ucl/cmdlang/builtins.go

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package cmdlang
import (
"bufio"
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"context"
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"errors"
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"fmt"
"io"
"os"
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"strings"
)
func echoBuiltin(ctx context.Context, args invocationArgs) (object, error) {
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if len(args.args) == 0 {
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if _, err := fmt.Fprintln(args.inst.Out()); err != nil {
return nil, err
}
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return nil, nil
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}
var line strings.Builder
for _, arg := range args.args {
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if s, ok := arg.(fmt.Stringer); ok {
line.WriteString(s.String())
}
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}
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if _, err := fmt.Fprintln(args.inst.Out(), line.String()); err != nil {
return nil, err
}
return nil, nil
}
func setBuiltin(ctx context.Context, args invocationArgs) (object, error) {
if err := args.expectArgn(2); err != nil {
return nil, err
}
name, err := args.stringArg(0)
if err != nil {
return nil, err
}
newVal := args.args[1]
// TODO: if the value is a stream, consume the stream and save it as a list
args.ec.setVar(name, newVal)
return newVal, nil
}
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func toUpperBuiltin(ctx context.Context, inStream stream, args invocationArgs) (object, error) {
// Handle args
return mapFilterStream{
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in: inStream,
mapFn: func(x object) (object, bool) {
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s, ok := x.(strObject)
if !ok {
return nil, false
}
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return strObject(strings.ToUpper(string(s))), true
},
}, nil
}
func catBuiltin(ctx context.Context, args invocationArgs) (object, error) {
if err := args.expectArgn(1); err != nil {
return nil, err
}
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filename, err := args.stringArg(0)
if err != nil {
return nil, err
}
return &fileLinesStream{filename: filename}, nil
}
type fileLinesStream struct {
filename string
f *os.File
scnr *bufio.Scanner
}
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func (f *fileLinesStream) String() string {
return fmt.Sprintf("fileLinesStream{file: %v}", f.filename)
}
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func (f *fileLinesStream) Truthy() bool {
return true // ??
}
func (f *fileLinesStream) next() (object, error) {
var err error
// We open the file on the first pull. That way, an unconsumed stream won't result in a FD leak
if f.f == nil {
f.f, err = os.Open(f.filename)
if err != nil {
return nil, err
}
f.scnr = bufio.NewScanner(f.f)
}
if f.scnr.Scan() {
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return strObject(f.scnr.Text()), nil
}
if f.scnr.Err() == nil {
return nil, io.EOF
}
return nil, f.scnr.Err()
}
func (f *fileLinesStream) close() error {
if f.f != nil {
return f.f.Close()
}
return nil
}
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func ifBuiltin(ctx context.Context, args macroArgs) (object, error) {
if args.nargs() < 2 {
return nil, errors.New("need at least 2 arguments")
}
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if guard, err := args.evalArg(ctx, 0); err == nil && isTruthy(guard) {
return args.evalBlock(ctx, 1)
} else if err != nil {
return nil, err
}
args.shift(2)
for args.identIs(ctx, 0, "elif") {
args.shift(1)
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if args.nargs() < 2 {
return nil, errors.New("need at least 2 arguments")
}
if guard, err := args.evalArg(ctx, 0); err == nil && isTruthy(guard) {
return args.evalBlock(ctx, 1)
} else if err != nil {
return nil, err
}
args.shift(2)
}
if args.identIs(ctx, 0, "else") && args.nargs() > 1 {
return args.evalBlock(ctx, 1)
} else if args.nargs() == 0 {
// no elif or else
return nil, nil
}
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return nil, errors.New("malformed if-elif-else")
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}