// Package asnresolve fetches IP prefixes announced by an ASN (control-plane ingest).
package asnresolve

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/netip"
	"os"
	"sort"
	"strings"

	"evobgp/internal/httpclient"
)

// DefaultRIPEStatURL is the RIPEstat announced-prefixes data call (no API key).
const DefaultRIPEStatURL = "https://stat.ripe.net/data/announced-prefixes/data.json"

// DefaultASOverviewURL is the RIPEstat as-overview data call (holder / org name, no API key).
const DefaultASOverviewURL = "https://stat.ripe.net/data/as-overview/data.json"

// AnnouncedPrefixes returns currently announced IPv4/IPv6 prefixes for the ASN (best-effort via RIPEstat).
func AnnouncedPrefixes(ctx context.Context, hc *http.Client, asn int64) ([]netip.Prefix, error) {
	if hc == nil {
		hc = httpclient.New(httpclient.DefaultTimeout)
	}
	base := strings.TrimSpace(os.Getenv("EVOBGP_RIPESTAT_ANNOUNCED_PREFIXES_URL"))
	if base == "" {
		base = DefaultRIPEStatURL
	}
	u := fmt.Sprintf("%s?resource=AS%d", strings.TrimSuffix(base, "?"), asn)
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
	if err != nil {
		return nil, err
	}
	req.Header.Set("Accept", "application/json")
	req.Header.Set("User-Agent", "evobgp-asnresolve/1.0")

	resp, err := httpclient.DoWithBreaker(ctx, hc, req, 3)
	if err != nil {
		return nil, fmt.Errorf("ripestat fetch AS%d: %w", asn, err)
	}
	defer func() { _ = resp.Body.Close() }()
	body, err := io.ReadAll(io.LimitReader(resp.Body, 32<<20))
	if err != nil {
		return nil, err
	}
	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("ripestat AS%d: HTTP %s: %s", asn, resp.Status, truncateForErr(body, 200))
	}

	var wrap struct {
		Status string `json:"status"`
		Data   struct {
			Prefixes []struct {
				Prefix string `json:"prefix"`
			} `json:"prefixes"`
		} `json:"data"`
		Messages [][]string `json:"messages"`
	}
	if err := json.Unmarshal(body, &wrap); err != nil {
		return nil, fmt.Errorf("ripestat AS%d: json: %w", asn, err)
	}
	if wrap.Status != "" && wrap.Status != "ok" {
		return nil, fmt.Errorf("ripestat AS%d: status %q", asn, wrap.Status)
	}

	var out []netip.Prefix
	for _, row := range wrap.Data.Prefixes {
		p := strings.TrimSpace(row.Prefix)
		if p == "" {
			continue
		}
		pfx, err := netip.ParsePrefix(p)
		if err != nil {
			continue
		}
		out = append(out, pfx.Masked())
	}
	sort.Slice(out, func(i, j int) bool { return out[i].String() < out[j].String() })
	return out, nil
}

// ASHolderName returns the holder / organization label for the ASN from RIPEstat as-overview (best-effort).
func ASHolderName(ctx context.Context, hc *http.Client, asn int64) (string, error) {
	if hc == nil {
		hc = httpclient.New(httpclient.DefaultTimeout)
	}
	base := strings.TrimSpace(os.Getenv("EVOBGP_RIPESTAT_AS_OVERVIEW_URL"))
	if base == "" {
		base = DefaultASOverviewURL
	}
	u := fmt.Sprintf("%s?resource=AS%d", strings.TrimSuffix(base, "?"), asn)
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
	if err != nil {
		return "", err
	}
	req.Header.Set("Accept", "application/json")
	req.Header.Set("User-Agent", "evobgp-asnresolve/1.0")

	resp, err := httpclient.DoWithBreaker(ctx, hc, req, 3)
	if err != nil {
		return "", fmt.Errorf("ripestat as-overview AS%d: %w", asn, err)
	}
	defer func() { _ = resp.Body.Close() }()
	body, err := io.ReadAll(io.LimitReader(resp.Body, 4<<20))
	if err != nil {
		return "", err
	}
	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("ripestat as-overview AS%d: HTTP %s: %s", asn, resp.Status, truncateForErr(body, 200))
	}

	var wrap struct {
		Status string `json:"status"`
		Data   struct {
			Holder string `json:"holder"`
		} `json:"data"`
	}
	if err := json.Unmarshal(body, &wrap); err != nil {
		return "", fmt.Errorf("ripestat as-overview AS%d: json: %w", asn, err)
	}
	if wrap.Status != "" && wrap.Status != "ok" {
		return "", fmt.Errorf("ripestat as-overview AS%d: status %q", asn, wrap.Status)
	}
	return strings.TrimSpace(wrap.Data.Holder), nil
}

func truncateForErr(b []byte, n int) string {
	s := string(b)
	if len(s) > n {
		return s[:n] + "…"
	}
	return s
}