package verify

import (
	"bytes"
	"context"
	"crypto/tls"
	"io"
	"net/http"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/panjf2000/ants/v2"
	"github.com/salvacybersec/keyhunter/pkg/engine"
	"github.com/salvacybersec/keyhunter/pkg/providers"
	"github.com/tidwall/gjson"
)

// DefaultTimeout is the per-call verification timeout when none is configured.
const DefaultTimeout = 10 * time.Second

// DefaultWorkers is the fallback worker-pool size for VerifyAll.
const DefaultWorkers = 10

// maxMetadataBody caps how much of a JSON response we read for metadata extraction.
const maxMetadataBody = 1 << 20 // 1 MiB

// HTTPVerifier performs a single HTTP call against a provider's VerifySpec and
// classifies the response. It is YAML-driven — no per-provider switches live here.
type HTTPVerifier struct {
	Client  *http.Client
	Timeout time.Duration
}

// NewHTTPVerifier returns an HTTPVerifier with a TLS 1.2+ HTTP client and the
// given per-call timeout (falling back to DefaultTimeout when timeout <= 0).
func NewHTTPVerifier(timeout time.Duration) *HTTPVerifier {
	if timeout <= 0 {
		timeout = DefaultTimeout
	}
	return &HTTPVerifier{
		Client: &http.Client{
			Timeout: timeout,
			Transport: &http.Transport{
				TLSClientConfig: &tls.Config{MinVersion: tls.VersionTLS12},
			},
		},
		Timeout: timeout,
	}
}

// Verify runs a single verification against a provider's verify endpoint.
// It never returns a Go error — transport/classification failures are encoded
// in the Result. Callers classify via Result.Status against the Status* constants.
func (v *HTTPVerifier) Verify(ctx context.Context, f engine.Finding, p providers.Provider) Result {
	start := time.Now()
	res := Result{
		ProviderName: f.ProviderName,
		KeyMasked:    f.KeyMasked,
		Status:       StatusUnknown,
	}

	spec := p.Verify
	if spec.URL == "" {
		return res // StatusUnknown: provider has no verify endpoint
	}
	if strings.HasPrefix(strings.ToLower(spec.URL), "http://") {
		res.Status = StatusError
		res.Error = "verify URL must be HTTPS"
		return res
	}

	// Substitute {{KEY}} (and legacy {KEY}) in URL, headers, and body.
	url := substituteKey(spec.URL, f.KeyValue)

	method := spec.Method
	if method == "" {
		method = http.MethodGet
	}

	var bodyReader io.Reader
	if spec.Body != "" {
		bodyReader = bytes.NewBufferString(substituteKey(spec.Body, f.KeyValue))
	}

	reqCtx, cancel := context.WithTimeout(ctx, v.Timeout)
	defer cancel()

	req, err := http.NewRequestWithContext(reqCtx, method, url, bodyReader)
	if err != nil {
		res.Status = StatusError
		res.Error = err.Error()
		return res
	}
	for k, val := range spec.Headers {
		req.Header.Set(k, substituteKey(val, f.KeyValue))
	}

	resp, err := v.Client.Do(req)
	res.ResponseTime = time.Since(start)
	if err != nil {
		res.Status = StatusError
		res.Error = err.Error()
		return res
	}
	defer resp.Body.Close()
	res.HTTPCode = resp.StatusCode

	// Classify. Success codes take precedence, then failure, then rate-limit.
	switch {
	case containsInt(spec.EffectiveSuccessCodes(), resp.StatusCode):
		res.Status = StatusLive
	case containsInt(spec.EffectiveFailureCodes(), resp.StatusCode):
		res.Status = StatusDead
	case containsInt(spec.EffectiveRateLimitCodes(), resp.StatusCode):
		res.Status = StatusRateLimited
		if ra := resp.Header.Get("Retry-After"); ra != "" {
			if secs, convErr := strconv.Atoi(ra); convErr == nil {
				res.RetryAfter = time.Duration(secs) * time.Second
			}
		}
	default:
		res.Status = StatusUnknown
	}

	// Metadata extraction only for live responses with JSON body and configured paths.
	if res.Status == StatusLive && len(spec.MetadataPaths) > 0 {
		if strings.Contains(resp.Header.Get("Content-Type"), "application/json") {
			bodyBytes, _ := io.ReadAll(io.LimitReader(resp.Body, maxMetadataBody))
			meta := make(map[string]string, len(spec.MetadataPaths))
			for displayName, path := range spec.MetadataPaths {
				if r := gjson.GetBytes(bodyBytes, path); r.Exists() {
					meta[displayName] = r.String()
				}
			}
			if len(meta) > 0 {
				res.Metadata = meta
			}
		}
	}
	return res
}

// VerifyAll runs verification for every finding through an ants worker pool
// of the given size (or DefaultWorkers when workers <= 0). The returned
// channel is closed once every finding has been processed or ctx is cancelled.
//
// Findings whose provider is not present in reg are emitted as
// Result{Status: StatusUnknown, Error: "provider not found in registry"}
// rather than silently dropped.
func (v *HTTPVerifier) VerifyAll(ctx context.Context, findings []engine.Finding, reg *providers.Registry, workers int) <-chan Result {
	if workers <= 0 {
		workers = DefaultWorkers
	}
	out := make(chan Result, len(findings))

	pool, err := ants.NewPool(workers)
	if err != nil {
		go func() {
			defer close(out)
			for _, f := range findings {
				out <- Result{
					ProviderName: f.ProviderName,
					KeyMasked:    f.KeyMasked,
					Status:       StatusError,
					Error:        "pool init: " + err.Error(),
				}
			}
		}()
		return out
	}

	var wg sync.WaitGroup
	go func() {
		defer close(out)
		defer pool.Release()

		for i := range findings {
			if ctx.Err() != nil {
				break
			}
			f := findings[i]
			wg.Add(1)
			submitErr := pool.Submit(func() {
				defer wg.Done()
				prov, ok := reg.Get(f.ProviderName)
				if !ok {
					out <- Result{
						ProviderName: f.ProviderName,
						KeyMasked:    f.KeyMasked,
						Status:       StatusUnknown,
						Error:        "provider not found in registry",
					}
					return
				}
				out <- v.Verify(ctx, f, prov)
			})
			if submitErr != nil {
				wg.Done()
				out <- Result{
					ProviderName: f.ProviderName,
					KeyMasked:    f.KeyMasked,
					Status:       StatusError,
					Error:        submitErr.Error(),
				}
			}
		}
		wg.Wait()
	}()
	return out
}

// substituteKey replaces both {{KEY}} and the legacy {KEY} placeholder.
func substituteKey(s, key string) string {
	s = strings.ReplaceAll(s, "{{KEY}}", key)
	s = strings.ReplaceAll(s, "{KEY}", key)
	return s
}

func containsInt(haystack []int, needle int) bool {
	for _, x := range haystack {
		if x == needle {
			return true
		}
	}
	return false
}