package config

import (
	"fmt"
	"net/url"
	"strconv"
	"strings"

	"gitea.maximumdirect.net/eric/weatherreporter/internal/timeutil"
)

func Validate(cfg Config) error {
	if cfg.WeatherAPI.BaseURL != "" {
		parsed, err := url.Parse(cfg.WeatherAPI.BaseURL)
		if err != nil || parsed.Scheme == "" || parsed.Host == "" {
			return fmt.Errorf("weather_api.base_url must be an absolute URL")
		}
	}
	if cfg.WeatherAPI.Timeout <= 0 {
		return fmt.Errorf("weather_api.timeout must be greater than zero")
	}
	if cfg.WeatherAPI.Precision < 0 {
		return fmt.Errorf("weather_api.precision must be zero or greater")
	}
	if cfg.WeatherAPI.Units == "" {
		return fmt.Errorf("weather_api.units is required")
	}
	if cfg.WeatherAPI.Timezone == "" {
		return fmt.Errorf("weather_api.timezone is required")
	}
	if _, err := timeutil.LoadLocation(cfg.WeatherAPI.Timezone); err != nil {
		return fmt.Errorf("weather_api.timezone %q is invalid: %w", cfg.WeatherAPI.Timezone, err)
	}
	if cfg.WeatherAPI.Format == "" {
		return fmt.Errorf("weather_api.format is required")
	}
	if cfg.WeatherAPI.Format != "json" {
		return fmt.Errorf("weather_api.format must be json")
	}

	if err := validatePolicy("missing_source.default", cfg.MissingSource.Default); err != nil {
		return err
	}
	for source, policy := range cfg.MissingSource.Sources {
		if strings.TrimSpace(source) == "" {
			return fmt.Errorf("missing_source.sources contains an empty source name")
		}
		if err := validatePolicy("missing_source.sources."+source, policy); err != nil {
			return err
		}
	}

	if cfg.Scriptorium.Binary == "" {
		return fmt.Errorf("scriptorium.binary is required")
	}
	if cfg.Scriptorium.Timeout <= 0 {
		return fmt.Errorf("scriptorium.timeout must be greater than zero")
	}
	if cfg.Workspace.Root == "" {
		return fmt.Errorf("workspace.root is required")
	}
	if cfg.Reports.OutputDir == "" {
		return fmt.Errorf("reports.output_dir is required")
	}
	if len(cfg.Dayparts) == 0 {
		return fmt.Errorf("dayparts must contain at least one entry")
	}
	for i, daypart := range cfg.Dayparts {
		if strings.TrimSpace(daypart.Name) == "" {
			return fmt.Errorf("dayparts[%d].name is required", i)
		}
		if err := validateClockTime(daypart.Start); err != nil {
			return fmt.Errorf("dayparts[%d].start is invalid: %w", i, err)
		}
		if err := validateClockTime(daypart.End); err != nil {
			return fmt.Errorf("dayparts[%d].end is invalid: %w", i, err)
		}
	}
	return nil
}

func validatePolicy(name string, policy MissingSourcePolicy) error {
	switch policy {
	case MissingSourceError, MissingSourceWarn, MissingSourceNone:
		return nil
	default:
		return fmt.Errorf("%s must be one of error, warn, or none", name)
	}
}

func validateClockTime(value string) error {
	parts := strings.Split(value, ":")
	if len(parts) != 2 {
		return fmt.Errorf("expected HH:MM")
	}
	hour, err := strconv.Atoi(parts[0])
	if err != nil {
		return fmt.Errorf("invalid hour")
	}
	minute, err := strconv.Atoi(parts[1])
	if err != nil {
		return fmt.Errorf("invalid minute")
	}
	if hour < 0 || hour > 24 {
		return fmt.Errorf("hour must be between 00 and 24")
	}
	if minute < 0 || minute > 59 {
		return fmt.Errorf("minute must be between 00 and 59")
	}
	if hour == 24 && minute != 0 {
		return fmt.Errorf("24 is only valid as 24:00")
	}
	return nil
}