package api

import (
	"encoding/json"
	"net/http"
	"strconv"
	"strings"

	"archivdms/internal/audit"
	"archivdms/internal/dateformat"
	"archivdms/internal/storage"
	"archivdms/internal/userstore"
)

// resolveTenantSettingsTenant determines which tenant the request targets,
// mirroring resolveLDAPTenant: domain_admin is pinned to its own signed
// session tenant (IDOR-safe, query params ignored); superadmin (no session
// tenant) must pass ?tenant_id=. Returns the tenant ID and false when the
// request is not authorised or the tenant cannot be determined (the caller
// has already written the response).
func (s *Server) resolveTenantSettingsTenant(w http.ResponseWriter, r *http.Request) (int64, bool) {
	sess := sessionFromCtx(r.Context())

	if sess.Role == userstore.RoleSuperAdmin {
		q := r.URL.Query().Get("tenant_id")
		if q == "" {
			writeError(w, http.StatusBadRequest, "tenant_id query parameter required for superadmin")
			return 0, false
		}
		tid, err := strconv.ParseInt(q, 10, 64)
		if err != nil || tid <= 0 {
			writeError(w, http.StatusBadRequest, "invalid tenant_id")
			return 0, false
		}
		return tid, true
	}

	if sess.TenantID == nil {
		writeError(w, http.StatusForbidden, "no tenant context")
		return 0, false
	}
	return *sess.TenantID, true
}

// availableScanTitleFormats returns the example token patterns the frontend can
// offer as clickable starting points. These are suggestions only — any free
// token pattern is accepted (see dateformat.Translate) — not a validation
// constraint. Returned as a fresh slice so callers never share backing storage.
func availableScanTitleFormats() []string {
	out := make([]string, len(exampleScanTitleFormats))
	copy(out, exampleScanTitleFormats)
	return out
}

type tenantSettingsResponse struct {
	ScanTitleDateFormat string `json:"scan_title_date_format"`
	ScanTitlePrefix     string `json:"scan_title_prefix"`
	// DefaultTitleTemplate is the tenant-wide fallback title template (Go
	// text/template) used when an applied classification template carries no
	// own title_template. Empty string means "no tenant default".
	DefaultTitleTemplate string `json:"default_title_template"`
	// AvailableFormats is a list of example patterns (suggestions), not an
	// allow-list; the field name is kept for frontend compatibility.
	AvailableFormats []string `json:"available_formats"`
}

// effectiveScanTitlePrefix returns the tenant's stored prefix, or the default
// for empty/legacy rows, so the response always reflects what would actually be
// used at upload time.
func effectiveScanTitlePrefix(stored string) string {
	if p := strings.TrimSpace(stored); p != "" {
		return p
	}
	return defaultScanTitlePrefix
}

// effectiveScanTitleFormat returns the tenant's stored token pattern, or the
// default for empty/invalid rows, so the response always reflects the pattern
// that would actually be used at upload time.
func effectiveScanTitleFormat(stored string) string {
	if s := strings.TrimSpace(stored); s != "" {
		if _, err := dateformat.Translate(s); err == nil {
			return s
		}
	}
	return defaultScanTitleDateFormat
}

// handleGetTenantSettings returns the tenant's own settings (currently the
// placeholder-title date format) plus a list of example format patterns
// (suggestions for the frontend, not an allow-list).
func (s *Server) handleGetTenantSettings(w http.ResponseWriter, r *http.Request) {
	if s.tenantStore == nil {
		writeError(w, http.StatusServiceUnavailable, "tenant store not configured")
		return
	}
	tenantID, ok := s.resolveTenantSettingsTenant(w, r)
	if !ok {
		return
	}

	t, err := s.tenantStore.GetByID(r.Context(), tenantID)
	if err != nil || t == nil {
		writeError(w, http.StatusInternalServerError, "load tenant settings failed")
		return
	}

	writeJSON(w, http.StatusOK, tenantSettingsResponse{
		ScanTitleDateFormat:  effectiveScanTitleFormat(t.ScanTitleDateFormat),
		ScanTitlePrefix:      effectiveScanTitlePrefix(t.ScanTitlePrefix),
		DefaultTitleTemplate: t.DefaultTitleTemplate,
		AvailableFormats:     availableScanTitleFormats(),
	})
}

// updateTenantSettingsRequest uses pointer fields for PATCH-like semantics:
// only the fields present in the JSON body are updated, so the two settings
// can be changed independently of one another.
type updateTenantSettingsRequest struct {
	ScanTitleDateFormat  *string `json:"scan_title_date_format"`
	ScanTitlePrefix      *string `json:"scan_title_prefix"`
	DefaultTitleTemplate *string `json:"default_title_template"`
}

