package handlers

import (
	"context"
	"errors"
	"log/slog"
	"net"
	"net/http"
	"regexp"
	"strconv"
	"strings"

	"github.com/gin-gonic/gin"

	"git.netcell-it.de/projekte/edgeguard-native/internal/handlers/response"
	"git.netcell-it.de/projekte/edgeguard-native/internal/models"
	"git.netcell-it.de/projekte/edgeguard-native/internal/services/audit"
	wafsvc "git.netcell-it.de/projekte/edgeguard-native/internal/services/waf"
)

// wafRuleIDRe erlaubt nur einzelne CRS-Rule-IDs oder Ranges ("942100" /
// "942100-942999") als Exclusion — verhindert SecLang-Direktiven-Injection.
var wafRuleIDRe = regexp.MustCompile(`^[0-9]{1,9}(-[0-9]{1,9})?$`)

// WafHandler exposes the per-domain WAF configuration REST API:
//
//	GET    /waf/configs              — list all configs (one per domain)
//	GET    /waf/configs/:domain_id   — get config for a domain
//	PUT    /waf/configs/:domain_id   — upsert config for a domain
type WafHandler struct {
	Repo     *wafsvc.Repo
	Audit    *audit.Repo
	NodeID   string
	Reloader func(ctx context.Context) error
}

func NewWafHandler(repo *wafsvc.Repo, a *audit.Repo, nodeID string, reloader func(context.Context) error) *WafHandler {
	return &WafHandler{Repo: repo, Audit: a, NodeID: nodeID, Reloader: reloader}
}

func (h *WafHandler) Register(rg *gin.RouterGroup) {
	g := rg.Group("/waf")
	g.GET("/configs", h.List)
	g.GET("/configs/:domain_id", h.Get)
	g.PUT("/configs/:domain_id", h.Upsert)
	g.GET("/alerts", h.ListAlerts)
	g.DELETE("/alerts", h.PurgeAlerts)
}

// List returns all WAF configs.
func (h *WafHandler) List(c *gin.Context) {
	configs, err := h.Repo.List(c.Request.Context())
	if err != nil {
		response.Internal(c, err)
		return
	}
	response.OK(c, gin.H{"configs": configs})
}

// Get returns the WAF config for a single domain.
// Returns a default (disabled) config when none exists yet.
func (h *WafHandler) Get(c *gin.Context) {
	domainID, err := strconv.ParseInt(c.Param("domain_id"), 10, 64)
	if err != nil {
		response.BadRequest(c, errors.New("invalid domain_id"))
		return
	}
	cfg, err := h.Repo.GetByDomain(c.Request.Context(), domainID)
	if err != nil {
		if errors.Is(err, wafsvc.ErrNotFound) {
			// Return a default config so the UI always gets a usable object.
			response.OK(c, gin.H{"config": defaultConfig(domainID)})
			return
		}
		response.Internal(c, err)
		return
	}
	response.OK(c, gin.H{"config": cfg})
}

// upsertBody is the accepted JSON for PUT /waf/configs/:domain_id.
type upsertBody struct {
	Enabled         bool              `json:"enabled"`
	Mode            string            `json:"mode"`
	ParanoiaLevel   int               `json:"paranoia_level"`
	RuleExclusions  []string          `json:"rule_exclusions"`
	ExclusionNotes  map[string]string `json:"exclusion_notes"`
	TrustedProxies  []string          `json:"trusted_proxies"`
	CustomRules     string            `json:"custom_rules"`
}

// Upsert creates or updates the WAF config for a domain.
func (h *WafHandler) Upsert(c *gin.Context) {
	domainID, err := strconv.ParseInt(c.Param("domain_id"), 10, 64)
	if err != nil {
		response.BadRequest(c, errors.New("invalid domain_id"))
		return
	}
	var body upsertBody
	if err := c.ShouldBindJSON(&body); err != nil {
		response.BadRequest(c, err)
		return
	}
	if body.Mode == "" {
		body.Mode = "detection"
	}
	if body.ParanoiaLevel < 1 || body.ParanoiaLevel > 4 {
		body.ParanoiaLevel = 1
	}
	if body.RuleExclusions == nil {
		body.RuleExclusions = []string{}
	}
	if body.TrustedProxies == nil {
		body.TrustedProxies = []string{}
	}

