package eprel

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"

	"github.com/descrybe/descrybe-v2/apps/api/internal/security"
)

const (
	defaultBaseURL       = "https://eprel.ec.europa.eu/api"
	defaultTimeout       = 10 * time.Second
	defaultFicheLanguage = "EN"
	maxBodyBytes         = 2 << 20
)

var allowedFicheLanguages = map[string]struct{}{
	"EN": {}, "DE": {}, "FR": {}, "NL": {}, "ES": {}, "IT": {},
}

func isAllowedFicheLanguage(code string) bool {
	_, ok := allowedFicheLanguages[code]
	return ok
}

// Data is the public energy-label payload attached to processed products.
type Data struct {
	ID          string `json:"id"`
	Label       string `json:"label"`
	PDF         string `json:"pdf,omitempty"`
	EnergyClass string `json:"energy_class,omitempty"`
	EnergyScale string `json:"energy_scale,omitempty"`
}

// Fetcher is the test seam for EPREL HTTP calls.
type Fetcher interface {
	Enabled() bool
	Fetch(ctx context.Context, eprelID string) (*Data, error)
}

// Client calls the public EPREL product API with timeouts and bounded bodies.
type Client struct {
	BaseURL       string
	FicheLanguage string
	APIKey        string // optional; never logged
	HTTP          *http.Client
	enabled       bool
}

// Options configures a Client.
type Options struct {
	Enabled       bool
	BaseURL       string
	Timeout       time.Duration
	FicheLanguage string
	APIKey        string
	HTTPClient    *http.Client
}

// NewClient builds an HTTP Fetcher. When Enabled is false, Fetch is a no-op.
func NewClient(opts Options) *Client {
	timeout := opts.Timeout
	if timeout <= 0 {
		timeout = defaultTimeout
	}
	base := strings.TrimRight(strings.TrimSpace(opts.BaseURL), "/")
	if base == "" {
		base = defaultBaseURL
	}
	lang := strings.TrimSpace(opts.FicheLanguage)
	if lang == "" {
		lang = defaultFicheLanguage
	} else {
		lang = strings.ToUpper(lang)
		if !isAllowedFicheLanguage(lang) {
			lang = defaultFicheLanguage
		}
	}
	httpClient := opts.HTTPClient
	if httpClient == nil {
		httpClient = security.SafeHTTPClient(timeout, false)
	} else if httpClient.Timeout == 0 {
		cloned := *httpClient
		cloned.Timeout = timeout
		httpClient = &cloned
	}
	return &Client{
		BaseURL:       base,
		FicheLanguage: lang,
		APIKey:        strings.TrimSpace(opts.APIKey),
		HTTP:          httpClient,
		enabled:       opts.Enabled,
	}
}

// Enabled reports whether EPREL enrichment is active.
func (c *Client) Enabled() bool {
	return c != nil && c.enabled
}

// Fetch loads label URL, product fiche PDF, and energy class for a registration id.
// Partial success is returned when some sub-calls fail (label URL is always set for a valid id).
func (c *Client) Fetch(ctx context.Context, eprelID string) (*Data, error) {
	if !c.Enabled() {
		return nil, nil
	}
	id := NormalizeID(eprelID)
	if id == "" {
		return nil, nil
	}
	if err := validateID(id); err != nil {
		return nil, err
	}

	out := &Data{
		ID:    id,
		Label: fmt.Sprintf("%s/product/%s/labels?format=png", c.BaseURL, url.PathEscape(id)),
	}

	if pdf, err := c.fetchFichePDF(ctx, id); err == nil && pdf != "" {
		out.PDF = pdf
	}
	if class, scale, err := c.fetchProductInfo(ctx, id); err == nil {
		out.EnergyClass = class
		out.EnergyScale = scale
	}
	return out, nil
}

func validateID(id string) error {
	if len(id) > 64 {
		return fmt.Errorf("eprel id too long")
	}
	for _, r := range id {
		if (r >= '0' && r <= '9') || (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || r == '-' || r == '_' {
			continue
		}
		return fmt.Errorf("eprel id has invalid characters")
	}
	return nil
}

func (c *Client) fetchFichePDF(ctx context.Context, id string) (string, error) {
	path := fmt.Sprintf("/product/%s/fiches", url.PathEscape(id))
	q := url.Values{}
	q.Set("noRedirect", "true")
	q.Set("language", c.FicheLanguage)
	raw, err := c.get(ctx, path, q)
	if err != nil {
		return "", err
	}
	var payload struct {
		Address string `json:"address"`
	}
	if err := json.Unmarshal(raw, &payload); err != nil {
		return "", err
	}
	addr := strings.TrimSpace(payload.Address)
	if addr == "" {
		return "", nil
	}
	if strings.HasPrefix(addr, "http://") || strings.HasPrefix(addr, "https://") {
		return addr, nil
	}
	if !strings.HasPrefix(addr, "/") {
		addr = "/" + addr
	}
	origin := originFromBase(c.BaseURL)
	return origin + addr, nil
}

