package collector

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"time"

	"git.tornberg.me/go-otel/internal/storage"
)

const (
	// CSP reports are small; URLs and the echoed policy are the long parts.
	maxCSPBody       = 16 << 10
	maxCSPURL        = 512
	maxCSPPolicy     = 2048
	maxCSPSample     = 300
	maxCSPBatch      = 50
	defaultCSPWindow = 24
)

// SetCSPStore enables CSP violation report collection. Both the ClickHouse
// store and the file fallback satisfy the interface; nil disables the
// endpoints.
func (c *Collector) SetCSPStore(s storage.CSPStore) { c.cspStore = s }

// cspReportBody mirrors the legacy report-uri payload
// (Content-Type: application/csp-report).
type cspReportBody struct {
	CSPReport struct {
		DocumentURI        string `json:"document-uri"`
		Referrer           string `json:"referrer"`
		BlockedURI         string `json:"blocked-uri"`
		ViolatedDirective  string `json:"violated-directive"`
		EffectiveDirective string `json:"effective-directive"`
		OriginalPolicy     string `json:"original-policy"`
		Disposition        string `json:"disposition"`
		StatusCode         int    `json:"status-code"`
		ScriptSample       string `json:"script-sample"`
	} `json:"csp-report"`
}

// cspAPIReport mirrors one entry of the Reporting API payload
// (Content-Type: application/reports+json); body repeats the csp-report
// fields in camelCase.
type cspAPIReport struct {
	Type      string `json:"type"`
	UserAgent string `json:"user_agent"`
	Body      struct {
		DocumentURL        string `json:"documentURL"`
		Referrer           string `json:"referrer"`
		BlockedURL         string `json:"blockedURL"`
		ViolatedDirective  string `json:"violatedDirective"`
		EffectiveDirective string `json:"effectiveDirective"`
		OriginalPolicy     string `json:"originalPolicy"`
		Disposition        string `json:"disposition"`
		StatusCode         int    `json:"statusCode"`
		Sample             string `json:"sample"`
	} `json:"body"`
}

func clipCSP(s string, max int) string {
	if len(s) > max {
		return s[:max]
	}
	return s
}

// parseCSPReports decodes either wire format into normalized reports; an
// unrecognized shape returns nil (the handler rejects those).
func parseCSPReports(body []byte) []storage.CSPReport {
	var reports []storage.CSPReport
	if len(body) > 0 && body[0] == '[' {
		var api []cspAPIReport
		if err := json.Unmarshal(body, &api); err != nil || len(api) == 0 {
			return nil
		}
		if len(api) > maxCSPBatch {
			api = api[:maxCSPBatch]
		}
		for _, r := range api {
			// The endpoint only serves CSP; skip other report types instead
			// of guessing at their bodies, and drop empty entries.
			if r.Type != "" && r.Type != "csp-violation" {
				continue
			}
			if r.Body.DocumentURL == "" && r.Body.BlockedURL == "" && r.Body.EffectiveDirective == "" &&
				r.Body.ViolatedDirective == "" && r.Body.Sample == "" {
				continue
			}
			reports = append(reports, storage.CSPReport{
				DocumentURL:        clipCSP(r.Body.DocumentURL, maxCSPURL),
				Referrer:           clipCSP(r.Body.Referrer, maxCSPURL),
				BlockedURL:         clipCSP(r.Body.BlockedURL, maxCSPURL),
				ViolatedDirective:  clipCSP(r.Body.ViolatedDirective, maxCSPSample),
				EffectiveDirective: clipCSP(r.Body.EffectiveDirective, maxCSPSample),
				OriginalPolicy:     clipCSP(r.Body.OriginalPolicy, maxCSPPolicy),
				Disposition:        clipCSP(r.Body.Disposition, 32),
				StatusCode:         r.Body.StatusCode,
				Sample:             clipCSP(r.Body.Sample, maxCSPSample),
				ReportType:         clipCSP(r.Type, 64),
				UserAgent:          clipCSP(r.UserAgent, maxCSPSample),
			})
		}
		return reports
	}

	var legacy cspReportBody
	if err := json.Unmarshal(body, &legacy); err != nil {
		return nil
	}
	v := legacy.CSPReport
	if v.DocumentURI == "" && v.BlockedURI == "" && v.ViolatedDirective == "" {
		return nil
	}
	return []storage.CSPReport{{
		DocumentURL:        clipCSP(v.DocumentURI, maxCSPURL),
		Referrer:           clipCSP(v.Referrer, maxCSPURL),
		BlockedURL:         clipCSP(v.BlockedURI, maxCSPURL),
		ViolatedDirective:  clipCSP(v.ViolatedDirective, maxCSPSample),
		EffectiveDirective: clipCSP(v.EffectiveDirective, maxCSPSample),
		OriginalPolicy:     clipCSP(v.OriginalPolicy, maxCSPPolicy),
		Disposition:        clipCSP(v.Disposition, 32),
		StatusCode:         v.StatusCode,
		Sample:             clipCSP(v.ScriptSample, maxCSPSample),
	}}
}

