8 files changed, 191 insertions(+), 0 deletions(-)

A do-thing.lua
M go.mod
M go.sum
M internal/facts/facts.go
A lua.go
M main.go
A share/lua/facts/hostname
A share/lua/facts/os/distribution

@@ 0,0 1,2 @@
+cpuModel = govern:GetFact("sys/cpu/model")
+print(cpuModel)

@@ 9,7 9,9 @@ require (
 	github.com/nesv/cmndr v1.1.0
 	github.com/pkg/errors v0.9.1
 	github.com/rs/xid v0.0.0-20170604230408-02dd45c33376
+	github.com/yuin/gopher-lua v1.1.0
 	github.com/zclconf/go-cty v1.8.0
+	golang.org/x/term v0.6.0
 	k8s.io/apimachinery v0.20.4
 )
 


@@ 20,5 22,6 @@ require (
 	github.com/mitchellh/go-wordwrap v0.0.0-20150314170334-ad45545899c7 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
 	github.com/stretchr/testify v1.7.0 // indirect
+	golang.org/x/sys v0.6.0 // indirect
 	golang.org/x/text v0.3.5 // indirect
 )

@@ 127,6 127,8 @@ github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
 github.com/vmihailenco/msgpack v3.3.3+incompatible/go.mod h1:fy3FlTQTDXWkZ7Bh6AcGMlsjHatGryHQYUTf1ShIgkk=
 github.com/vmihailenco/msgpack/v4 v4.3.12/go.mod h1:gborTTJjAo/GWTqqRjrLCn9pgNN+NXzzngzBKDPIqw4=
 github.com/vmihailenco/tagparser v0.1.1/go.mod h1:OeAg3pn3UbLjkWt+rN9oFYB6u/cQgqMEUPoW2WPyhdI=
+github.com/yuin/gopher-lua v1.1.0 h1:BojcDhfyDWgU2f2TOzYK/g5p2gxMrku8oupLDqlnSqE=
+github.com/yuin/gopher-lua v1.1.0/go.mod h1:GBR0iDaNXjAgGg9zfCvksxSRnQx76gclCIb7kdAd1Pw=
 github.com/zclconf/go-cty v1.2.0/go.mod h1:hOPWgoHbaTUnI5k4D2ld+GRpFJSCe6bCM7m1q/N4PQ8=
 github.com/zclconf/go-cty v1.8.0 h1:s4AvqaeQzJIu3ndv4gVIhplVD0krU+bgrcLSVUnaWuA=
 github.com/zclconf/go-cty v1.8.0/go.mod h1:vVKLxnk3puL4qRAv72AO+W99LUD4da90g3uUAzyuvAk=


@@ 166,6 168,10 @@ golang.org/x/sys v0.0.0-20191005200804-aed5e4c7ecf9/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20201112073958-5cba982894dd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.6.0 h1:MVltZSvRTcU2ljQOhs94SXPftV6DCNnZViHeQps87pQ=
+golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/term v0.6.0 h1:clScbb1cHjoCkyRbWwBEUZ5H/tIFu5TAXIqaZD0Gcjw=
+golang.org/x/term v0.6.0/go.mod h1:m6U89DPEgQRMq3DNkDClhWw02AUbt2daBVO4cn4Hv9U=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=

@@ 172,3 172,16 @@ func (f *Facts) Get(name string) (string, error) {
 	p, err := io.ReadAll(fact)
 	return string(p), errors.Wrap(err, "read fact")
 }
+
+// Names returns the names of all available facts.
+func (f *Facts) Names() []string {
+	f.mu.RLock()
+	defer f.mu.RUnlock()
+
+	names := make([]string, 0, len(f.facts))
+	for name := range f.facts {
+		names = append(names, name)
+	}
+
+	return names
+}

