package eprel

import (
	"fmt"
	"strings"
)

// ExtractFromAttrs builds the nested EPREL object used by V1 process items and
// the dashboard product API (id / label / pdf / energy_class / energy_scale).
// Returns nil when no usable EPREL fields are present.
//
// Nested attrs["eprel"] may use flat export aliases (eprel_id, eprel_label, …);
// those are normalized onto the public keys. Flat eprel_* keys fill any gaps.
func ExtractFromAttrs(attrs map[string]any) any {
	if attrs == nil {
		return nil
	}
	out := map[string]any{}
	if e, ok := attrs["eprel"]; ok && e != nil {
		switch t := e.(type) {
		case map[string]any:
			for k, v := range t {
				if s := attrString(v); s == "" {
					continue
				} else {
					out[strings.TrimSpace(k)] = s
				}
			}
		default:
			if s := attrString(e); s != "" {
				return map[string]any{"id": s}
			}
			return nil
		}
	}
	put := func(dstKey string, keys ...string) {
		if attrString(out[dstKey]) != "" {
			return
		}
		for _, k := range keys {
			if s := attrString(attrs[k]); s != "" {
				out[dstKey] = s
				return
			}
			// Also accept aliases already copied from a nested object.
			if s := attrString(out[k]); s != "" {
				out[dstKey] = s
				return
			}
		}
	}
	put("id", "eprel_id", "EPRELID", "eprelId")
	put("label", "eprel_label", "eprel_label_url")
	put("pdf", "eprel_pdf", "eprel_pdf_url")
	put("energy_class", "eprel_energy_class", "energyClass")
	put("energy_scale", "eprel_energy_scale", "energyClassRange", "energyScale")
	return NormalizeShape(out)
}

// NormalizeShape keeps only the public EPREL keys with non-empty string values.
// Alias keys (eprel_id, …) are folded onto id/label/pdf/energy_class/energy_scale.
func NormalizeShape(v any) any {
	if v == nil {
		return nil
	}
	m, ok := v.(map[string]any)
	if !ok {
		return nil
	}
	if len(m) == 0 {
		return nil
	}
	out := map[string]any{}
	for k, val := range m {
		if s := attrString(val); s != "" {
			out[strings.TrimSpace(k)] = s
		}
	}
	fold := func(dst string, aliases ...string) {
		if attrString(out[dst]) != "" {
			for _, a := range aliases {
				delete(out, a)
			}
			return
		}
		for _, a := range aliases {
			if s := attrString(out[a]); s != "" {
				out[dst] = s
				break
			}
		}
		for _, a := range aliases {
			delete(out, a)
		}
	}
	fold("id", "eprel_id", "EPRELID", "eprelId")
	fold("label", "eprel_label", "eprel_label_url")
	fold("pdf", "eprel_pdf", "eprel_pdf_url")
	fold("energy_class", "eprel_energy_class", "energyClass")
	fold("energy_scale", "eprel_energy_scale", "energyClassRange", "energyScale")

	canonical := map[string]any{}
	for _, k := range []string{"id", "label", "pdf", "energy_class", "energy_scale"} {
		if s := attrString(out[k]); s != "" {
			canonical[k] = s
		}
	}
	if len(canonical) == 0 {
		return nil
	}
	return canonical
}

func attrString(v any) string {
	if v == nil {
		return ""
	}
	switch t := v.(type) {
	case string:
		return strings.TrimSpace(t)
	case float64:
		// JSON numbers for numeric eprel ids.
		if t == float64(int64(t)) {
			return strings.TrimSpace(fmt.Sprintf("%.0f", t))
		}
		return strings.TrimSpace(fmt.Sprint(t))
	case int:
		return fmt.Sprintf("%d", t)
	case int64:
		return fmt.Sprintf("%d", t)
	case map[string]any:
		for _, k := range []string{"value", "#text", "text", "id"} {
			if s := attrString(t[k]); s != "" {
				return s
			}
		}
		return ""
	default:
		s := strings.TrimSpace(fmt.Sprint(v))
		if s == "" || s == "<nil>" {
			return ""
		}
		return s
	}
}