Added csv:to-csv

_docs/mod/csv.md

@@ -27,3 +27,14 @@ csv:each-record "winds.csv" { |row hdr|
   echo "Wind $name has bearing $bearing"
 }
 ```
+
+```
+csv:to-csv CONT [-header HEADER]
+```
+
+Produces a CSV using the items of CONT and writes it as a string. CONT must be a list of iterator of hashable
+elements.
+
+If HEADER is defined, it must be a list of strings identifying the name and order of the hash keys to read
+from each hashable item of CONT. If HEADER is not defined, then the keys of the first consumed hashable item will be
+used, with the keys sorted in alphabetical order.

ucl/builtins.go

@@ -340,8 +340,8 @@ func objectsEqual(l, r Object) bool {
 			}
 		}
 		return true
-	case hashable:
+	case Hashable:
-		rv, ok := r.(hashable)
+		rv, ok := r.(Hashable)
 		if !ok {
 			return false
 		}
@@ -462,7 +462,7 @@ func lenBuiltin(ctx context.Context, args invocationArgs) (Object, error) {
 		return IntObject(len(string(v))), nil
 	case Listable:
 		return IntObject(v.Len()), nil
-	case hashable:
+	case Hashable:
 		return IntObject(v.Len()), nil
 	case Iterable:
 		cnt := 0
@@ -490,7 +490,7 @@ func indexLookup(ctx context.Context, obj, elem Object) (Object, error) {
 			return v.Index(int(intIdx)), nil
 		}
 		return nil, nil
-	case hashable:
+	case Hashable:
 		strIdx, ok := elem.(StringObject)
 		if !ok {
 			return nil, errors.New("expected string for hashable")
@@ -524,7 +524,7 @@ func keysBuiltin(ctx context.Context, args invocationArgs) (Object, error) {
 
 	val := args.args[0]
 	switch v := val.(type) {
-	case hashable:
+	case Hashable:
 		keys := make(ListObject, 0, v.Len())
 		if err := v.Each(func(k string, _ Object) error {
 			keys = append(keys, StringObject(k))
@@ -669,7 +669,7 @@ func filterBuiltin(ctx context.Context, args invocationArgs) (Object, error) {
 			}
 		}
 		return &newList, nil
-	case hashable:
+	case Hashable:
 		newHash := hashObject{}
 		if err := t.Each(func(k string, v Object) error {
 			if m, err := inv.invoke(ctx, args.fork([]Object{StringObject(k), v})); err != nil {
@@ -734,7 +734,7 @@ func reduceBuiltin(ctx context.Context, args invocationArgs) (Object, error) {
 			accum = newAccum
 		}
 		return accum, nil
-	case hashable:
+	case Hashable:
 		// TODO: should raise error?
 		if err := t.Each(func(k string, v Object) error {
 			newAccum, err := block.invoke(ctx, args.fork([]Object{StringObject(k), v, accum}))
@@ -1031,7 +1031,7 @@ func foreachBuiltin(ctx context.Context, args macroArgs) (Object, error) {
 				}
 			}
 		}
-	case hashable:
+	case Hashable:
 		err := t.Each(func(k string, v Object) error {
 			last, err = args.evalBlock(ctx, blockIdx, []Object{StringObject(k), v}, true)
 			return err

ucl/builtins/csv.go

@@ -4,9 +4,11 @@ import (
 	"context"
 	"encoding/csv"
 	"errors"
+	"fmt"
 	"io"
 	"io/fs"
 	"os"
+	"sort"
 	"strings"
 	"ucl.lmika.dev/ucl"
 )
@@ -22,6 +24,7 @@ func CSV(fs fs.FS) ucl.Module {
 		Name: "csv",
 		Builtins: map[string]ucl.BuiltinHandler{
 			"each-record": fsh.eachRecord,
+			"to-csv":      fsh.toCsv,
 		},
 	}
 }
@@ -76,6 +79,129 @@ func (h csvHandlers) eachRecord(ctx context.Context, args ucl.CallArgs) (any, er
 	return nil, nil
 }
 
+func (h csvHandlers) toCsv(ctx context.Context, args ucl.CallArgs) (any, error) {
+	var rowConsumer func() (ucl.Object, error)
+
+	var (
+		listable ucl.Listable
+		iterable ucl.Iterable
+	)
+	if args.CanBind(&listable) {
+		if err := args.Bind(&listable); err != nil {
+			return nil, err
+		}
+
+		rowConsumer = func() func() (ucl.Object, error) {
+			idx := 0
+			return func() (ucl.Object, error) {
+				if idx >= listable.Len() {
+					return nil, io.EOF
+				}
+
+				v := listable.Index(idx)
+				idx += 1
+				return v, nil
+			}
+		}()
