package cabana

import (
	"context"
	"errors"
	"net/http"
	"reflect"
	"regexp"
	"strconv"
	"strings"

	"git.golem15.com/golem15/summercms/modules/bouncer"
	"git.golem15.com/golem15/summercms/modules/lagoon"
	"git.golem15.com/golem15/summercms/modules/lagoon/attach"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

// SessionKeyHeader carries the admin SPA's form session key (D-02): a
// random key the SPA generates when a form opens and sends with every file
// upload, file removal and the final save. Work bound to the key is applied
// by the record's next create or update save, inside its transaction.
const SessionKeyHeader = "X-Session-Key"

// ChildSessionKeyHeader carries the session key of a relation child form
// (D-17): the child modal's own form key, sent with the child's file calls
// and with its create or update, which applies the child's file bindings.
// A child modal on a record that is not saved yet carries both headers.
const ChildSessionKeyHeader = "X-Child-Session-Key"

// sessionKeyPattern is the accepted key shape: 32 to 128 URL-safe
// characters, at least 128 bits for a base64url key.
var sessionKeyPattern = regexp.MustCompile(`^[A-Za-z0-9_-]{32,128}$`)

// sessionKeyFrom reads the X-Session-Key header. An absent or empty header
// is ("", false, nil); a malformed key is a validation error on session_key.
func sessionKeyFrom(r *http.Request) (string, bool, error) {
	raw := strings.TrimSpace(r.Header.Get(SessionKeyHeader))
	if raw == "" {
		return "", false, nil
	}
	if !sessionKeyPattern.MatchString(raw) {
		return "", false, &ValidationError{Details: map[string]any{"session_key": []string{"The session key is invalid."}}}
	}
	return raw, true, nil
}

// childSessionKeyFrom reads the X-Child-Session-Key header like
// sessionKeyFrom; a malformed key is a validation error on
// child_session_key.
func childSessionKeyFrom(r *http.Request) (string, bool, error) {
	raw := strings.TrimSpace(r.Header.Get(ChildSessionKeyHeader))
	if raw == "" {
		return "", false, nil
	}
	if !sessionKeyPattern.MatchString(raw) {
		return "", false, &ValidationError{Details: map[string]any{"child_session_key": []string{"The child session key is invalid."}}}
	}
	return raw, true, nil
}