@@ 0,0 1,144 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"github.com/nesv/cmndr"
+	lua "github.com/yuin/gopher-lua"
+	"golang.org/x/term"
+
+	"git.sr.ht/~nesv/govern/internal/facts"
+)
+
+const luaShellBanner = `
+   ____ _____ _   _____  _________ 
+  / __  / __ \ | / / _ \/ ___/ __ \
+ / /_/ / /_/ / |/ /  __/ /  / / / /
+ \__, /\____/|___/\___/_/  /_/ /_/ 
+/____/`
+
+func (c *command) runLuaShell(cmd *cmndr.Cmd, args []string) error {
+	if err := c.init(); err != nil {
+		return err
+	}
+
+	ff, err := c.collectFacts()
+	if err != nil {
+		return fmt.Errorf("collect facts: %w", err)
+	}
+
+	vm := lua.NewState()
+	defer vm.Close()
+
+	vm.PreloadModule("govern", func(state *lua.LState) int {
+		module := state.SetFuncs(state.NewTable(), map[string]lua.LGFunction{
+			"GetFact":        getFact(ff),
+			"AvailableFacts": availableFacts(ff),
+		})
+
+		state.SetField(module, "name", lua.LString("govern"))
+
+		state.Push(module)
+		return 1
+	})
+
+	fmt.Fprintln(os.Stderr, luaShellBanner)
+
+	oldTermState, err := term.MakeRaw(int(os.Stdin.Fd()))
+	if err != nil {
+		return fmt.Errorf("make raw terminal: %w", err)
+	}
+	defer term.Restore(int(os.Stdin.Fd()), oldTermState)
+
+	terminal := term.NewTerminal(&readwriter{
+		r: os.Stdin,
+		w: os.Stdout,
+	}, "govern-> ")
+
+	for {
+		line, err := terminal.ReadLine()
+		if errors.Is(err, io.EOF) {
+			fmt.Fprintln(terminal, "arrivederci!")
+			return nil
+		} else if err != nil {
+			fmt.Fprintln(os.Stderr, "!!", err)
+			continue
+		}
+
+		switch cmd := strings.TrimSpace(line); cmd {
+		case "exit", "quit":
+			fmt.Fprintln(terminal, "g'bye!")
+			return nil
+		}
+
+		// fmt.Fprintf(os.Stderr, "debug: command = %q\r\n", strings.TrimSpace(line))
+
+		if err := vm.DoString(strings.TrimSpace(line)); err != nil {
+			errMsg := strings.ReplaceAll(err.Error(), "\n", "\r\n")
+			fmt.Fprintf(os.Stderr, "%s\r\n", errMsg)
+			continue
+		}
+
+		fmt.Fprint(terminal, "\r")
+	}
+}
+
+func stdio() io.ReadWriter {
+	return &readwriter{r: os.Stdin, w: os.Stdout}
+}
+
+type readwriter struct {
+	r io.Reader
+	w io.Writer
+}
+
+func (rw *readwriter) Read(p []byte) (int, error)  { return rw.r.Read(p) }
+func (rw *readwriter) Write(p []byte) (int, error) { return rw.w.Write(p) }
+
+// NOTE(nesv): When implementing runners in Lua,
+// maybe there shoud be functions regarding each of the supported "states"
+// (e.g. state = "installed").
+// All of the other key = value pairs in a resource block should be passed into
+// each "state function" as a table.
+
+// NOTE(nesv): Even though govern supports writing runners in any language,
+// all govern really cares about is that it's an executable file,
+// users should be able to implement their own govern-flavoured Lua runners
+// following the "state function" approach.
+
+// TODO(nesv): Custom functions.
+// Retrieve a fact.
+
+// getFact is a function that gets loaded into the Lua runtime.
+func getFact(ff *facts.Facts) lua.LGFunction {
+	return func(state *lua.LState) int {
+		name := state.ToString(1)
+		if name == "" {
+			panic("empty string")
+		}
+
+		factValue, err := ff.Get(name)
+		if err != nil {
+			panic(fmt.Sprintf("cannot find fact %q: %s", name, err))
+		}
+
+		state.Push(lua.LString(factValue))
+		return 1
+	}
+}
+
+func availableFacts(ff *facts.Facts) lua.LGFunction {
+	return func(ls *lua.LState) int {
+		names := ls.NewTable()
+		for _, name := range ff.Names() {
+			names.Append(lua.LString(name))
+		}
+
+		ls.Push(names)
+		return 1
+	}
+}

@@ 71,6 71,10 @@ func main() {
 	render.Description = "Render a template to STDOUT"
 	root.AddCmd(render)
 
+	shell := cmndr.New("shell", cmd.runLuaShell)
+	shell.Description = "Drop into a Lua shell"
+	root.AddCmd(shell)
+
 	root.Exec()
 }
 

@@ 0,0 1,6 @@
+-- vim: syntax=lua:ts=4:sts=4:sw=4
+local handle = io.popen("hostname -f", "r")
+local result = string.gsub(handle:read("*a"), "[\r\n]+$", "")
+handle:close()
+
+print(result)

@@ 0,0 1,13 @@
+-- vim: syntax=lua:ts=4:sts=4:sw=4
+local handle = io.open("/etc/os-release", "r")
+	if handle == nil then
+	io.close(handle)
+os.exit(false)
+	end
+
+	for line in handle:lines(1) do
+print(line)
+	end
+
+	local release = string.gsub(handle:read("*a"), "[\r\n]+$", "")
+print(release)