+	} else if args.CanBind(&iterable) {
+		if err := args.Bind(&iterable); err != nil {
+			return nil, err
+		}
+
+		rowConsumer = func() func() (ucl.Object, error) {
+			return func() (ucl.Object, error) {
+				if !iterable.HasNext() {
+					return nil, io.EOF
+				}
+
+				return iterable.Next(ctx)
+			}
+		}()
+	} else {
+		return nil, errors.New("unsupported type")
+	}
+
+	var (
+		header []string
+		row    []string
+	)
+	if args.HasSwitch("header") {
+		var headerListable ucl.Listable
+
+		if err := args.BindSwitch("header", &headerListable); err != nil {
+			return nil, err
+		}
+		if headerListable.Len() == 0 {
+			return nil, errors.New("header requires at least one item")
+		}
+
+		header = make([]string, headerListable.Len())
+		for i := range header {
+			header[i] = headerListable.Index(i).String()
+		}
+
+		row = make([]string, len(header))
+	}
+
+	var sb strings.Builder
+	cw := csv.NewWriter(&sb)
+
+	i := 0
+	for {
+		v, err := rowConsumer()
+		if err != nil {
+			if errors.Is(err, io.EOF) {
+				break
+			} else {
+				return nil, err
+			}
+		}
+
+		hv, ok := v.(ucl.Hashable)
+		if !ok {
+			return nil, fmt.Errorf("element %v is not hashable", i)
+		}
+
+		if len(header) == 0 {
+			if err := hv.Each(func(k string, _ ucl.Object) error {
+				header = append(header, k)
+				return nil
+			}); err != nil {
+				return nil, err
+			}
+
+			sort.Strings(header)
+			row = make([]string, len(header))
+		}
+		if i == 0 {
+			if err := cw.Write(header); err != nil {
+				return nil, err
+			}
+		}
+
+		for j, k := range header {
+			val := hv.Value(k)
+			if val == nil {
+				row[j] = ""
+			} else {
+				row[j] = val.String()
+			}
+		}
+
+		if err := cw.Write(row); err != nil {
+			return nil, err
+		}
+
+		i++
+	}
+
+	cw.Flush()
+	if err := cw.Error(); err != nil {
+		return nil, err
+	}
+	return sb.String(), nil
+}
+
 type headerIndexObject map[string]int
 
 func (hio headerIndexObject) String() string {

ucl/builtins/csv_test.go

@@ -51,3 +51,48 @@ func TestCSV_ReadRecord(t *testing.T) {
 		})
 	}
 }
+
+func TestCSV_ToCSV(t *testing.T) {
+	tests := []struct {
+		descr string
+		eval  string
+		want  string
+	}{
+		{
+			descr: "to csv 1",
+			eval:  `csv:to-csv [[hello:"one"] [hello:"two"]]`,
+			want:  "hello\none\ntwo\n",
+		},
+		{
+			descr: "to csv 2",
+			eval:  `csv:to-csv [[hello:"one" world:"this"] [hello:"two" world:"that"]]`,
+			want:  "hello,world\none,this\ntwo,that\n",
+		},
+		{
+			descr: "to csv 3",
+			eval:  `csv:to-csv [[hello:"one" world:"this"] [hello:"two" other:"the" world:"that"]] -header [world other]`,
+			want:  "world,other\nthis,\nthat,the\n",
+		},
+		{
+			descr: "to csv 4",
+			eval:  `itrs:from [[hello:"one" world:"this"] [hello:"two" other:"the" world:"that"]] | csv:to-csv -header [world other]`,
+			want:  "world,other\nthis,\nthat,the\n",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.descr, func(t *testing.T) {
+			var bfr bytes.Buffer
+
+			inst := ucl.New(
+				ucl.WithModule(builtins.CSV(testCsvFS)),
+				ucl.WithModule(builtins.Itrs()),
+				ucl.WithOut(&bfr),
+			)
+
+			res, err := inst.Eval(context.Background(), tt.eval)
+			assert.NoError(t, err)
+			assert.Equal(t, tt.want, res)
+		})
+	}
+}

ucl/objs.go

@@ -40,7 +40,7 @@ type ModListable interface {
 	Insert(idx int, obj Object) error
 }
 
-type hashable interface {
+type Hashable interface {
 	Len() int
 	Value(k string) Object
 	Each(func(k string, v Object) error) error

ucl/userbuiltin.go

@@ -186,6 +186,12 @@ func canBindArg(v interface{}, arg Object) bool {
 	case *int:
 		_, ok := arg.(IntObject)
 		return ok
+	case *Listable:
+		_, ok := arg.(Listable)
+		return ok
+	case *Iterable:
+		_, ok := arg.(Iterable)
+		return ok
 	}
 
 	switch t := arg.(type) {