package checker

import (
	"bufio"
	"compress/gzip"
	"context"
	"encoding/csv"
	"fmt"
	"io"
	"net/http"
	"strconv"
	"strings"
	"time"

	sdk "git.happydns.org/checker-sdk-go/checker"
)

const (
	phishTankFeedURL    = "https://data.phishtank.com/data/online-valid.csv.gz"
	phishTankDefaultTTL = 12 * time.Hour
)

var phishTankGlobalCache = newFeedCache(phishTankDefaultTTL, phishTankFetch)

func init() { Register(&phishTankSource{}) }

type phishTankSource struct{}

func (*phishTankSource) ID() string   { return "phishtank" }
func (*phishTankSource) Name() string { return "PhishTank" }

func (*phishTankSource) Options() SourceOptions {
	return SourceOptions{
		Admin: []sdk.CheckerOptionField{
			{
				Id:          "phishtank_refresh_hours",
				Type:        "string",
				Label:       "PhishTank feed refresh interval (hours)",
				Description: "How often to re-download the PhishTank online-valid feed. Minimum: 1. Default: 12.",
				Default:     "12",
			},
		},
		User: []sdk.CheckerOptionField{
			{
				Id:          "enable_phishtank",
				Type:        "bool",
				Label:       "Use the PhishTank feed",
				Description: "Download the PhishTank verified phishing list and check the domain against it.",
				Default:     true,
			},
		},
	}
}

func (s *phishTankSource) Query(ctx context.Context, domain, registered string, opts sdk.CheckerOptions) []SourceResult {
	if !sdk.GetBoolOption(opts, "enable_phishtank", true) || registered == "" {
		return disabledResult(s.ID(), s.Name())
	}

	if ttlRaw, ok := sdk.GetOption[string](opts, "phishtank_refresh_hours"); ok && ttlRaw != "" {
		if hours, err := strconv.Atoi(ttlRaw); err == nil && hours >= 1 {
			phishTankGlobalCache.setTTL(time.Duration(hours) * time.Hour)
		}
	}

	urls, size, fetched, err := phishTankGlobalCache.lookup(ctx, registered)
	res := SourceResult{
		SourceID: s.ID(), SourceName: s.Name(), Enabled: true,
		Reference: "https://www.phishtank.com/",
		Details:   mustJSON(map[string]any{"feed_size": size, "fetched_at": fetched}),
	}
	if err != nil {
		res.Error = err.Error()
	}
	if len(urls) > 0 {
		res.Reasons = []string{"Phishing"}
		for _, u := range urls {
			res.Evidence = append(res.Evidence, Evidence{Label: "URL", Value: u})
		}
	}
	return []SourceResult{res}
}

func (*phishTankSource) Evaluate(r SourceResult) (bool, string) {
	return evidenceEval(r, SeverityCrit)
}

func (*phishTankSource) Diagnose(res SourceResult) Diagnosis {
	urls := make([]string, 0, len(res.Evidence))
	for _, e := range res.Evidence {
		urls = append(urls, e.Value)
	}
	previewN := min(len(urls), 5)
	return Diagnosis{
		Severity: SeverityCrit,
		Title:    "Listed in the PhishTank phishing database",
		Detail: fmt.Sprintf(
			"%d URL(s) hosted on this domain are tracked as verified phishing by PhishTank. Examples: %s",
			len(urls), joinNonEmpty(urls[:previewN], ", "),
		),
		Fix:      "https://www.phishtank.com/developer_info.php",
		FixIsURL: true,
	}
}

// phishTankFetch downloads and parses the PhishTank gzip-compressed CSV feed.
func phishTankFetch(ctx context.Context) ([]string, map[string][]string, error) {
	reqCtx, cancel := context.WithTimeout(ctx, 120*time.Second)
	defer cancel()

	req, err := http.NewRequestWithContext(reqCtx, http.MethodGet, phishTankFeedURL, nil)
	if err != nil {
		return nil, nil, err
	}
	req.Header.Set("User-Agent", "happydomain-checker-blacklist/1.0")

	resp, err := sharedHTTPClient.Do(req)
	if err != nil {
		return nil, nil, err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, nil, fmt.Errorf("phishtank HTTP %d", resp.StatusCode)
	}

	gz, err := gzip.NewReader(io.LimitReader(resp.Body, 128<<20))
	if err != nil {
		return nil, nil, fmt.Errorf("phishtank gzip: %w", err)
	}
	defer gz.Close()

	r := csv.NewReader(bufio.NewReader(gz))
	r.ReuseRecord = true

	header, err := r.Read()
	if err != nil {
		return nil, nil, fmt.Errorf("phishtank csv header: %w", err)
	}
	urlIdx := -1
	for i, col := range header {
		if col == "url" {
			urlIdx = i
			break
		}
	}
	if urlIdx < 0 {
		return nil, nil, fmt.Errorf("phishtank csv: no 'url' column in header")
	}

	urls := make([]string, 0, 32768)
	byHost := make(map[string][]string, 32768)
	for {
		record, err := r.Read()
		if err == io.EOF {
			break
		}
		if err != nil {
			return nil, nil, fmt.Errorf("phishtank csv: %w", err)
		}
		if urlIdx >= len(record) {
			continue
		}
		u := strings.TrimSpace(record[urlIdx])
		if u == "" {
			continue
		}
		urls = append(urls, u)
		if h := hostOfURL(u); h != "" {
			byHost[h] = append(byHost[h], u)
		}
	}
	return urls, byHost, nil
}