package httpapi

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"io"
	"log"
	"net/http"
	"os"
	"regexp"
	"strings"
	"time"

	"knowledge-governance/internal/governance"
	"knowledge-governance/internal/jobs"
	postgresstore "knowledge-governance/internal/platform/postgres"
)

// DingTalk login proxy. The scan-code login itself lives in the
// dingtalk-login sidecar (headless Chromium); the API is the authenticated
// gate and browser relay, so no QR or token crosses the web origin without a
// session. classifyRole keeps every non-GET at engineer+; capture replacement
// remains a deliberate human action.
//
//	POST   /api/v1/dingtalk-session       -> start a login session {space?}
//	GET    /api/v1/dingtalk-session/{id}  -> poll state (qr_png while waiting)
//	DELETE /api/v1/dingtalk-session/{id}  -> abort a session

func dingtalkSidecarURL() string {
	return strings.TrimRight(strings.TrimSpace(os.Getenv("DINGTALK_LOGIN_SIDECAR_URL")), "/")
}

func requireDingtalkIdentity(w http.ResponseWriter, r *http.Request) bool {
	_, ok := requireSessionIdentity(w, r)
	return ok
}

func startDingtalkSession(w http.ResponseWriter, r *http.Request) {
	if !requireDingtalkIdentity(w, r) {
		return
	}
	var body struct {
		Space string `json:"space"`
	}
	if r.Body != nil && r.ContentLength != 0 {
		if err := decodeJSONStrict(r, &body); err != nil {
			writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid_request_body"})
			return
		}
	}
	payload, _ := json.Marshal(map[string]string{"space": strings.TrimSpace(body.Space)})
	status, data := proxyDingtalk(http.MethodPost, "/sessions", payload)
	log.Printf("dingtalk-login session started by %s (status %d)", actorFor(r), status)
	writeProxyResult(w, status, data)
}

func getDingtalkSession(w http.ResponseWriter, r *http.Request) {
	if !requireDingtalkIdentity(w, r) {
		return
	}
	id := safeSessionID(r.PathValue("id"))
	if id == "" {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid_session_id"})
		return
	}
	status, data := proxyDingtalk(http.MethodGet, "/sessions/"+id, nil)
	writeProxyResult(w, status, data)
}

func deleteDingtalkSession(w http.ResponseWriter, r *http.Request) {
	if !requireDingtalkIdentity(w, r) {
		return
	}
	id := safeSessionID(r.PathValue("id"))
	if id == "" {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid_session_id"})
		return
	}
	status, data := proxyDingtalk(http.MethodDelete, "/sessions/"+id, nil)
	log.Printf("dingtalk-login session %s closed by %s", id, actorFor(r))
	writeProxyResult(w, status, data)
}

