first commit

plugin/filter/engine.go

@@ -0,0 +1,191 @@
+package filter
+
+import (
+	"context"
+	"fmt"
+	"strings"
+	"sync"
+
+	"github.com/google/cel-go/cel"
+	"github.com/pkg/errors"
+)
+
+// Engine parses CEL filters into a dialect-agnostic condition tree.
+type Engine struct {
+	schema Schema
+	env    *cel.Env
+}
+
+// NewEngine builds a new Engine for the provided schema.
+func NewEngine(schema Schema) (*Engine, error) {
+	env, err := cel.NewEnv(schema.EnvOptions...)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to create CEL environment")
+	}
+	return &Engine{
+		schema: schema,
+		env:    env,
+	}, nil
+}
+
+// Program stores a compiled filter condition.
+type Program struct {
+	schema    Schema
+	condition Condition
+}
+
+// ConditionTree exposes the underlying condition tree.
+func (p *Program) ConditionTree() Condition {
+	return p.condition
+}
+
+// Compile parses the filter string into an executable program.
+func (e *Engine) Compile(_ context.Context, filter string) (*Program, error) {
+	if strings.TrimSpace(filter) == "" {
+		return nil, errors.New("filter expression is empty")
+	}
+
+	filter = normalizeLegacyFilter(filter)
+
+	ast, issues := e.env.Compile(filter)
+	if issues != nil && issues.Err() != nil {
+		return nil, errors.Wrap(issues.Err(), "failed to compile filter")
+	}
+	parsed, err := cel.AstToParsedExpr(ast)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed to convert AST")
+	}
+
+	cond, err := buildCondition(parsed.GetExpr(), e.schema)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Program{
+		schema:    e.schema,
+		condition: cond,
+	}, nil
+}
+
+// CompileToStatement compiles and renders the filter in a single step.
+func (e *Engine) CompileToStatement(ctx context.Context, filter string, opts RenderOptions) (Statement, error) {
+	program, err := e.Compile(ctx, filter)
+	if err != nil {
+		return Statement{}, err
+	}
+	return program.Render(opts)
+}
+
+// RenderOptions configure SQL rendering.
+type RenderOptions struct {
+	Dialect           DialectName
+	PlaceholderOffset int
+	DisableNullChecks bool
+}
+
+// Statement contains the rendered SQL fragment and its args.
+type Statement struct {
+	SQL  string
+	Args []any
+}
+
+// Render converts the program into a dialect-specific SQL fragment.
+func (p *Program) Render(opts RenderOptions) (Statement, error) {
+	renderer := newRenderer(p.schema, opts)
+	return renderer.Render(p.condition)
+}
+
+var (
+	defaultOnce           sync.Once
+	defaultInst           *Engine
+	defaultErr            error
+	defaultAttachmentOnce sync.Once
+	defaultAttachmentInst *Engine
+	defaultAttachmentErr  error
+)
+
+// DefaultEngine returns the process-wide memo filter engine.
+func DefaultEngine() (*Engine, error) {
+	defaultOnce.Do(func() {
+		defaultInst, defaultErr = NewEngine(NewSchema())
+	})
+	return defaultInst, defaultErr
+}
+
+// DefaultAttachmentEngine returns the process-wide attachment filter engine.
+func DefaultAttachmentEngine() (*Engine, error) {
+	defaultAttachmentOnce.Do(func() {
+		defaultAttachmentInst, defaultAttachmentErr = NewEngine(NewAttachmentSchema())
+	})
+	return defaultAttachmentInst, defaultAttachmentErr
+}
+
+func normalizeLegacyFilter(expr string) string {
+	expr = rewriteNumericLogicalOperand(expr, "&&")
+	expr = rewriteNumericLogicalOperand(expr, "||")
+	return expr
+}
+
+func rewriteNumericLogicalOperand(expr, op string) string {
+	var builder strings.Builder
+	n := len(expr)
+	i := 0
+	var inQuote rune
+
+	for i < n {
+		ch := expr[i]
+
+		if inQuote != 0 {
+			builder.WriteByte(ch)
+			if ch == '\\' && i+1 < n {
+				builder.WriteByte(expr[i+1])
+				i += 2
+				continue
+			}
+			if ch == byte(inQuote) {
+				inQuote = 0
+			}
+			i++
+			continue
+		}
+
+		if ch == '\'' || ch == '"' {
+			inQuote = rune(ch)
+			builder.WriteByte(ch)
+			i++
+			continue
+		}
+
+		if strings.HasPrefix(expr[i:], op) {
+			builder.WriteString(op)
+			i += len(op)
+
+			// Preserve whitespace following the operator.
+			wsStart := i
+			for i < n && (expr[i] == ' ' || expr[i] == '\t') {
+				i++
+			}
+			builder.WriteString(expr[wsStart:i])
+
+			signStart := i
+			if i < n && (expr[i] == '+' || expr[i] == '-') {
+				i++
+			}
+			for i < n && expr[i] >= '0' && expr[i] <= '9' {
+				i++
+			}
+			if i > signStart {
+				numLiteral := expr[signStart:i]
+				builder.WriteString(fmt.Sprintf("(%s != 0)", numLiteral))
+			} else {
+				builder.WriteString(expr[signStart:i])
+			}
+			continue
+		}
+
+		builder.WriteByte(ch)
+		i++
+	}
+
+	return builder.String()
+}