package opnsense

import (
	"bytes"
	"context"
	"crypto/tls"
	"encoding/json"
	"fmt"
	"io"
	"net"
	"net/http"
	"net/url"
	"strings"
	"sync"

	"git.dern.ovh/infrastructure/caddy-opnsense-blocker/internal/config"
)

type AliasClient interface {
	AddIPIfMissing(ctx context.Context, ip string) (string, error)
	RemoveIPIfPresent(ctx context.Context, ip string) (string, error)
	IsIPPresent(ctx context.Context, ip string) (bool, error)
}

type Client struct {
	cfg        config.OPNsenseConfig
	httpClient *http.Client

	mu            sync.Mutex
	aliasUUID     string
	knownAliasIPs map[string]struct{}
}

func NewClient(cfg config.OPNsenseConfig) *Client {
	transport := &http.Transport{
		TLSClientConfig: &tls.Config{InsecureSkipVerify: cfg.InsecureSkipVerify},
	}

	return &Client{
		cfg: cfg,
		httpClient: &http.Client{
			Timeout:   cfg.Timeout.Duration,
			Transport: transport,
		},
	}
}

func (c *Client) AddIPIfMissing(ctx context.Context, ip string) (string, error) {
	normalized, err := normalizeIP(ip)
	if err != nil {
		return "", err
	}

	c.mu.Lock()
	defer c.mu.Unlock()

	snapshot, err := c.ensureAliasSnapshotLocked(ctx)
	if err != nil {
		return "", err
	}
	if _, ok := snapshot[normalized]; ok {
		return "already_present", nil
	}

	payload, err := c.requestJSON(ctx, http.MethodPost, c.cfg.APIPaths.AliasUtilAdd, map[string]string{"alias": c.cfg.Alias.Name}, map[string]string{"address": normalized})
	if err != nil {
		return "", err
	}
	if status := strings.ToLower(strings.TrimSpace(asString(payload["status"]))); status != "done" {
		return "", fmt.Errorf("opnsense alias add failed: %v", payload)
	}
	snapshot[normalized] = struct{}{}
	return "added", nil
}

func (c *Client) RemoveIPIfPresent(ctx context.Context, ip string) (string, error) {
	normalized, err := normalizeIP(ip)
	if err != nil {
		return "", err
	}

	c.mu.Lock()
	defer c.mu.Unlock()

	snapshot, err := c.ensureAliasSnapshotLocked(ctx)
	if err != nil {
		return "", err
	}
	if _, ok := snapshot[normalized]; !ok {
		return "already_absent", nil
	}

	payload, err := c.requestJSON(ctx, http.MethodPost, c.cfg.APIPaths.AliasUtilDelete, map[string]string{"alias": c.cfg.Alias.Name}, map[string]string{"address": normalized})
	if err != nil {
		return "", err
	}
	if status := strings.ToLower(strings.TrimSpace(asString(payload["status"]))); status != "done" {
		return "", fmt.Errorf("opnsense alias delete failed: %v", payload)
	}
	delete(snapshot, normalized)
	return "removed", nil
}

func (c *Client) IsIPPresent(ctx context.Context, ip string) (bool, error) {
	normalized, err := normalizeIP(ip)
	if err != nil {
		return false, err
	}

	c.mu.Lock()
	defer c.mu.Unlock()

	snapshot, err := c.ensureAliasSnapshotLocked(ctx)
	if err != nil {
		return false, err
	}
	_, ok := snapshot[normalized]
	return ok, nil
}

func (c *Client) ensureAliasSnapshotLocked(ctx context.Context) (map[string]struct{}, error) {
	if c.knownAliasIPs != nil {
		return c.knownAliasIPs, nil
	}
	if err := c.ensureAliasExistsLocked(ctx); err != nil {
		return nil, err
	}
	payload, err := c.requestJSON(ctx, http.MethodGet, c.cfg.APIPaths.AliasUtilList, map[string]string{"alias": c.cfg.Alias.Name}, nil)
	if err != nil {
		return nil, err
	}
	rows, ok := payload["rows"].([]any)
	if !ok {
		return nil, fmt.Errorf("unexpected opnsense alias listing payload: %v", payload)
	}
	snapshot := make(map[string]struct{}, len(rows))
	for _, row := range rows {
		rowMap, ok := row.(map[string]any)
		if !ok {
			return nil, fmt.Errorf("unexpected opnsense alias row payload: %T", row)
		}
		candidate := asString(rowMap["ip"])
		if candidate == "" {
			candidate = asString(rowMap["address"])
		}
		if candidate == "" {
			candidate = asString(rowMap["item"])
		}
		if candidate == "" {
			continue
		}
		normalized, err := normalizeIP(candidate)
		if err != nil {
			continue
		}
		snapshot[normalized] = struct{}{}
	}
	c.knownAliasIPs = snapshot
	return snapshot, nil
}