// registerDingtalkSpace resolves a DingTalk knowledge-base space URL through
// the login sidecar and, on success, registers the returned space as a
// source connection (deterministic id, enabled, manual-only schedule until an
// admin sets an interval). Re-registering the same space re-syncs name/root.
func registerDingtalkSpace(w http.ResponseWriter, r *http.Request, config Config) {
	if !requireDingtalkIdentity(w, r) {
		return
	}
	operationID, ok := requireOperationID(w, r)
	if !ok {
		return
	}
	var input struct {
		URL string `json:"url"`
	}
	if err := decodeJSONStrict(r, &input); err != nil || strings.TrimSpace(input.URL) == "" {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "url is required"})
		return
	}
	// dws 已经持有有效凭据（access 自动续期、refresh 一个月），登记也该走它：
	// 只有 dws 解析不出这个空间时，才回落到老的扫码侧车。
	if registered, ok := registerSpaceThroughDWS(w, r, config, strings.TrimSpace(input.URL), operationID); ok || registered {
		return
	}
	payload, _ := json.Marshal(map[string]string{"url": strings.TrimSpace(input.URL)})
	status, data := proxyDingtalk(http.MethodPost, "/spaces/add", payload)
	if status != http.StatusOK {
		if status == 0 {
			writeJSON(w, http.StatusServiceUnavailable, map[string]string{"error": "dingtalk_login_unavailable"})
			return
		}
		// Relay the sidecar's error (login_required / space_not_found /
		// name_conflict) verbatim; bodies are machine codes, no secrets.
		writeProxyResult(w, status, data)
		return
	}
	var resolved struct {
		Key  string `json:"key"`
		Name string `json:"name"`
		Root string `json:"root"`
	}
	if err := json.Unmarshal(data, &resolved); err != nil || resolved.Key == "" || resolved.Name == "" || resolved.Root == "" {
		writeJSON(w, http.StatusBadGateway, map[string]string{"error": "invalid sidecar registration response"})
		return
	}
	store, ok := config.Store.(interface {
		RegisterDingtalkSpace(context.Context, postgresstore.RegisterDingtalkSpaceInput) (string, error)
	})
	if !ok {
		writeJSON(w, http.StatusServiceUnavailable, map[string]string{"error": "registration_unavailable"})
		return
	}
	spaceID := extractDingtalkSpaceID(input.URL)
	if spaceID == "" {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid space url"})
		return
	}
	connectionID, err := store.RegisterDingtalkSpace(r.Context(), postgresstore.RegisterDingtalkSpaceInput{
		RootKey: resolved.Key, Name: resolved.Name, SpaceID: spaceID, RootID: resolved.Root, Now: config.Now(), Actor: actorFor(r),
	})
	switch {
	case errors.Is(err, postgresstore.ErrDingtalkSpaceNameTaken):
		writeJSON(w, http.StatusConflict, map[string]string{
			"error": "space_name_conflict",
			"hint":  "已有同名来源仍在使用（未下架）：请先在该来源卡片上「去掉来源」，或确认选的是同一个知识库空间。",
		})
		return
	case errors.Is(err, postgresstore.ErrDingtalkSpaceIdentityConflict):
		writeJSON(w, http.StatusConflict, map[string]string{
			"error": "space_identity_conflict",
			"hint":  "这个登记键已指向另一个知识库空间：请刷新列表后重试；若仍失败，把该来源「去掉来源」后再登记。",
		})
		return
	case err != nil:
		// 真正的数据库/内部故障不能伪装成"冲突"：换个 500 才有人去查日志。
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "space_registration_failed"})
		return
	}
	// First scan is enqueued right away: the new connection has no catalog
	// head yet, so the generic sources/{id}/refresh endpoint would 404 until
	// the first snapshot exists.
	if enqueuer, ok := config.Store.(interface {
		EnqueueCatalogRefreshWithOperation(context.Context, governance.CatalogSource, string, time.Time) (jobs.Job, bool, error)
	}); ok {
		if _, _, enqueueErr := enqueuer.EnqueueCatalogRefreshWithOperation(r.Context(), governance.CatalogSource{
			ConnectionID: connectionID, SourceType: governance.SourceTypeDingTalk, Name: resolved.Name,
		}, operationID+":first", config.Now().UTC()); enqueueErr != nil {
			log.Printf("dingtalk space %s registered but first refresh enqueue failed: %v", connectionID, enqueueErr)
		}
	}
	log.Printf("dingtalk space %q registered as connection %s by %s", resolved.Name, connectionID, actorFor(r))
	writeJSON(w, http.StatusCreated, map[string]any{"data": map[string]string{
		"connection_id": connectionID, "name": resolved.Name,
	}})
}

var dingtalkSpacePattern = regexp.MustCompile(`/spaces/([A-Za-z0-9_-]+)`)

func extractDingtalkSpaceID(raw string) string {
	match := dingtalkSpacePattern.FindStringSubmatch(raw)
	if len(match) == 2 {
		return match[1]
	}
	trimmed := strings.TrimSpace(raw)
	if regexp.MustCompile(`^[A-Za-z0-9_-]{8,64}$`).MatchString(trimmed) {
		return trimmed
	}
	return ""
}

func safeSessionID(id string) string {
	id = strings.TrimSpace(id)
	if id == "" || len(id) > 64 {
		return ""
	}
	for _, c := range id {
		if !(c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c >= '0' && c <= '9' || c == '-') {
			return ""
		}
	}
	return id
}

func writeProxyResult(w http.ResponseWriter, status int, data []byte) {
	if status == 0 || data == nil {
		writeJSON(w, http.StatusServiceUnavailable, map[string]string{"error": "dingtalk_login_unavailable"})
		return
	}
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_, _ = w.Write(data)
}

func proxyDingtalk(method, path string, body []byte) (int, []byte) {
	base := dingtalkSidecarURL()
	if base == "" {
		return 0, nil
	}
	var reader io.Reader
	if body != nil {
		reader = bytes.NewReader(body)
	}
	req, err := http.NewRequest(method, base+path, reader)
	if err != nil {
		return 0, nil
	}
	if body != nil {
		req.Header.Set("Content-Type", "application/json")
	}
	client := &http.Client{Timeout: 15 * time.Second}
	resp, err := client.Do(req)
	if err != nil {
		return 0, nil
	}
	defer resp.Body.Close()
	data, err := io.ReadAll(io.LimitReader(resp.Body, 4<<20))
	if err != nil {
		return resp.StatusCode, nil
	}
	return resp.StatusCode, data
}

