// Package config loads smartrund's runtime configuration from environment
// variables (a single-user local app has no need for a config file/flags
// beyond this).
package config

import (
	"fmt"
	"os"
	"strconv"
	"time"
)

// Config holds everything smartrund needs to start.
type Config struct {
	// Addr is the HTTP listen address, e.g. ":8080".
	Addr string
	// DBPath is the SQLite database file path.
	DBPath string

	// GarminPythonPath is mcp-garmin's venv python executable.
	GarminPythonPath string
	// GarminServerPath is mcp-garmin's server.py.
	GarminServerPath string
	GarminEmail      string
	GarminPassword   string
	// GarminTokenStore, if set, overrides mcp-garmin's default ~/.garth
	// session cache location.
	GarminTokenStore string

	MaxHR                float64
	MinConfidence        float64
	BackfillHorizonDays  int
	IncrementalSyncEvery time.Duration
}

// Load reads configuration from environment variables, applying defaults
// for anything optional. Returns an error if a required variable is unset.
func Load() (Config, error) {
	cfg := Config{
		Addr:                 getEnvDefault("SMARTRUN_ADDR", ":8080"),
		DBPath:               getEnvDefault("SMARTRUN_DB_PATH", "smartrun.db"),
		GarminPythonPath:     os.Getenv("MCP_GARMIN_PYTHON"),
		GarminServerPath:     os.Getenv("MCP_GARMIN_SERVER"),
		GarminEmail:          os.Getenv("GARMIN_EMAIL"),
		GarminPassword:       os.Getenv("GARMIN_PASSWORD"),
		GarminTokenStore:     os.Getenv("GARMIN_TOKENSTORE"),
		MaxHR:                getEnvFloat("SMARTRUN_MAX_HR", 190),
		MinConfidence:        getEnvFloat("SMARTRUN_MIN_CONFIDENCE", 0.6),
		BackfillHorizonDays:  getEnvInt("SMARTRUN_BACKFILL_HORIZON_DAYS", 3*365),
		IncrementalSyncEvery: getEnvDuration("SMARTRUN_INCREMENTAL_SYNC_EVERY", 6*time.Hour),
	}

	if cfg.GarminPythonPath == "" {
		return cfg, fmt.Errorf("MCP_GARMIN_PYTHON is required (path to mcp-garmin's venv python)")
	}
	if cfg.GarminServerPath == "" {
		return cfg, fmt.Errorf("MCP_GARMIN_SERVER is required (path to mcp-garmin's server.py)")
	}
	if cfg.GarminEmail == "" || cfg.GarminPassword == "" {
		return cfg, fmt.Errorf("GARMIN_EMAIL and GARMIN_PASSWORD are required")
	}
	return cfg, nil
}

func getEnvDefault(key, def string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return def
}

func getEnvFloat(key string, def float64) float64 {
	if v := os.Getenv(key); v != "" {
		if f, err := strconv.ParseFloat(v, 64); err == nil {
			return f
		}
	}
	return def
}

func getEnvInt(key string, def int) int {
	if v := os.Getenv(key); v != "" {
		if n, err := strconv.Atoi(v); err == nil {
			return n
		}
	}
	return def
}

func getEnvDuration(key string, def time.Duration) time.Duration {
	if v := os.Getenv(key); v != "" {
		if d, err := time.ParseDuration(v); err == nil {
			return d
		}
	}
	return def
}