// commitDeferred applies the file and relation bindings of in.SessionKey to
// the saved target inside the save transaction (D-04), then rechecks the
// file limits.
//
// It reads every binding of the key, the authenticated admin and the
// controller's morph type whose master_field is a fileupload field or a
// deferrable relation-manager relation allowed in op, locked FOR UPDATE so
// two saves with one key serialize, and applies them in id order. A file
// bind attaches its pending upload (on an attachOne field after deleting
// the file it replaces), a file unbind deletes the attached file; blobs of
// deleted files are removed after commit. A relation bind attaches the
// related record (applyRelationBinding), a relation unbind detaches it. The
// applied rows are deleted; bindings of other fields stay for the purge.
// Then every fileupload field allowed in op must hold at most maxFiles files
// and, when required, at least one. Any failure (a 422 on a file field, or
// on a relation-manager field for an ineligible link) rolls the transaction
// back and leaves the bindings in place.
func (s CRUDService) commitDeferred(ctx context.Context, tx *gorm.DB, cc *CompiledController, target any, op string, in RecordInput) error {
	if cc == nil || cc.Form == nil {
		return nil
	}
	var fields []*compiledFile
	for _, field := range cc.Form.Fields {
		if cf := cc.files[field.Name]; cf != nil && contextAllows(cc, cf.name, op) {
			fields = append(fields, cf)
		}
	}
	relations := map[string]*CompiledRelation{}
	for name, cr := range cc.Relations {
		if cr != nil && cr.deferrable && contextAllows(cc, cr.fieldName, op) {
			relations[name] = cr
		}
	}
	ownerID := primaryText(target)
	if (len(fields) == 0 && len(relations) == 0) || ownerID == "" {
		return nil
	}
	morph, err := lagoon.MorphType(tx, target)
	if err != nil {
		return lifecycleFailure(cc, err)
	}
	principal, _ := bouncer.User(ctx)
	if in.SessionKey != "" && principal != nil && principal.Backend && principal.ID != 0 {
		names := make([]string, 0, len(fields)+len(relations))
		for _, cf := range fields {
			names = append(names, cf.name)
		}
		for name := range relations {
			names = append(names, name)
		}
		key := lagoon.DeferredKey{SessionKey: in.SessionKey, AdminID: principal.ID, MasterType: morph}
		rows, err := lagoon.DeferredBindings(ctx, tx, key, names)
		if err != nil {
			return lifecycleFailure(cc, err)
		}
		rel := RelationService{DB: s.DB, bucket: s.bucket, tr: s.tr}
		parent := &relationParent{model: target, id: pkUint(target)}
		applied := make([]uint, 0, len(rows))
		for _, row := range rows {
			if cf := cc.files[row.MasterField]; cf != nil && row.SlaveType == lagoon.DeferredFileType {
				if row.IsBind {
					err = s.applyFileBind(ctx, tx, cf, morph, ownerID, row)
				} else {
					err = s.applyFileUnbind(ctx, tx, cf, morph, ownerID, row)
				}
				if err != nil {
					return lifecycleFailure(cc, err)
				}
				applied = append(applied, row.ID)
				continue
			}
			cr := relations[row.MasterField]
			if cr == nil {
				continue
			}
			done, err := rel.applyRelationBinding(ctx, tx, cc, cr, parent, row)
			if err != nil {
				return lifecycleFailure(cc, err)
			}
			if done {
				applied = append(applied, row.ID)
			}
		}
		if err := lagoon.DeferredForget(ctx, tx, applied); err != nil {
			return lifecycleFailure(cc, err)
		}
	}
	details := map[string]any{}
	for _, cf := range fields {
		if !cf.required && (!cf.relation.Many || cf.maxFiles == 0) {
			continue
		}
		var n int64
		err := tx.Session(&gorm.Session{NewDB: true, Context: ctx}).Model(&attach.File{}).
			Where("attachment_type = ? AND attachment_id = ? AND field = ?", morph, ownerID, cf.name).
			Count(&n).Error
		if err != nil {
			return lifecycleFailure(cc, err)
		}
		switch {
		case cf.required && n == 0:
			details[cf.name] = []string{fieldMessage(ctx, s.tr, "required", cf.name, nil)}
		case cf.relation.Many && cf.maxFiles > 0 && n > int64(cf.maxFiles):
			details[cf.name] = []string{fieldMessage(ctx, s.tr, "max.array", cf.name, map[string]string{"max": strconv.Itoa(cf.maxFiles)})}
		}
	}
	if len(details) > 0 {
		return &ValidationError{Details: details}
	}
	return nil
}

// applyRelationBinding applies one relation binding of a form session to
// the saved parent (D-04) and reports whether the row was consumed. A
// binding of another slave type is left alone. A bind of a child the
// session created attaches it directly: a hasMany child whose ForeignKey is
// still NULL gets the parent's key through its model (a child gone or owned
// elsewhere is skipped); a belongsToMany record gets its pivot row with the
// envelope's pivot values and RelationBeforeLink stamps. A bind of an
// existing record runs the shared link path with the saved parent, so the
// eligibility checks (RelationExtendManageQuery, ExcludedRelatedIDs, not
// linked yet) run again; an ineligible record fails the save with a 422 on
// the relation-manager field. An unbind runs the shared unlink path.
func (s RelationService) applyRelationBinding(ctx context.Context, tx *gorm.DB, cc *CompiledController, cr *CompiledRelation, parent *relationParent, row lagoon.DeferredBinding) (bool, error) {
	morph, err := lagoon.MorphType(tx, cr.Contract.NewRelated())
	if err != nil {
		return false, err
	}
	if row.SlaveType != morph {
		return false, nil
	}
	n, err := strconv.ParseUint(row.SlaveID, 10, 64)
	if err != nil || n == 0 {
		return true, nil
	}
	id := uint(n)
	if !row.IsBind {
		_, err := s.unlinkRelated(ctx, tx, cc, cr, parent.model, []uint{id})
		return true, err
	}
	env, err := row.Envelope()
	if err != nil {
		return false, err
	}
	var pivot map[string]any
	if len(env.Pivot) > 0 && cr.pivot != nil {
		pivot = env.Pivot
	}
	if !env.Created {
		_, err := s.linkRelated(ctx, tx, cc, cr, parent.model, []uint{id}, pivot, relationInvalid(cr.fieldName, "contains an ineligible record"))
		return true, err
	}
	child := cr.Contract.NewRelated()
	err = tx.Session(&gorm.Session{NewDB: true, Context: ctx}).Clauses(clause.Locking{Strength: "UPDATE"}).
		Where(clause.Eq{Column: clause.Column{Name: primaryColumn(child)}, Value: castPK(child, id)}).Take(child).Error
	if errors.Is(err, gorm.ErrRecordNotFound) {
		return true, nil
	}
	if err != nil {
		return false, err
	}
	if cr.hasMany() {
		if fk, ok := structFieldValue(child, cr.Contract.ForeignKey); !ok || !fk.IsNil() {
			return true, nil
		}
		if err := setModelColumn(child, cr.Contract.ForeignKey, parent.id); err != nil {
			return false, err
		}
		return true, tx.WithContext(ctx).Save(child).Error
	}
	linked, err := pendingRelationIDs(tx, cr, parent.id, []uint{id})
	if err != nil || len(linked) == 0 {
		return true, err
	}
	var pivotRow any
	if pivot != nil {
		pivotRow = cr.Contract.NewPivot()
		if err := s.fillPivot(ctx, tx, cr, pivotRow, pivot); err != nil {
			return false, err
		}
	}
	return true, insertPivot(ctx, tx, cc, cr, parent.model, child, pivotRow)
}

