sqlite: basic editing support

db_sqlite.go

@@ -1,10 +1,12 @@
 package main
 
 import (
+	"context"
 	"database/sql"
 	"errors"
 	"fmt"
 	"path/filepath"
+	"strings"
 	"unsafe"
 
 	_ "yvbolt/sqliteclidriver"
@@ -187,6 +189,127 @@ func (ld *sqliteLoadedDatabase) ExecQuery(query string, resultArea *vcl.TStringG
 	return nil
 }
 
+func (n *sqliteLoadedDatabase) ApplyChanges(f *TMainForm, ndata *navData) (retErr error) {
+
+	if len(ndata.bucketPath) != 2 {
+		return errors.New("invalid selection")
+	}
+	tableName := ndata.bucketPath[1]
+
+	// We have rendered row IDs, need to convert back to an SQLite primary key
+	// TODO stash the real key inside f.contentBox.Objects()
+	// FIXME breaks if you try and edit the primary key(!)
+
+	ctx := context.Background()
+
+	tx, err := n.db.BeginTx(ctx, nil)
+	if err != nil {
+		return err
+	}
+
+	var commitOK bool = false
+	defer func() {
+		if !commitOK {
+			err := tx.Rollback()
+			if err != nil {
+				retErr = err
+			}
+		}
+	}()
+
+	// Data grid properties
+	var columnNames []string
+	for i := int32(0); i < f.contentBox.ColCount(); i++ {
+		columnNames = append(columnNames, f.contentBox.Columns().Items(i).Title().Caption())
+	}
+
+	// Query sqlite table metadata to determine which of these is the PRIMARY KEY
+	var primaryColumnName string
+	err = tx.QueryRowContext(ctx, `SELECT l.name FROM pragma_table_info(?) as l WHERE l.pk = 1;`, tableName).Scan(&primaryColumnName)
+	if err != nil {
+		return fmt.Errorf("Finding primary key for update: %w", err)
+	}
+
+	// Convert it to an index
+	var primaryColumnIdx int = -1
+	for i := 0; i < len(columnNames); i++ {
+		if columnNames[i] == primaryColumnName {
+			primaryColumnIdx = i
+			break
+		}
+	}
+	if primaryColumnIdx == -1 {
+		return fmt.Errorf("Primary key %q missing from available columns", primaryColumnName)
+	}
+
+	// SQLite can only LIMIT 1 on update/delete if it was compiled with
+	// SQLITE_ENABLE_UPDATE_DELETE_LIMIT, which isn't the case for the mattn
+	// cgo library
+	// Skip that, and just rely on primary key uniqueness
+
+	// Edit
+	for rowid, editcells := range f.updateRows {
+		stmt := `UPDATE "` + tableName + `" SET `
+		params := []interface{}{} // FIXME reinstate types for the driver (although SQLite doesn't mind)
+
+		for ct, cell := range editcells {
+			if ct > 0 {
+				stmt += `, `
+			}
+			stmt += `"` + columnNames[cell] + `" = ?`
+			params = append(params, f.contentBox.Cells(cell, rowid))
+		}
+		stmt += ` WHERE "` + primaryColumnName + `" = ?`
+		pkVal := f.contentBox.Cells(int32(primaryColumnIdx), rowid)
+		params = append(params, pkVal)
+
+		_, err = tx.ExecContext(ctx, stmt, params...)
+		if err != nil {
+			return fmt.Errorf("Updating row %q: %w", pkVal, err)
+		}
+	}
+
+	// Delete by key (affects rowids after re-render)
+	for rowid, _ := range f.deleteRows {
+		pkVal := f.contentBox.Cells(int32(primaryColumnIdx), rowid)
+
+		stmt := `DELETE FROM "` + tableName + `" WHERE "` + primaryColumnName + `" = ?`
+
+		_, err = tx.ExecContext(ctx, stmt, pkVal)
+		if err != nil {
+			return fmt.Errorf("Deleting row %q: %w", pkVal, err)
+		}
+	}
+
+	// Insert all new entries
+	for rowid, _ := range f.insertRows {
+		stmt := `INSERT INTO "` + tableName + `" (` + strings.Join(columnNames, `, `) + `) VALUES (`
+		params := []interface{}{} // FIXME reinstate types for the driver (although SQLite doesn't mind)
+
+		for colid := 0; colid < len(columnNames); colid++ {
+			if colid > 0 {
+				stmt += `, `
+			}
+			stmt += "?"
+			params = append(params, f.contentBox.Cells(int32(colid), rowid))
+		}
+		stmt += `)`
+
+		_, err = tx.ExecContext(ctx, stmt, params...)
+		if err != nil {
+			return fmt.Errorf("Inserting row: %w", err)
+		}
+	}
+
+	err = tx.Commit()
+	if err != nil {
+		return err
+	}
+
+	commitOK = true // no need for rollback
+	return nil
+}
+
 func (ld *sqliteLoadedDatabase) NavChildren(ndata *navData) ([]string, error) {
 
 	if len(ndata.bucketPath) == 0 {