// GoBD retention-rule ("Aufbewahrungsregeln") HTTP handlers (see
// internal/storage/retention_rules.go):
//
//	GET    /api/retention-rules            list all rules of the tenant
//	POST   /api/retention-rules            create a rule
//	PATCH  /api/retention-rules/{id}        update a rule
//	DELETE /api/retention-rules/{id}        delete a rule
//	GET    /api/retention-rules/eligible    documents eligible for disposition
//	GET    /api/retention-rules/preview     dry-run of ApplyRetentionRules (no write)
//
// Rules are compliance-critical (they define how long documents must be kept),
// so create/update/delete require domain_admin (s.authAdmin). Reading (list,
// eligible, preview) is a normal tenant action (s.auth). Ownership is enforced
// in the store layer (id+tenant_id). Every mutation is audit-logged, including
// failures.
package api

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

	"archivdms/internal/audit"
	"archivdms/internal/storage"
)

// retentionRuleRequest is the JSON body for create/update. Pointers where the
// store field is a pointer, so "not set" round-trips correctly.
type retentionRuleRequest struct {
	DocTypeID                  *int64  `json:"doc_type_id"`
	Name                       string  `json:"name"`
	TriggerType                string  `json:"trigger_type"`
	TriggerReference           string  `json:"trigger_reference"`
	RetentionYears             *int    `json:"retention_years"`
	RetentionDays              *int    `json:"retention_days"`
	LegalBasis                 string  `json:"legal_basis"`
	RequiresApprovalForDestroy *bool   `json:"requires_approval_for_destroy"`
	DSGVOConflict              *bool   `json:"dsgvo_conflict"`
	Active                     *bool   `json:"active"`
}

// toRule maps the request onto a storage.RetentionRule. requires_approval and
// active default to true when omitted (safe GoBD default: keep approval on).
func (req retentionRuleRequest) toRule() storage.RetentionRule {
	requiresApproval := true
	if req.RequiresApprovalForDestroy != nil {
		requiresApproval = *req.RequiresApprovalForDestroy
	}
	active := true
	if req.Active != nil {
		active = *req.Active
	}
	dsgvo := false
	if req.DSGVOConflict != nil {
		dsgvo = *req.DSGVOConflict
	}
	return storage.RetentionRule{
		DocTypeID:                  req.DocTypeID,
		Name:                       req.Name,
		TriggerType:                req.TriggerType,
		TriggerReference:           req.TriggerReference,
		RetentionYears:             req.RetentionYears,
		RetentionDays:              req.RetentionDays,
		LegalBasis:                 req.LegalBasis,
		RequiresApprovalForDestroy: requiresApproval,
		DSGVOConflict:              dsgvo,
		Active:                     active,
	}
}

// handleListRetentionRules handles GET /api/retention-rules.
func (s *Server) handleListRetentionRules(w http.ResponseWriter, r *http.Request) {
	sess := sessionFromCtx(r.Context())
	if sess.TenantID == nil {
		writeError(w, http.StatusForbidden, "tenant context required")
		return
	}
	rules, err := s.store.ListRetentionRules(r.Context(), *sess.TenantID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "list retention rules failed")
		return
	}
	writeJSON(w, http.StatusOK, rules)
}

// handleCreateRetentionRule handles POST /api/retention-rules (domain_admin+).
func (s *Server) handleCreateRetentionRule(w http.ResponseWriter, r *http.Request) {
	sess := sessionFromCtx(r.Context())
	if sess.TenantID == nil {
		writeError(w, http.StatusForbidden, "tenant context required")
		return
	}
	var req retentionRuleRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}
	rule := req.toRule()
	rule.CreatedBy = &sess.UserID

	created, err := s.store.CreateRetentionRule(r.Context(), *sess.TenantID, rule)
	if err != nil {
		s.audlog.Log(audit.Entry{
			EventType: audit.EventRetentionRuleCreate, Username: sess.Username, TenantID: sess.TenantID,
			Success: false, Detail: "retention_rule_create err:" + err.Error(),
		})
		writeError(w, retentionRuleErrStatus(err), retentionRuleErrMsg(err, "create retention rule failed"))
		return
	}
	s.audlog.Log(audit.Entry{
		EventType: audit.EventRetentionRuleCreate, Username: sess.Username, TenantID: sess.TenantID,
		Success: true, Detail: "retention_rule_create id:" + strconv.FormatInt(created.ID, 10) + " name:" + created.Name,
	})
	writeJSON(w, http.StatusCreated, created)
}

