package compass

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"github.com/knadh/koanf/parsers/yaml"
	"github.com/knadh/koanf/v2"
)

// Config is a YAML configuration tree with dot-path access.
type Config struct {
	k *koanf.Koanf
}

// Load reads config/<section>.yaml files from dir. Each filename stem becomes
// the top-level section, so config/app.yaml key name is app.name.
func Load(dir string) (*Config, error) {
	k := koanf.New(".")
	entries, err := os.ReadDir(dir)
	if err != nil {
		return nil, fmt.Errorf("compass: read config dir %s: %w", dir, err)
	}
	parser := yaml.Parser()
	for _, entry := range entries {
		if entry.IsDir() {
			continue
		}
		name := entry.Name()
		section, ok := sectionName(name)
		if !ok {
			continue
		}
		path := filepath.Join(dir, name)
		raw, err := os.ReadFile(path)
		if err != nil {
			return nil, fmt.Errorf("compass: read %s: %w", path, err)
		}
		parsed, err := parser.Unmarshal(raw)
		if err != nil {
			return nil, fmt.Errorf("compass: parse %s: %w", path, err)
		}
		if parsed == nil {
			parsed = map[string]any{}
		}
		if err := k.Set(section, parsed); err != nil {
			return nil, fmt.Errorf("compass: set section %s: %w", section, err)
		}
	}
	return &Config{k: k}, nil
}

// String returns the string value at path, or "" if unset.
func (c *Config) String(path string) string {
	if c == nil || c.k == nil {
		return ""
	}
	return c.k.String(path)
}

func sectionName(filename string) (string, bool) {
	switch {
	case strings.HasSuffix(filename, ".yaml"):
		return strings.TrimSuffix(filename, ".yaml"), true
	case strings.HasSuffix(filename, ".yml"):
		return strings.TrimSuffix(filename, ".yml"), true
	default:
		return "", false
	}
}