package config

import (
	"errors"
	"fmt"
	"os"

	"gopkg.in/yaml.v3"
)

type LoadOptions struct {
	Path     string
	Units    string
	Timezone string
	Output   string
}

func Load(opts LoadOptions) (Config, error) {
	cfg := Defaults()

	path := opts.Path
	if path == "" {
		path = DefaultPath
	}

	if err := mergeFile(&cfg, path); err != nil {
		if opts.Path != "" || !errors.Is(err, os.ErrNotExist) {
			return Config{}, err
		}
	}

	if opts.Units != "" {
		cfg.WeatherAPI.Units = opts.Units
	}
	if opts.Timezone != "" {
		cfg.WeatherAPI.Timezone = opts.Timezone
	}
	if opts.Output != "" {
		cfg.Reports.OutputDir = opts.Output
	}

	if err := Validate(cfg); err != nil {
		return Config{}, err
	}

	return cfg, nil
}

func LoadFile(path string) (Config, error) {
	return Load(LoadOptions{Path: path})
}

func mergeFile(cfg *Config, path string) error {
	data, err := os.ReadFile(path)
	if err != nil {
		return fmt.Errorf("read config %q: %w", path, err)
	}
	if err := yaml.Unmarshal(data, cfg); err != nil {
		return fmt.Errorf("parse config %q: %w", path, err)
	}
	if cfg.MissingSource.Sources == nil {
		cfg.MissingSource.Sources = map[string]MissingSourcePolicy{}
	}
	if cfg.Reports.Paths == nil {
		cfg.Reports.Paths = map[string]string{}
	}
	return nil
}