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

// builtin-iterator.go
package expr

import (
	"fmt"
	"io"

	"git.portale-stac.it/go-pkg/expr/kern"
)

const (
	iterParamOperator = "operator"
	iterParamVars     = "vars"
	iterVarStatus     = "status"
)

func parseRunArgs(localCtx kern.ExprContext, args map[string]any) (it kern.Iterator, op kern.Functor, err error) {
	var ok bool

	if it, ok = args[kern.ParamIterator].(kern.Iterator); !ok {
		err = fmt.Errorf("paramter %q must be an iterator, passed %v [%s]", kern.ParamIterator, args[kern.ParamIterator], kern.TypeName(args[kern.ParamIterator]))
		return
	}

	if args[iterParamOperator] != nil {
		if op, ok = args[iterParamOperator].(kern.Functor); !ok || op == nil {
			err = fmt.Errorf("paramter %q must be a function, passed %v [%s]", iterParamOperator, args[iterParamOperator], kern.TypeName(args[iterParamOperator]))
			return
		}
	}

	var vars *kern.DictType
	if vars, ok = args[iterParamVars].(*kern.DictType); !ok && args[iterParamVars] != nil {
		err = fmt.Errorf("paramter %q must be a dictionary, passed %v [%s]", iterParamVars, args[iterParamVars], kern.TypeName(args[iterParamVars]))
		return
	}

	if vars != nil {
		for key, value := range *vars {
			var varName string
			if varName, ok = key.(string); ok {
				localCtx.UnsafeSetVar(varName, value)
			}
		}
	}

	return
}

func runFunc(ctx kern.ExprContext, name string, args map[string]any) (result any, err error) {
	var it kern.Iterator
	var ok bool
	var op kern.Functor
	var v any
	// var usingDefaultOp = false
	var params map[string]any
	var item any

	localCtx := ctx.Clone()
	localCtx.UnsafeSetVar(iterVarStatus, nil)

	if it, op, err = parseRunArgs(localCtx, args); err != nil {
		return
	}

	for item, err = it.Next(); err == nil; item, err = it.Next() {
		if op != nil {
			params = map[string]any{kern.ParamIndex: it.Index(), kern.ParamItem: item}
			if v, err = op.InvokeNamed(localCtx, iterParamOperator, params); err != nil {
				break
			} else {
				var success bool
				if success, ok = kern.ToBool(v); !success || !ok {
					break
				}
			}
		}
	}

	if err == io.EOF {
		err = nil
	}
	if err == nil {
		if op == nil {
			ctx.UnsafeSetVar(iterVarStatus, it.Count())
		}
		result, _ = localCtx.GetVar(iterVarStatus)
	}
	return
}

func ImportIterFuncs(ctx kern.ExprContext) {
	ctx.RegisterFunc("run", kern.NewGolangFunctor(runFunc), kern.TypeAny, []kern.ExprFuncParam{
		NewFuncParam(kern.ParamIterator),
		NewFuncParamFlag(iterParamOperator, PfOptional),
		NewFuncParamFlag(iterParamVars, PfOptional),
	})
}

func init() {
	RegisterBuiltinModule("iterator", ImportIterFuncs, "Iterator helper functions")
}