func (c *Client) fetchProductInfo(ctx context.Context, id string) (class, scale string, err error) {
	raw, err := c.get(ctx, fmt.Sprintf("/product/%s", url.PathEscape(id)), nil)
	if err != nil {
		return "", "", err
	}
	var payload struct {
		EnergyClass      string `json:"energyClass"`
		EnergyClassRange string `json:"energyClassRange"`
		EnergyScale      string `json:"energyScale"`
	}
	if err := json.Unmarshal(raw, &payload); err != nil {
		return "", "", err
	}
	class = strings.ReplaceAll(strings.TrimSpace(payload.EnergyClass), "_", "-")
	scale = strings.TrimSpace(payload.EnergyClassRange)
	if scale == "" {
		scale = strings.TrimSpace(payload.EnergyScale)
	}
	return class, scale, nil
}

func (c *Client) get(ctx context.Context, path string, query url.Values) ([]byte, error) {
	u, err := url.Parse(c.BaseURL + path)
	if err != nil {
		return nil, err
	}
	if query != nil {
		u.RawQuery = query.Encode()
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u.String(), nil)
	if err != nil {
		return nil, err
	}
	req.Header.Set("Accept", "application/json")
	req.Header.Set("User-Agent", "Descrybe-EPREL/2.0")
	if c.APIKey != "" {
		req.Header.Set("X-API-KEY", c.APIKey)
	}
	res, err := c.HTTP.Do(req)
	if err != nil {
		return nil, err
	}
	defer res.Body.Close()
	limited := io.LimitReader(res.Body, maxBodyBytes+1)
	raw, err := io.ReadAll(limited)
	if err != nil {
		return nil, err
	}
	if len(raw) > maxBodyBytes {
		return nil, fmt.Errorf("eprel response too large")
	}
	if res.StatusCode < 200 || res.StatusCode >= 300 {
		return nil, fmt.Errorf("eprel api %s", strconv.Itoa(res.StatusCode))
	}
	return raw, nil
}

func originFromBase(base string) string {
	u, err := url.Parse(base)
	if err != nil || u.Scheme == "" || u.Host == "" {
		return "https://eprel.ec.europa.eu"
	}
	return u.Scheme + "://" + u.Host
}

// AttributeKeys are the processed_attributes keys written for exports/mapping.
const (
	AttrID          = "eprel_id"
	AttrLabel       = "eprel_label"
	AttrLabelURL    = "eprel_label_url"
	AttrPDF         = "eprel_pdf"
	AttrPDFURL      = "eprel_pdf_url"
	AttrEnergyClass = "eprel_energy_class"
	AttrEnergyScale = "eprel_energy_scale"
)

// MergeInto copies EPREL fields into dest (creates map if nil). Returns dest.
// Writes both flat eprel_* keys (export mapping) and a nested "eprel" object (API shape).
func MergeInto(dest map[string]any, data *Data) map[string]any {
	if data == nil || data.ID == "" {
		return dest
	}
	if dest == nil {
		dest = map[string]any{}
	}
	dest[AttrID] = data.ID
	if data.Label != "" {
		dest[AttrLabel] = data.Label
		dest[AttrLabelURL] = data.Label
	}
	if data.PDF != "" {
		dest[AttrPDF] = data.PDF
		dest[AttrPDFURL] = data.PDF
	}
	if data.EnergyClass != "" {
		dest[AttrEnergyClass] = data.EnergyClass
	}
	if data.EnergyScale != "" {
		dest[AttrEnergyScale] = data.EnergyScale
	}
	nested := map[string]any{
		"id":    data.ID,
		"label": data.Label,
	}
	if data.PDF != "" {
		nested["pdf"] = data.PDF
	}
	if data.EnergyClass != "" {
		nested["energy_class"] = data.EnergyClass
	}
	if data.EnergyScale != "" {
		nested["energy_scale"] = data.EnergyScale
	}
	dest["eprel"] = nested
	return dest
}

// FieldValue returns a single export field from Data (empty when missing).
func FieldValue(data *Data, fieldName string) string {
	if data == nil {
		return ""
	}
	switch strings.ToLower(strings.TrimSpace(fieldName)) {
	case AttrID, "eprelid":
		return data.ID
	case AttrLabel, AttrLabelURL:
		return data.Label
	case AttrPDF, AttrPDFURL:
		return data.PDF
	case AttrEnergyClass:
		return data.EnergyClass
	case AttrEnergyScale:
		return data.EnergyScale
	default:
		return ""
	}
}

// Disabled is a no-op Fetcher used when EPREL_ENABLED is false.
type Disabled struct{}

func (Disabled) Enabled() bool { return false }

func (Disabled) Fetch(context.Context, string) (*Data, error) { return nil, nil }