// structFieldValue is the value of a pointer field stored in column, false
// when the column is not a pointer field.
func structFieldValue(model any, column string) (reflect.Value, bool) {
	v := reflect.ValueOf(model)
	for v.Kind() == reflect.Pointer {
		if v.IsNil() {
			return reflect.Value{}, false
		}
		v = v.Elem()
	}
	f := fieldByColumn(v, column)
	if !f.IsValid() || f.Kind() != reflect.Pointer {
		return reflect.Value{}, false
	}
	return f, true
}

// applyFileBind attaches a pending upload to the owner. A row that is gone
// or already attached somewhere is ignored. On an attachOne field the file
// it replaces is deleted first (WinterCMS's AttachOne::add).
func (s CRUDService) applyFileBind(ctx context.Context, tx *gorm.DB, cf *compiledFile, morph, ownerID string, row lagoon.DeferredBinding) error {
	id, err := strconv.ParseUint(row.SlaveID, 10, 64)
	if err != nil || id == 0 {
		return nil
	}
	f, err := lockFile(ctx, tx, uint(id))
	if err != nil || f == nil || f.AttachmentID != "" || f.AttachmentType != "" {
		return err
	}
	q := tx.Session(&gorm.Session{NewDB: true, Context: ctx})
	if !cf.relation.Many {
		var previous []attach.File
		err := q.Clauses(clause.Locking{Strength: "UPDATE"}).
			Where("attachment_type = ? AND attachment_id = ? AND field = ? AND id <> ?", morph, ownerID, cf.name, f.ID).
			Find(&previous).Error
		if err != nil {
			return err
		}
		for _, old := range previous {
			if err := s.deleteFile(ctx, tx, old); err != nil {
				return err
			}
		}
	}
	return q.Model(&attach.File{}).
		Where("id = ?", f.ID).
		Updates(map[string]any{"attachment_type": morph, "attachment_id": ownerID, "field": cf.name}).Error
}

// applyFileUnbind deletes a file attached to this owner and field; a file
// that is not attached there is ignored.
func (s CRUDService) applyFileUnbind(ctx context.Context, tx *gorm.DB, cf *compiledFile, morph, ownerID string, row lagoon.DeferredBinding) error {
	id, err := strconv.ParseUint(row.SlaveID, 10, 64)
	if err != nil || id == 0 {
		return nil
	}
	var f attach.File
	err = tx.Session(&gorm.Session{NewDB: true, Context: ctx}).
		Clauses(clause.Locking{Strength: "UPDATE"}).
		Where("id = ? AND attachment_type = ? AND attachment_id = ? AND field = ?", id, morph, ownerID, cf.name).
		Take(&f).Error
	if errors.Is(err, gorm.ErrRecordNotFound) {
		return nil
	}
	if err != nil {
		return err
	}
	return s.deleteFile(ctx, tx, f)
}

// deleteFile deletes a file row now and its blobs after commit.
func (s CRUDService) deleteFile(ctx context.Context, tx *gorm.DB, f attach.File) error {
	if err := tx.Session(&gorm.Session{NewDB: true, Context: ctx}).Where("id = ?", f.ID).Delete(&attach.File{}).Error; err != nil {
		return err
	}
	deleteBlobsAfterCommit(ctx, tx, s.bucket, f)
	return nil
}

// primaryText is the saved record's primary key as system_files stores it
// in attachment_id (Winter keeps the morph key as a string).
func primaryText(model any) string {
	if n := pkUint(model); n > 0 {
		return uitoa(n)
	}
	return ""
}