Start implementing Starlark execution environment

Signed-off-by: Nicolas Paul <n@nc0.fr>

1 files changed, 98 insertions, 0 deletions

diff --git a/pkg/config/starlark.go b/pkg/config/starlark.go
new file mode 100644
index 0000000..39adcf9
--- /dev/null
+++ b/pkg/config/starlark.go
@@ -0,0 +1,98 @@
+package config
+
+import (
+	"fmt"
+	"go.nc0.fr/svgu/pkg/types"
+	"go.starlark.net/starlark"
+)
+
+var registered types.Index
+
+// ExecConfig configures the Starlark environment and executes the given
+// configuration file "fl".
+// The function returns a list of registered modules, or an error if something
+// went wrong.
+func ExecConfig(fl string) (*types.Index, error) {
+	th := &starlark.Thread{
+		Name: "exec " + fl,
+		Load: load,
+	}
+
+	// TODO(nc0): add built-ins
+	env := starlark.StringDict{
+		"index":  starlark.NewBuiltin("index", InternIndex),
+		"module": starlark.NewBuiltin("module", InternModule),
+	}
+
+	registered = types.Index{}
+	if _, err := starlark.ExecFile(th, fl, nil, env); err != nil {
+		return &types.Index{}, err
+	}
+
+	return &registered, nil
+}
+
+// load loads a module from the given path.
+func load(t *starlark.Thread, module string) (starlark.StringDict, error) {
+	switch module {
+	// todo: add libs
+	}
+
+	return nil, fmt.Errorf("unknown module %q", module)
+}
+
+// Injected built-ins.
+
+// InternIndex represents the built-in function "index".
+// index(domain) initializes a new index with the given domain.
+func InternIndex(thread *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple,
+	kwargs []starlark.Tuple) (starlark.Value, error) {
+	var domain string
+	if err := starlark.UnpackArgs("index", args, kwargs,
+		"domain", &domain); err != nil {
+		return nil, err
+	}
+
+	registered.SetDomain(domain)
+
+	return starlark.None, nil
+}
+
+// InternModule represents the built-in function "module".
+// module(name, vcs, repo, dir=None, file=None) registers a new module into the
+// index.
+func InternModule(_ *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple,
+	kwargs []starlark.Tuple) (starlark.Value, error) {
+
+	var name, vcs, repo, dir, file string
+	if err := starlark.UnpackArgs("module", args, kwargs, "name",
+		&name, "vcs", &vcs, "repo", &repo, "dir?", &dir, "file?", &file); err != nil {
+		return nil, err
+	}
+
+	var v types.Vcs
+	switch vcs {
+	case "git":
+		v = types.VcsGit
+	case "hg":
+		v = types.VcsMercurial
+	case "svn":
+		v = types.VcsSubversion
+	case "fossil":
+		v = types.VcsFossil
+	case "bzr":
+		v = types.VcsBazaar
+	default:
+		return nil, fmt.Errorf("unknown vcs %q", vcs)
+	}
+
+	registered.AddModule(name, types.Module{
+		Path: name,
+		Vcs:  v,
+		Repo: repo,
+		Dir:  dir,
+		File: file,
+	})
+
+	return starlark.None, nil
+}