// handleUpdateRetentionRule handles PATCH /api/retention-rules/{id} (domain_admin+).
func (s *Server) handleUpdateRetentionRule(w http.ResponseWriter, r *http.Request) {
	sess := sessionFromCtx(r.Context())
	if sess.TenantID == nil {
		writeError(w, http.StatusForbidden, "tenant context required")
		return
	}
	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid id")
		return
	}
	var req retentionRuleRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}
	updated, err := s.store.UpdateRetentionRule(r.Context(), id, *sess.TenantID, req.toRule())
	if err != nil {
		s.audlog.Log(audit.Entry{
			EventType: audit.EventRetentionRuleUpdate, Username: sess.Username, TenantID: sess.TenantID,
			Success: false, Detail: "retention_rule_update id:" + strconv.FormatInt(id, 10) + " err:" + err.Error(),
		})
		writeError(w, retentionRuleErrStatus(err), retentionRuleErrMsg(err, "update retention rule failed"))
		return
	}
	s.audlog.Log(audit.Entry{
		EventType: audit.EventRetentionRuleUpdate, Username: sess.Username, TenantID: sess.TenantID,
		Success: true, Detail: "retention_rule_update id:" + strconv.FormatInt(id, 10),
	})
	writeJSON(w, http.StatusOK, updated)
}

// handleDeleteRetentionRule handles DELETE /api/retention-rules/{id} (domain_admin+).
func (s *Server) handleDeleteRetentionRule(w http.ResponseWriter, r *http.Request) {
	sess := sessionFromCtx(r.Context())
	if sess.TenantID == nil {
		writeError(w, http.StatusForbidden, "tenant context required")
		return
	}
	id, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid id")
		return
	}
	if err := s.store.DeleteRetentionRule(r.Context(), id, *sess.TenantID); err != nil {
		s.audlog.Log(audit.Entry{
			EventType: audit.EventRetentionRuleDelete, Username: sess.Username, TenantID: sess.TenantID,
			Success: false, Detail: "retention_rule_delete id:" + strconv.FormatInt(id, 10) + " err:" + err.Error(),
		})
		writeError(w, retentionRuleErrStatus(err), retentionRuleErrMsg(err, "delete retention rule failed"))
		return
	}
	s.audlog.Log(audit.Entry{
		EventType: audit.EventRetentionRuleDelete, Username: sess.Username, TenantID: sess.TenantID,
		Success: true, Detail: "retention_rule_delete id:" + strconv.FormatInt(id, 10),
	})
	writeJSON(w, http.StatusOK, map[string]string{"status": "deleted"})
}

// handleListEligibleForDisposition handles GET /api/retention-rules/eligible:
// documents whose retention has expired but which are not yet in the trash.
func (s *Server) handleListEligibleForDisposition(w http.ResponseWriter, r *http.Request) {
	sess := sessionFromCtx(r.Context())
	if sess.TenantID == nil {
		writeError(w, http.StatusForbidden, "tenant context required")
		return
	}
	docs, err := s.store.ListEligibleForDisposition(r.Context(), *sess.TenantID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "list eligible-for-disposition documents failed")
		return
	}
	writeJSON(w, http.StatusOK, docs)
}

// handlePreviewRetentionRules handles GET /api/retention-rules/preview: a
// dry-run of ApplyRetentionRules for the current tenant. No writes.
func (s *Server) handlePreviewRetentionRules(w http.ResponseWriter, r *http.Request) {
	sess := sessionFromCtx(r.Context())
	if sess.TenantID == nil {
		writeError(w, http.StatusForbidden, "tenant context required")
		return
	}
	preview, err := s.store.PreviewRetentionRules(r.Context(), *sess.TenantID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "preview retention rules failed")
		return
	}
	if preview == nil {
		preview = []storage.RetentionPreview{}
	}
	writeJSON(w, http.StatusOK, preview)
}

// retentionRuleErrStatus maps store errors to HTTP status codes. Validation
// errors (bad trigger_type, missing retention period, bad fixed_date) surface as
// 400; not-found as 404; everything else 500.
func retentionRuleErrStatus(err error) int {
	if errors.Is(err, storage.ErrRetentionRuleNotFound) {
		return http.StatusNotFound
	}
	if isRetentionValidationErr(err) {
		return http.StatusBadRequest
	}
	return http.StatusInternalServerError
}

// retentionRuleErrMsg returns the validation message verbatim (safe, no PII) so
// the frontend can show it, or a generic fallback otherwise.
func retentionRuleErrMsg(err error, fallback string) string {
	if errors.Is(err, storage.ErrRetentionRuleNotFound) {
		return "retention rule not found"
	}
	if isRetentionValidationErr(err) {
		return err.Error()
	}
	return fallback
}

// isRetentionValidationErr reports whether err is a validateRetentionRule
// cross-field error (all prefixed "retention rule:" in the store).
func isRetentionValidationErr(err error) bool {
	if err == nil || errors.Is(err, storage.ErrRetentionRuleNotFound) {
		return false
	}
	msg := err.Error()
	const prefix = "retention rule: "
	return len(msg) >= len(prefix) && msg[:len(prefix)] == prefix
}