package api

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"regexp"
	"strconv"
	"strings"
	"time"

	"github.com/intodns/backend/internal/checker"
	"github.com/intodns/backend/internal/store"
)

var validHostname = regexp.MustCompile(`^([a-zA-Z0-9]([a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])?\.)+[a-zA-Z]{2,}$`)

func cleanDomain(raw string) string {
	domain := raw
	domain = strings.TrimPrefix(domain, "http://")
	domain = strings.TrimPrefix(domain, "https://")
	domain = strings.TrimRight(domain, "/")
	if idx := strings.Index(domain, "/"); idx != -1 {
		domain = domain[:idx]
	}
	if idx := strings.LastIndex(domain, ":"); idx != -1 {
		domain = domain[:idx]
	}
	return strings.ToLower(strings.TrimSpace(domain))
}

// CheckHandler returns the full report as JSON (non-streaming).
func CheckHandler(ch *checker.Checker, st *store.Store) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		domain := cleanDomain(r.URL.Query().Get("domain"))
		if domain == "" {
			writeJSON(w, http.StatusBadRequest, ErrorResponse{Error: "missing 'domain' query parameter"})
			return
		}
		if !validHostname.MatchString(domain) {
			writeJSON(w, http.StatusBadRequest, ErrorResponse{Error: "invalid domain name"})
			return
		}

		report := ch.Check(domain)

		if st != nil {
			if err := st.SaveReport(report, extractIP(r), r.UserAgent()); err != nil {
				log.Printf("failed to save report: %v", err)
			}
		}

		writeJSON(w, http.StatusOK, report)
	}
}

// CheckStreamHandler streams results via Server-Sent Events as each category completes.
func CheckStreamHandler(ch *checker.Checker, st *store.Store) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		domain := cleanDomain(r.URL.Query().Get("domain"))
		if domain == "" {
			writeJSON(w, http.StatusBadRequest, ErrorResponse{Error: "missing 'domain' query parameter"})
			return
		}
		if !validHostname.MatchString(domain) {
			writeJSON(w, http.StatusBadRequest, ErrorResponse{Error: "invalid domain name"})
			return
		}

		flusher, ok := w.(http.Flusher)
		if !ok {
			// Fallback to non-streaming.
			report := ch.Check(domain)
			if st != nil {
				if err := st.SaveReport(report, extractIP(r), r.UserAgent()); err != nil {
					log.Printf("failed to save report: %v", err)
				}
			}
			writeJSON(w, http.StatusOK, report)
			return
		}

		w.Header().Set("Content-Type", "text/event-stream")
		w.Header().Set("Cache-Control", "no-cache")
		w.Header().Set("Connection", "keep-alive")
		w.Header().Set("X-Accel-Buffering", "no")
		w.WriteHeader(http.StatusOK)
		flusher.Flush()

		start := time.Now()
		catCh := ch.CheckStream(domain)
		var categories []checker.Category
		for event := range catCh {
			categories = append(categories, event.Category)
			data, err := json.Marshal(event)
			if err != nil {
				continue
			}
			fmt.Fprintf(w, "data: %s\n\n", data)
			flusher.Flush()
		}

		// Build and save the final report.
		if st != nil {
			var summary checker.Summary
			for _, cat := range categories {
				for _, check := range cat.Checks {
					switch check.Status {
					case checker.StatusPass:
						summary.Pass++
					case checker.StatusWarn:
						summary.Warn++
					case checker.StatusFail:
						summary.Fail++
					case checker.StatusInfo:
						summary.Info++
					}
				}
			}
			report := &checker.Report{
				Domain:     domain,
				Timestamp:  time.Now().UTC().Format(time.RFC3339),
				DurationMs: time.Since(start).Milliseconds(),
				Summary:    summary,
				Categories: categories,
			}
			if err := st.SaveReport(report, extractIP(r), r.UserAgent()); err != nil {
				log.Printf("failed to save streamed report: %v", err)
			}
		}

		fmt.Fprintf(w, "data: {\"done\":true}\n\n")
		flusher.Flush()
	}
}

// HistoryHandler returns recent check history as JSON.
// Query params: domain (optional), limit (default 20, max 100).
func HistoryHandler(st *store.Store) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		domain := r.URL.Query().Get("domain")
		limitStr := r.URL.Query().Get("limit")

		limit := 20
		if limitStr != "" {
			if n, err := strconv.Atoi(limitStr); err == nil && n > 0 {
				limit = n
			}
		}
		if limit > 100 {
			limit = 100
		}

		var entries []store.HistoryEntry
		var err error

		if domain != "" {
			entries, err = st.GetHistory(domain, limit)
		} else {
			entries, err = st.GetRecent(limit)
		}

		if err != nil {
			log.Printf("history query error: %v", err)
			writeJSON(w, http.StatusInternalServerError, ErrorResponse{Error: "failed to query history"})
			return
		}

		if entries == nil {
			entries = []store.HistoryEntry{}
		}

		writeJSON(w, http.StatusOK, entries)
	}
}

// ReportHandler returns the full saved report JSON for a specific history entry.
// Query param: id (required).
func ReportHandler(st *store.Store) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		idStr := r.URL.Query().Get("id")
		if idStr == "" {
			writeJSON(w, http.StatusBadRequest, ErrorResponse{Error: "missing 'id' query parameter"})
			return
		}

		id, err := strconv.ParseInt(idStr, 10, 64)
		if err != nil {
			writeJSON(w, http.StatusBadRequest, ErrorResponse{Error: "invalid 'id' parameter"})
			return
		}

		entry, err := st.GetReport(id)
		if err != nil {
			log.Printf("report query error: %v", err)
			writeJSON(w, http.StatusInternalServerError, ErrorResponse{Error: "failed to query report"})
			return
		}
		if entry == nil {
			writeJSON(w, http.StatusNotFound, ErrorResponse{Error: "report not found"})
			return
		}

		writeJSON(w, http.StatusOK, entry)
	}
}

// HealthHandler returns an http.HandlerFunc for the health endpoint.
func HealthHandler() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		writeJSON(w, http.StatusOK, HealthResponse{Status: "ok"})
	}
}

func writeJSON(w http.ResponseWriter, status int, v interface{}) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	json.NewEncoder(w).Encode(v)
}