// resolveSpaceViaDWS 用 dws 列举结果定位一个空间：返回确定性登记键、名称与根节点。
// 认不出就 ok=false，调用方回落到老的扫码侧车（历史空间仍能被登记）。
func resolveSpaceViaDWS(ctx context.Context, lister dingtalkSourcesLister, rawURL string) (rootKey, name, rootID, spaceID string, ok bool) {
	spaceID = extractDingtalkSpaceID(rawURL)
	if lister == nil || spaceID == "" {
		return "", "", "", "", false
	}
	discovered, err := lister.ListAvailableDingtalkSources(ctx)
	if err != nil {
		return "", "", "", "", false
	}
	for _, base := range discovered.KnowledgeBases {
		if base.SpaceID == spaceID {
			// 知识库：URL 里的 id 就是空间 id，抓取侧按 spaces/<id> 匹配。
			return "space-" + spaceID, base.Name, spaceID, spaceID, true
		}
	}
	for _, space := range discovered.DriveSpaces {
		if space.SpaceID == spaceID && space.RootFolderID != "" {
			return "space-" + spaceID, space.Name, space.RootFolderID, spaceID, true
		}
	}
	return "", "", "", "", false
}

// registerSpaceThroughDWS 用 dws 凭据直接登记来源，不再要求扫码会话。
func registerSpaceThroughDWS(w http.ResponseWriter, r *http.Request, config Config, rawURL, operationID string) (bool, bool) {
	ctx, cancel := context.WithTimeout(r.Context(), 30*time.Second)
	defer cancel()
	rootKey, name, rootID, spaceID, ok := resolveSpaceViaDWS(ctx, config.DingtalkSources, rawURL)
	if !ok {
		return false, false
	}
	store, wired := config.Store.(interface {
		RegisterDingtalkSpace(context.Context, postgresstore.RegisterDingtalkSpaceInput) (string, error)
	})
	if !wired {
		writeJSON(w, http.StatusServiceUnavailable, map[string]string{"error": "registration_unavailable"})
		return true, false
	}
	connectionID, err := store.RegisterDingtalkSpace(ctx, postgresstore.RegisterDingtalkSpaceInput{
		RootKey: rootKey, Name: name, SpaceID: spaceID, RootID: rootID, Now: config.Now(), Actor: actorFor(r),
	})
	switch {
	case errors.Is(err, postgresstore.ErrDingtalkSpaceNameTaken):
		writeJSON(w, http.StatusConflict, map[string]string{"error": "space_name_conflict", "hint": "已有同名来源，但空间标识不一致；请核对已有来源，不能按名称判定添加成功。"})
		return true, false
	case errors.Is(err, postgresstore.ErrDingtalkSpaceIdentityConflict):
		writeJSON(w, http.StatusConflict, map[string]string{
			"error": "space_identity_conflict",
			"hint":  "这个登记键已指向另一个知识库空间：请刷新列表后重试。",
		})
		return true, false
	case err != nil:
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "space_registration_failed"})
		return true, false
	}
	if enqueuer, wired := config.Store.(interface {
		EnqueueCatalogRefreshWithOperation(context.Context, governance.CatalogSource, string, time.Time) (jobs.Job, bool, error)
	}); wired {
		if _, _, enqueueErr := enqueuer.EnqueueCatalogRefreshWithOperation(ctx, governance.CatalogSource{
			ConnectionID: connectionID, SourceType: governance.SourceTypeDingTalk, Name: name,
		}, operationID+":first", config.Now().UTC()); enqueueErr != nil {
			log.Printf("dingtalk space %s registered but first refresh enqueue failed: %v", connectionID, enqueueErr)
		}
	}
	log.Printf("dingtalk space %q registered as connection %s by %s (dws)", name, connectionID, actorFor(r))
	writeJSON(w, http.StatusCreated, map[string]any{"data": map[string]string{
		"connection_id": connectionID, "name": name,
	}})
	return true, true
}