wallbox_b"`
}

// ShellyDevice represents a single Shelly device.
type ShellyDevice struct {
	IP       string `yaml:"ip"`
	Gen      int    `yaml:"gen"`
	PowerW   int    `yaml:"power_w"`
	Password string `yaml:"password"` // optional; Gen2 uses HTTP Digest auth
}

// ViessmannConfig holds Viessmann API credentials (write access for WW temp).
type ViessmannConfig struct {
	TokenFile      string `yaml:"token_file"`
	ClientID       string `yaml:"client_id"`
	InstallationID string `yaml:"installation_id"`
	GatewaySerial  string `yaml:"gateway_serial"`
	DeviceID       string `yaml:"device_id"`
}

// SOCThresholds defines the battery SOC levels that gate consumers.
type SOCThresholds struct {
	BlockAll     float64 `yaml:"block_all"`
	SGReadyOnly  float64 `yaml:"sg_ready_only"`
	PlusWallboxA float64 `yaml:"plus_wallbox_a"`
	AllConsumers float64 `yaml:"all_consumers"`
}

// HysteresisConfig defines timing parameters for switching decisions.
type HysteresisConfig struct {
	ExportOnDuration  string `yaml:"export_on_duration"`
	ImportOffDuration string `yaml:"import_off_duration"`
	MinRuntimeWallbox string `yaml:"min_runtime_wallbox"`
	MinRuntimeSGReady string `yaml:"min_runtime_sg_ready"`
}

func (h *HysteresisConfig) ExportOnDurationParsed() time.Duration {
	d, _ := time.ParseDuration(h.ExportOnDuration)
	return d
}

func (h *HysteresisConfig) ImportOffDurationParsed() time.Duration {
	d, _ := time.ParseDuration(h.ImportOffDuration)
	return d
}

func (h *HysteresisConfig) MinRuntimeWallboxParsed() time.Duration {
	d, _ := time.ParseDuration(h.MinRuntimeWallbox)
	return d
}

func (h *HysteresisConfig) MinRuntimeSGReadyParsed() time.Duration {
	d, _ := time.ParseDuration(h.MinRuntimeSGReady)
	return d
}

// PowerThresholds defines the grid power levels that trigger switching.
// Export thresholds are negative (grid exports = negative grid power).
type PowerThresholds struct {
	SGReadyExportW       float64 `yaml:"sg_ready_export_w"`
	WWExportW            float64 `yaml:"ww_export_w"`
	WallboxAExportW      float64 `yaml:"wallbox_a_export_w"`
	WallboxAPhaseExportW float64 `yaml:"wallbox_a_phase_export_w"` // per-phase export for single-phase WallboxA
	WallboxBExportW      float64 `yaml:"wallbox_b_export_w"`
	ImportOffW           float64 `yaml:"import_off_w"`
}

// ConsumersConfig holds per-consumer behavior thresholds.
type ConsumersConfig struct {
	CompressorIdleW  int `yaml:"compressor_idle_w"`  // below this = heat pump compressor idle (W)
	WallboxMinChargeW int `yaml:"wallbox_min_charge_w"` // below this = car not charging (W)
	IdleCycles       int `yaml:"idle_cycles"`          // consecutive idle cycles before early release
}

// StrategicConfig holds PV forecast based strategic settings.
type StrategicConfig struct {
	ForecastHighKWh float64 `yaml:"forecast_high_kwh"`
	ForecastMidKWh  float64 `yaml:"forecast_mid_kwh"`
	WWBoostHighC    float64 `yaml:"ww_boost_high_c"`
	WWBoostMidC     float64 `yaml:"ww_boost_mid_c"`
	WWBaseC         float64 `yaml:"ww_base_c"`       // normal WW setpoint (°C)
	WWWindowStart   string  `yaml:"ww_window_start"` // e.g. "12:30"
	WWWindowEnd     string  `yaml:"ww_window_end"`   // e.g. "18:00"
	ScheduleOn      string  `yaml:"schedule_on"`
	ScheduleOff     string  `yaml:"schedule_off"`
}