func (c *Client) ensureAliasExistsLocked(ctx context.Context) error {
	if c.aliasUUID != "" {
		return nil
	}

	uuid, err := c.getAliasUUIDLocked(ctx)
	if err != nil {
		return err
	}
	if uuid == "" {
		if !c.cfg.EnsureAlias {
			return fmt.Errorf("opnsense alias %q does not exist and ensure_alias is disabled", c.cfg.Alias.Name)
		}
		if _, err := c.requestJSON(ctx, http.MethodPost, c.cfg.APIPaths.AliasAddItem, nil, map[string]any{
			"alias": map[string]string{
				"enabled":     "1",
				"name":        c.cfg.Alias.Name,
				"type":        c.cfg.Alias.Type,
				"content":     "",
				"description": c.cfg.Alias.Description,
			},
		}); err != nil {
			return err
		}
		uuid, err = c.getAliasUUIDLocked(ctx)
		if err != nil {
			return err
		}
		if uuid == "" {
			return fmt.Errorf("unable to create opnsense alias %q", c.cfg.Alias.Name)
		}
		if _, err := c.requestJSON(ctx, http.MethodPost, c.cfg.APIPaths.AliasSetItem, map[string]string{"uuid": uuid}, map[string]any{
			"alias": map[string]string{
				"enabled":     "1",
				"name":        c.cfg.Alias.Name,
				"type":        c.cfg.Alias.Type,
				"content":     "",
				"description": c.cfg.Alias.Description,
			},
		}); err != nil {
			return err
		}
		if err := c.reconfigureLocked(ctx); err != nil {
			return err
		}
	}
	c.aliasUUID = uuid
	return nil
}

func (c *Client) getAliasUUIDLocked(ctx context.Context) (string, error) {
	payload, err := c.requestJSON(ctx, http.MethodGet, c.cfg.APIPaths.AliasGetUUID, map[string]string{"alias": c.cfg.Alias.Name}, nil)
	if err != nil {
		return "", err
	}
	return strings.TrimSpace(asString(payload["uuid"])), nil
}

func (c *Client) reconfigureLocked(ctx context.Context) error {
	payload, err := c.requestJSON(ctx, http.MethodPost, c.cfg.APIPaths.AliasReconfig, nil, nil)
	if err != nil {
		return err
	}
	status := strings.ToLower(strings.TrimSpace(asString(payload["status"])))
	if status != "ok" && status != "done" {
		return fmt.Errorf("opnsense alias reconfigure failed: %v", payload)
	}
	return nil
}

func (c *Client) requestJSON(ctx context.Context, method, pathTemplate string, pathValues map[string]string, body any) (map[string]any, error) {
	requestURL, err := c.buildURL(pathTemplate, pathValues)
	if err != nil {
		return nil, err
	}

	var payload io.Reader
	if body != nil {
		encoded, err := json.Marshal(body)
		if err != nil {
			return nil, fmt.Errorf("encode request body: %w", err)
		}
		payload = bytes.NewReader(encoded)
	}

	req, err := http.NewRequestWithContext(ctx, method, requestURL, payload)
	if err != nil {
		return nil, fmt.Errorf("build request: %w", err)
	}
	req.SetBasicAuth(c.cfg.APIKey, c.cfg.APISecret)
	req.Header.Set("Accept", "application/json")
	if body != nil {
		req.Header.Set("Content-Type", "application/json")
	}

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("perform request: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		payload, _ := io.ReadAll(io.LimitReader(resp.Body, 8<<10))
		return nil, fmt.Errorf("unexpected status %s: %s", resp.Status, strings.TrimSpace(string(payload)))
	}

	var decoded map[string]any
	if err := json.NewDecoder(resp.Body).Decode(&decoded); err != nil {
		return nil, fmt.Errorf("decode response: %w", err)
	}
	return decoded, nil
}

func (c *Client) buildURL(pathTemplate string, values map[string]string) (string, error) {
	baseURL := strings.TrimRight(c.cfg.BaseURL, "/")
	if baseURL == "" {
		return "", fmt.Errorf("missing opnsense base url")
	}
	path := pathTemplate
	for key, value := range values {
		path = strings.ReplaceAll(path, "{"+key+"}", url.PathEscape(value))
	}
	return baseURL + path, nil
}

func normalizeIP(ip string) (string, error) {
	parsed := net.ParseIP(strings.TrimSpace(ip))
	if parsed == nil {
		return "", fmt.Errorf("invalid ip address %q", ip)
	}
	return parsed.String(), nil
}

func asString(value any) string {
	switch typed := value.(type) {
	case string:
		return typed
	case fmt.Stringer:
		return typed.String()
	case nil:
		return ""
	default:
		return fmt.Sprintf("%v", typed)
	}
}