package eprel

import (
	"encoding/json"
	"fmt"
	"strconv"
	"strings"
)

var eprelIDKeys = []string{
	"eprel_id",
	"EPRELID",
	"eprelId",
	"EprelId",
	"eprelID",
}

// NormalizeID coerces XML/API values (string, number, {"#text": ...}) to a trimmed ID.
// Placeholder feed values like "0" / "0000" become empty so the EPREL step is not
// falsely "skipped" after a doomed fetch attempt.
func NormalizeID(v any) string {
	if v == nil {
		return ""
	}
	var s string
	switch t := v.(type) {
	case string:
		s = strings.TrimSpace(t)
	case json.Number:
		s = strings.TrimSpace(t.String())
		if i := strings.IndexByte(s, '.'); i >= 0 {
			s = s[:i]
		}
	case float64:
		if t != t { // NaN
			return ""
		}
		s = strconv.FormatInt(int64(t), 10)
	case float32:
		s = strconv.FormatInt(int64(t), 10)
	case int:
		s = strconv.Itoa(t)
	case int64:
		s = strconv.FormatInt(t, 10)
	case int32:
		s = strconv.FormatInt(int64(t), 10)
	case json.RawMessage:
		var decoded any
		if err := json.Unmarshal(t, &decoded); err != nil {
			return ""
		}
		return NormalizeID(decoded)
	case map[string]any:
		if text, ok := t["#text"]; ok {
			return NormalizeID(text)
		}
		if text, ok := t["text"]; ok {
			return NormalizeID(text)
		}
		return ""
	case []any:
		for _, item := range t {
			if id := NormalizeID(item); id != "" {
				return id
			}
		}
		return ""
	case []string:
		for _, item := range t {
			if id := NormalizeID(item); id != "" {
				return id
			}
		}
		return ""
	default:
		s = strings.TrimSpace(fmt.Sprint(t))
		if s == "" || s == "<nil>" {
			return ""
		}
	}
	if isPlaceholderEPRELID(s) {
		return ""
	}
	return s
}

func isPlaceholderEPRELID(id string) bool {
	id = strings.TrimSpace(id)
	if id == "" {
		return true
	}
	for _, r := range id {
		if r != '0' {
			return false
		}
	}
	return true
}

// IsValidID reports whether v normalizes to a non-empty EPREL registration id.
func IsValidID(v any) bool {
	return NormalizeID(v) != ""
}

// ExtractID finds an EPREL ID in mapped, raw, and/or attribute field maps
// (vendor feeds often use <EPRELID/> / eprel_id; specs parse may put it only in attrs).
func ExtractID(sources ...map[string]any) string {
	for _, src := range sources {
		if src == nil {
			continue
		}
		for _, key := range eprelIDKeys {
			if id := NormalizeID(src[key]); id != "" {
				return id
			}
		}
		for key, value := range src {
			compact := strings.ToLower(strings.ReplaceAll(key, "_", ""))
			if compact == "eprelid" {
				if id := NormalizeID(value); id != "" {
					return id
				}
			}
		}
	}
	return ""
}