// handleUpdateTenantSettings persists the tenant's placeholder-title date
// format. The submitted value is a free token pattern (e.g. "DD.MM.YYYY HH:mm")
// validated via dateformat.Translate; an unparseable pattern yields 400 with
// the translator's error message. Every attempt — success or failure — is
// audit-logged (GoBD).
func (s *Server) handleUpdateTenantSettings(w http.ResponseWriter, r *http.Request) {
	sess := sessionFromCtx(r.Context())

	if s.tenantStore == nil {
		writeError(w, http.StatusServiceUnavailable, "tenant store not configured")
		return
	}
	tenantID, ok := s.resolveTenantSettingsTenant(w, r)
	if !ok {
		return
	}

	logFail := func(detail string) {
		tid := tenantID
		s.audlog.Log(audit.Entry{
			EventType: audit.EventTenantMgmt, Username: sess.Username,
			TenantID: &tid, Success: false, Detail: detail,
		})
	}

	var req updateTenantSettingsRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		logFail("tenant_settings invalid_body")
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}
	if req.ScanTitleDateFormat == nil && req.ScanTitlePrefix == nil && req.DefaultTitleTemplate == nil {
		logFail("tenant_settings no_fields")
		writeError(w, http.StatusBadRequest, "no settings provided")
		return
	}

	// Validate everything before persisting anything, so a bad prefix can never
	// leave a half-applied update.
	if req.ScanTitleDateFormat != nil {
		if _, err := dateformat.Translate(*req.ScanTitleDateFormat); err != nil {
			logFail("tenant_settings invalid_scan_title_date_format:" + *req.ScanTitleDateFormat)
			writeError(w, http.StatusBadRequest, err.Error())
			return
		}
	}
	if req.ScanTitlePrefix != nil && strings.TrimSpace(*req.ScanTitlePrefix) == "" {
		logFail("tenant_settings empty_scan_title_prefix")
		writeError(w, http.StatusBadRequest, "scan_title_prefix must not be empty")
		return
	}
	// An empty default_title_template is allowed (clears the tenant default);
	// a non-empty one must parse as a valid Go text/template.
	if req.DefaultTitleTemplate != nil {
		if err := storage.ValidateTitleTemplate(*req.DefaultTitleTemplate); err != nil {
			logFail("tenant_settings invalid_default_title_template")
			writeError(w, http.StatusBadRequest, err.Error())
			return
		}
	}

	var detail string
	if req.ScanTitleDateFormat != nil {
		if err := s.tenantStore.UpdateScanTitleDateFormat(r.Context(), tenantID, *req.ScanTitleDateFormat); err != nil {
			logFail("tenant_settings update_failed")
			writeError(w, http.StatusInternalServerError, "save tenant settings failed")
			return
		}
		detail += " scan_title_date_format:" + *req.ScanTitleDateFormat
	}
	if req.ScanTitlePrefix != nil {
		if err := s.tenantStore.UpdateScanTitlePrefix(r.Context(), tenantID, *req.ScanTitlePrefix); err != nil {
			// Store-level validation (length) or DB error.
			logFail("tenant_settings update_failed")
			writeError(w, http.StatusBadRequest, "invalid scan_title_prefix")
			return
		}
		detail += " scan_title_prefix:" + strings.TrimSpace(*req.ScanTitlePrefix)
	}
	if req.DefaultTitleTemplate != nil {
		if err := s.tenantStore.UpdateDefaultTitleTemplate(r.Context(), tenantID, *req.DefaultTitleTemplate); err != nil {
			logFail("tenant_settings update_failed")
			writeError(w, http.StatusBadRequest, "invalid default_title_template")
			return
		}
		detail += " default_title_template:" + strings.TrimSpace(*req.DefaultTitleTemplate)
	}

	tid := tenantID
	s.audlog.Log(audit.Entry{
		EventType: audit.EventTenantMgmt, Username: sess.Username,
		TenantID: &tid, Success: true,
		Detail: "tenant_settings" + detail,
	})

	// Reload so the response reflects the effective persisted state for both
	// fields, regardless of which one this request changed.
	t, err := s.tenantStore.GetByID(r.Context(), tenantID)
	if err != nil || t == nil {
		writeError(w, http.StatusInternalServerError, "load tenant settings failed")
		return
	}
	writeJSON(w, http.StatusOK, tenantSettingsResponse{
		ScanTitleDateFormat:  effectiveScanTitleFormat(t.ScanTitleDateFormat),
		ScanTitlePrefix:      effectiveScanTitlePrefix(t.ScanTitlePrefix),
		DefaultTitleTemplate: t.DefaultTitleTemplate,
		AvailableFormats:     availableScanTitleFormats(),
	})
}