package edit

import (
	"os"
	"os/exec"
	"strings"

	"src.elv.sh/pkg/cli"
	"src.elv.sh/pkg/edit/highlight"
	"src.elv.sh/pkg/eval"
	"src.elv.sh/pkg/fsutil"
	"src.elv.sh/pkg/parse"
	"src.elv.sh/pkg/ui"
)

func initHighlighter(appSpec *cli.AppSpec, ed *Editor, ev *eval.Evaler, nb eval.NsBuilder) {
	hl := highlight.NewHighlighter(highlight.Config{
		Check: func(t parse.Tree) (string, error) {
			autofixes, err := ev.CheckTree(t, nil)
			autofix := strings.Join(autofixes, "; ")
			ed.autofix.Store(autofix)
			return autofix, err
		},
		HasCommand: func(cmd string) bool { return hasCommand(ev, cmd) },
		AutofixTip: func(autofix string) ui.Text {
			return bindingTips(ed.ns, "insert:binding",
				bindingTip("autofix: "+autofix, "apply-autofix"),
				bindingTip("autofix first", "smart-enter", "completion:smart-start"))
		},
	})
	appSpec.Highlighter = hl
	ed.applyAutofix = func() {
		code := ed.autofix.Load().(string)
		if code == "" {
			return
		}
		// TODO: Check errors.
		//
		// For now, the autofix snippets are simple enough that we know they'll
		// always succeed.
		ev.Eval(parse.Source{Name: "[autofix]", Code: code}, eval.EvalCfg{})
		hl.InvalidateCache()
	}
	nb.AddGoFn("apply-autofix", ed.applyAutofix)
}

func hasCommand(ev *eval.Evaler, cmd string) bool {
	if eval.IsBuiltinSpecial[cmd] {
		return true
	}
	if fsutil.DontSearch(cmd) {
		return isDirOrExecutable(cmd) || hasExternalCommand(cmd)
	}

	sigil, qname := eval.SplitSigil(cmd)
	if sigil != "" {
		// The @ sign is only valid when referring to external commands.
		return hasExternalCommand(cmd)
	}

	first, rest := eval.SplitQName(qname)
	switch {
	case rest == "":
		// Unqualified name; try builtin and global.
		if hasFn(ev.Builtin(), first) || hasFn(ev.Global(), first) {
			return true
		}
	case first == "e:":
		return hasExternalCommand(rest)
	default:
		// Qualified name. Find the top-level module first.
		if hasQualifiedFn(ev, first, rest) {
			return true
		}
	}

	// If all failed, it can still be an external command.
	return hasExternalCommand(cmd)
}

func hasQualifiedFn(ev *eval.Evaler, firstNs string, rest string) bool {
	if rest == "" {
		return false
	}
	modVal, ok := ev.Global().Index(firstNs)
	if !ok {
		modVal, ok = ev.Builtin().Index(firstNs)
		if !ok {
			return false
		}
	}
	mod, ok := modVal.(*eval.Ns)
	if !ok {
		return false
	}
	segs := eval.SplitQNameSegs(rest)
	for _, seg := range segs[:len(segs)-1] {
		modVal, ok = mod.Index(seg)
		if !ok {
			return false
		}
		mod, ok = modVal.(*eval.Ns)
		if !ok {
			return false
		}
	}
	return hasFn(mod, segs[len(segs)-1])
}

func hasFn(ns *eval.Ns, name string) bool {
	fnVar, ok := ns.Index(name + eval.FnSuffix)
	if !ok {
		return false
	}
	_, ok = fnVar.(eval.Callable)
	return ok
}

func isDirOrExecutable(fname string) bool {
	stat, err := os.Stat(fname)
	return err == nil && (stat.IsDir() || fsutil.IsExecutable(stat))
}

func hasExternalCommand(cmd string) bool {
	_, err := exec.LookPath(cmd)
	return err == nil
}
