package config

import (
	"bytes"
	"errors"
	"fmt"
	"os"

	"gopkg.in/yaml.v3"
)

type LoadOptions struct {
	Path     string
	Units    string
	Timezone 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 err := normalizeReportModules(&cfg); err != nil {
		return Config{}, err
	}

	secrets, err := loadSecrets(cfg.Secrets)
	if err != nil {
		return Config{}, err
	}

	if err := Validate(cfg); err != nil {
		return Config{}, err
	}
	if err := applySecrets(secrets); 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 := rejectRetiredExecutionConfig(data); err != nil {
		return fmt.Errorf("parse config %q: %w", path, err)
	}
	decoder := yaml.NewDecoder(bytes.NewReader(data))
	decoder.KnownFields(true)
	if err := decoder.Decode(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 == nil {
		cfg.Reports = map[string]ReportConfig{}
	}
	return nil
}

func rejectRetiredExecutionConfig(data []byte) error {
	var document yaml.Node
	if err := yaml.Unmarshal(data, &document); err != nil {
		return err
	}
	if len(document.Content) == 0 || document.Content[0].Kind != yaml.MappingNode {
		return nil
	}
	root := document.Content[0]
	for i := 0; i+1 < len(root.Content); i += 2 {
		if root.Content[i].Value == "scriptorium" {
			return fmt.Errorf("scriptorium configuration is no longer supported; migrate to promptkit configuration")
		}
	}
	return nil
}