// finishCSPReport derives site/blocked host and a stable content id, and
// stamps server-side context (time, peer IP, request UA when the report
// carries none).
func finishCSPReport(r storage.CSPReport, now time.Time, peerIP, requestUA string) storage.CSPReport {
	if r.Site = storage.URLLowerHost(r.DocumentURL); r.Site == "" {
		r.Site = "unknown"
	}
	if r.ReportType == "" {
		r.ReportType = "csp-report"
	}
	if r.UserAgent == "" {
		r.UserAgent = clipCSP(requestUA, maxCSPSample)
	}
	r.SourceIP = peerIP
	r.Timestamp = now.UTC()
	// Deterministic id over the report content: a stable UI key that also
	// makes duplicate re-deliveries of one violation identifiable.
	hash := sha256.Sum256([]byte(fmt.Sprintf("%s|%s|%s|%s|%s|%s",
		r.Site, r.DocumentURL, r.BlockedURL, r.EffectiveDirective, r.Sample, r.Timestamp.Format(time.RFC3339Nano))))
	r.ID = hex.EncodeToString(hash[:8])
	return r
}

// HandleCSPIngest collects Content-Security-Policy violation reports posted
// by browsers (report-uri / report-to). Both the legacy application/csp-report
// object and the Reporting API's application/reports+json array are accepted.
// Browsers cannot attach auth headers, so like /v1/vitals the optional ingest
// key is accepted as ?key= on the configured reporting URL; CORS is limited
// to the operator's own domains (withReportingCORS in cmd/server).
func (c *Collector) HandleCSPIngest(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	if !c.checkIngest(w, r) {
		return
	}
	if c.cspStore == nil {
		http.Error(w, "csp report storage not configured", http.StatusServiceUnavailable)
		return
	}
	// Browsers post application/csp-report or application/reports+json; some
	// proxies rewrite the type, so decode regardless of content type.
	raw, err := io.ReadAll(http.MaxBytesReader(w, r.Body, maxCSPBody))
	if err != nil {
		http.Error(w, "invalid csp report payload", http.StatusBadRequest)
		return
	}
	reports := parseCSPReports(raw)
	if len(reports) == 0 {
		http.Error(w, "no csp reports in payload", http.StatusBadRequest)
		return
	}
	now := time.Now()
	peerIP := clientIP(r)
	requestUA := r.UserAgent()
	for i := range reports {
		reports[i] = finishCSPReport(reports[i], now, peerIP, requestUA)
	}
	ctx, cancel := context.WithTimeout(r.Context(), 10*time.Second)
	defer cancel()
	for _, report := range reports {
		if err := c.cspStore.AppendCSPReport(ctx, report); err != nil {
			log.Printf("csp: failed to store report: %v", err)
			http.Error(w, "failed to store report", http.StatusInternalServerError)
			return
		}
	}
	w.WriteHeader(http.StatusNoContent)
}

// HandleCSPReports serves the view's list.
// Query: site, directive, q (substring), hours, limit.
func (c *Collector) HandleCSPReports(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	if c.cspStore == nil {
		http.Error(w, "csp report storage not configured", http.StatusNotImplemented)
		return
	}
	q := storage.CSPReportsQuery{
		Site:      r.URL.Query().Get("site"),
		Directive: r.URL.Query().Get("directive"),
		Search:    r.URL.Query().Get("q"),
		Limit:     parseLimit(r, 200),
	}
	if _, hours := parseStatsCommon(r); r.URL.Query().Get("hours") != "" {
		q.Since = time.Now().Add(-time.Duration(hours) * time.Hour)
	}
	reports, err := c.cspStore.CSPReports(r.Context(), q)
	if err != nil {
		log.Printf("csp: list failed: %v", err)
		http.Error(w, "failed to list csp reports", http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(map[string]any{"reports": reports})
}

// HandleCSPSummary serves the view's aggregates. Query: hours (default 24).
func (c *Collector) HandleCSPSummary(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}
	if c.cspStore == nil {
		http.Error(w, "csp report storage not configured", http.StatusNotImplemented)
		return
	}
	_, hours := parseStatsCommon(r)
	if r.URL.Query().Get("hours") == "" {
		hours = defaultCSPWindow
	}
	summary, err := c.cspStore.CSPSummary(r.Context(), hours)
	if err != nil {
		log.Printf("csp: summary failed: %v", err)
		http.Error(w, "failed to summarize csp reports", http.StatusInternalServerError)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(map[string]any{"summary": summary})
}