// SeasonConfig defines the heating season by month range and ambient temperature.
type SeasonConfig struct {
	HeatingStartMonth  int     `yaml:"heating_start_month"`
	HeatingEndMonth    int     `yaml:"heating_end_month"`
	HeatingMinAmbientC float64 `yaml:"heating_min_ambient_c"` // above this: non-heating regardless of month (0 = disabled)
}

// ForecastConfig holds forecast.solar API parameters.
type ForecastConfig struct {
	Enabled          bool    `yaml:"enabled"`
	Lat              float64 `yaml:"lat"`
	Lon              float64 `yaml:"lon"`
	Declination      int     `yaml:"declination"`        // panel tilt in degrees
	Azimuth          int     `yaml:"azimuth"`            // degrees from south (south=0, west=90)
	KWp              float64 `yaml:"kwp"`                // installed peak power
	FetchInterval    string  `yaml:"fetch_interval"`     // how often to re-fetch during the day
	FetchWindowStart string  `yaml:"fetch_window_start"` // e.g. "07:00"
	FetchWindowEnd   string  `yaml:"fetch_window_end"`   // e.g. "19:00"
	BaseLoadW        float64 `yaml:"base_load_w"`        // typical house consumption for surplus estimate (W)
	MinSurplusW      float64 `yaml:"min_surplus_w"`      // min export needed to trigger wallbox charging (W)
}

func (f *ForecastConfig) FetchIntervalParsed() time.Duration {
	d, err := time.ParseDuration(f.FetchInterval)
	if err != nil || d <= 0 {
		return 24 * time.Hour // safe default: once per day
	}
	return d
}

// EMSConfig holds operational settings for the EMS daemon.
type EMSConfig struct {
	PollInterval       string  `yaml:"poll_interval"`
	ListenAddr         string  `yaml:"listen_addr"`
	LogLevel           string  `yaml:"log_level"`
	StateFile          string  `yaml:"state_file"`
	RecoveryTimeout    string  `yaml:"recovery_timeout"`
	OverrideTimeout    string  `yaml:"override_timeout"`
	OverrideMaxImportW float64 `yaml:"override_max_import_w"` // cancel override if grid import exceeds this (0 = disabled)
	MonitorOnlyFile    string  `yaml:"monitor_only_file"`     // flag file path: presence = monitor-only mode active
}

func (e *EMSConfig) PollIntervalParsed() time.Duration {
	d, _ := time.ParseDuration(e.PollInterval)
	return d
}

func (e *EMSConfig) RecoveryTimeoutParsed() time.Duration {
	d, err := time.ParseDuration(e.RecoveryTimeout)
	if err != nil {
		return time.Hour // safe default
	}
	return d
}

func (e *EMSConfig) OverrideTimeoutParsed() time.Duration {
	d, err := time.ParseDuration(e.OverrideTimeout)
	if err != nil {
		return time.Hour // safe default
	}
	return d
}

// Load reads and parses the YAML config file at the given path.
func Load(path string) (*Config, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("reading config file: %w", err)
	}

	var cfg Config
	if err := yaml.Unmarshal(data, &cfg); err != nil {
		return nil, fmt.Errorf("parsing config file: %w", err)
	}

	if err := cfg.validate(); err != nil {
		return nil, fmt.Errorf("invalid config: %w", err)
	}

	return &cfg, nil
}

func (c *Config) validate() error {
	if c.Prometheus.URL == "" {
		return fmt.Errorf("prometheus.url is required")
	}
	if c.EMS.PollInterval == "" {
		return fmt.Errorf("ems.poll_interval is required")
	}
	if _, err := time.ParseDuration(c.EMS.PollInterval); err != nil {
		return fmt.Errorf("ems.poll_interval %q: %w", c.EMS.PollInterval, err)
	}
	if c.EMS.ListenAddr == "" {
		return fmt.Errorf("ems.listen_addr is required")
	}
	return nil
}