	if body.ExclusionNotes == nil {
		body.ExclusionNotes = map[string]string{}
	}
	// Exclusions müssen reine Rule-IDs/Ranges sein (sonst Direktiven-Injection
	// in die SecLang-Config via Newline).
	for _, ex := range body.RuleExclusions {
		if !wafRuleIDRe.MatchString(strings.TrimSpace(ex)) {
			response.BadRequest(c, errors.New("ungültige Rule-Exclusion (nur IDs/Ranges erlaubt): "+ex))
			return
		}
	}
	// Trusted-Proxies müssen gültige IPs/CIDRs sein.
	for _, p := range body.TrustedProxies {
		p = strings.TrimSpace(p)
		if p == "" {
			continue
		}
		if net.ParseIP(p) == nil {
			if _, _, err := net.ParseCIDR(p); err != nil {
				response.BadRequest(c, errors.New("ungültiger Trusted-Proxy (IP/CIDR): "+p))
				return
			}
		}
	}
	cfg := models.WafConfig{
		DomainID:       domainID,
		Enabled:        body.Enabled,
		Mode:           body.Mode,
		ParanoiaLevel:  body.ParanoiaLevel,
		RuleExclusions: body.RuleExclusions,
		ExclusionNotes: body.ExclusionNotes,
		TrustedProxies: body.TrustedProxies,
		CustomRules:    body.CustomRules,
	}
	result, err := h.Repo.Upsert(c.Request.Context(), cfg)
	if err != nil {
		response.Internal(c, err)
		return
	}
	_ = h.Audit.Log(c.Request.Context(), actorOf(c), "waf.config.upsert",
		strconv.FormatInt(domainID, 10),
		gin.H{"enabled": body.Enabled, "mode": body.Mode, "paranoia_level": body.ParanoiaLevel},
		h.NodeID)
	// Reload HAProxy so the SPOE filter is added/removed based on
	// whether any domain now has WAF enabled.
	if h.Reloader != nil {
		go func() {
			if err := h.Reloader(context.Background()); err != nil {
				slog.Warn("waf: haproxy reload after config change failed", "error", err)
			}
		}()
	}
	c.JSON(http.StatusOK, gin.H{"config": result})
}

// ListAlerts returns recent WAF alerts. Optional: ?domain_id=X&limit=N
func (h *WafHandler) ListAlerts(c *gin.Context) {
	var domainID *int64
	if v := c.Query("domain_id"); v != "" {
		id, err := strconv.ParseInt(v, 10, 64)
		if err != nil {
			response.BadRequest(c, errors.New("invalid domain_id"))
			return
		}
		domainID = &id
	}
	limit := 200
	if v := c.Query("limit"); v != "" {
		if n, err := strconv.Atoi(v); err == nil && n > 0 {
			limit = n
		}
	}
	alerts, err := h.Repo.ListAlerts(c.Request.Context(), domainID, limit)
	if err != nil {
		response.Internal(c, err)
		return
	}
	response.OK(c, gin.H{"alerts": alerts})
}

// PurgeAlerts deletes old WAF alerts. Optional: ?days=N (default 30)
func (h *WafHandler) PurgeAlerts(c *gin.Context) {
	days := 30
	if v := c.Query("days"); v != "" {
		if n, err := strconv.Atoi(v); err == nil && n > 0 {
			days = n
		}
	}
	if err := h.Repo.PurgeAlerts(c.Request.Context(), days); err != nil {
		response.Internal(c, err)
		return
	}
	_ = h.Audit.Log(c.Request.Context(), actorOf(c), "waf.alerts.purge",
		"", gin.H{"days": days}, h.NodeID)
	response.OK(c, gin.H{"ok": true, "days": days})
}

// defaultConfig returns a sensible disabled default for a domain
// that has no WAF config row yet.
func defaultConfig(domainID int64) models.WafConfig {
	return models.WafConfig{
		DomainID:       domainID,
		Enabled:        false,
		Mode:           "detection",
		ParanoiaLevel:  1,
		RuleExclusions: []string{},
		ExclusionNotes: map[string]string{},
		TrustedProxies: []string{},
		CustomRules:    "",
	}
}