// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
// All rights reserved.

// operator-plugin.go
package expr

import (
	"fmt"
	"io"
	"plugin"
)

//-------- plugin term

func newPluginTerm(tk *Token) (inst *term) {
	return &term{
		tk:       *tk,
		children: make([]*term, 0, 1),
		position: posPrefix,
		priority: priSign,
		evalFunc: evalPlugin,
	}
}

func importPlugin(ctx ExprContext, dirList []string, name string) (err error) {
	var filePath string
	var p *plugin.Plugin
	var sym plugin.Symbol
	var moduleName string
	var importFunc func(ctx ExprContext)
	var ok bool

	decoratedName := fmt.Sprintf("expr-%s-plugin.so", name)

	if filePath, err = makeFilepath(decoratedName, dirList); err != nil {
		return
	}

	if p, err = plugin.Open(filePath); err != nil {
		return
	}

	if sym, err = p.Lookup("MODULE_NAME"); err != nil {
		return
	}

	if moduleName = *sym.(*string); moduleName == "" {
		err = fmt.Errorf("plugin %q does not provide a valid module name", decoratedName)
		return
	}

	if sym, err = p.Lookup("ImportFuncs"); err != nil {
		return
	}

	if importFunc, ok = sym.(func(ExprContext)); !ok {
		err = fmt.Errorf("plugin %q does not provide a valid import function", decoratedName)
		return
	}

	registerPlugin(moduleName, p)
	importFunc(globalCtx)

	return
}

func evalPlugin(ctx ExprContext, self *term) (v any, err error) {
	var childValue any
	var moduleSpec any

	if childValue, err = self.evalPrefix(ctx); err != nil {
		return
	}

	dirList := buildSearchDirList("plugin", ENV_EXPR_PLUGIN_PATH)
	count := 0
	it := NewAnyIterator(childValue)
	for moduleSpec, err = it.Next(); err == nil; moduleSpec, err = it.Next() {
		if module, ok := moduleSpec.(string); ok {
			if err = importPlugin(ctx, dirList, module); err != nil {
				break
			}
			count++
		} else {
			err = self.Errorf("expected string as item nr %d, got %s", it.Index()+1, typeName(moduleSpec))
			break
		}
	}
	if err == io.EOF {
		err = nil
	}

	if err == nil {
		v = int64(count)
	}
	return
}

// init
func init() {
	registerTermConstructor(SymKwPlugin, newPluginTerm)
}