package cabana

import (
	"context"
	"errors"
	"net/http"
	"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"

// 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
}

// commitDeferred applies the file 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 allowed
// in op, locked FOR UPDATE so two saves with one key serialize, and applies
// them in id order: a bind attaches its pending upload (on an attachOne
// field after deleting the file it replaces), an unbind deletes the attached
// file. Blobs of deleted files are removed after commit, and 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; otherwise the save fails with a 422 on the field,
// the transaction rolls back and the bindings stay 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 || len(cc.files) == 0 {
		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)
		}
	}
	ownerID := primaryText(target)
	if len(fields) == 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, len(fields))
		for i, cf := range fields {
			names[i] = cf.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)
		}
		applied := make([]uint, 0, len(rows))
		for _, row := range rows {
			cf := cc.files[row.MasterField]
			if cf == nil || row.SlaveType != lagoon.DeferredFileType {
				continue
			}
			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)
		}
		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{fileMessage(ctx, s.tr, "required", cf.name, nil)}
		case cf.relation.Many && cf.maxFiles > 0 && n > int64(cf.maxFiles):
			details[cf.name] = []string{fileMessage(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
}

// 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 ""
}