package cabana

import (
	"context"
	"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"
)

// 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). 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; binds attach their pending file, and the
// applied rows are deleted. Bindings of other fields stay for the purge.
func (s CRUDService) commitDeferred(ctx context.Context, tx *gorm.DB, cc *CompiledController, target any, op string, in RecordInput) error {
	if cc == nil || len(cc.files) == 0 || in.SessionKey == "" {
		return nil
	}
	principal, _ := bouncer.User(ctx)
	if principal == nil || !principal.Backend || principal.ID == 0 {
		return nil
	}
	fields := make([]string, 0, len(cc.files))
	for _, field := range cc.Form.Fields {
		if cf := cc.files[field.Name]; cf != nil && contextAllows(cc, cf.name, op) {
			fields = append(fields, cf.name)
		}
	}
	if len(fields) == 0 {
		return nil
	}
	morph, err := lagoon.MorphType(tx, target)
	if err != nil {
		return lifecycleFailure(cc, err)
	}
	key := lagoon.DeferredKey{SessionKey: in.SessionKey, AdminID: principal.ID, MasterType: morph}
	rows, err := lagoon.DeferredBindings(ctx, tx, key, fields)
	if err != nil {
		return lifecycleFailure(cc, err)
	}
	ownerID := primaryText(target)
	if ownerID == "" {
		return nil
	}
	applied := make([]uint, 0, len(rows))
	for _, row := range rows {
		cf := cc.files[row.MasterField]
		if cf == nil || row.SlaveType != lagoon.DeferredFileType || !row.IsBind {
			continue
		}
		if err := s.applyFileBind(ctx, tx, cf, morph, ownerID, row); err != nil {
			return lifecycleFailure(cc, err)
		}
		applied = append(applied, row.ID)
	}
	if err := lagoon.DeferredForget(ctx, tx, applied); err != nil {
		return lifecycleFailure(cc, err)
	}
	return nil
}

// applyFileBind attaches a pending upload to the owner. A row that is gone
// or already attached somewhere is ignored.
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
	}
	return tx.Session(&gorm.Session{NewDB: true, Context: ctx}).Model(&attach.File{}).
		Where("id = ?", f.ID).
		Updates(map[string]any{"attachment_type": morph, "attachment_id": ownerID, "field": cf.name}).Error
}

// 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 ""
}