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

// simple-func-store.go
package expr

import (
	"fmt"
	"strings"
)

type SimpleFuncStore struct {
	SimpleVarStore
	funcStore map[string]*funcInfo
}

type funcInfo struct {
	name    string
	minArgs int
	maxArgs int
	functor Functor
}

func (info *funcInfo) ToString(opt FmtOpt) string {
	var sb strings.Builder
	var i int
	sb.WriteString("func(")
	for i = 0; i < info.minArgs; i++ {
		if i > 0 {
			sb.WriteString(", ")
		}
		sb.WriteString(fmt.Sprintf("arg%d", i+1))
	}
	for ; i < info.maxArgs; i++ {
		sb.WriteString(fmt.Sprintf("arg%d", i+1))
	}
	if info.maxArgs < 0 {
		if info.minArgs > 0 {
			sb.WriteString(", ")
		}
		sb.WriteString("...")
	}
	sb.WriteString(") {...}")
	return sb.String()
}

func (info *funcInfo) Name() string {
	return info.name
}

func (info *funcInfo) MinArgs() int {
	return info.minArgs
}

func (info *funcInfo) MaxArgs() int {
	return info.maxArgs
}

func (info *funcInfo) Functor() Functor {
	return info.functor
}

func NewSimpleFuncStore() *SimpleFuncStore {
	ctx := &SimpleFuncStore{
		SimpleVarStore: SimpleVarStore{varStore: make(map[string]any)},
		funcStore:      make(map[string]*funcInfo),
	}
	ImportBuiltinsFuncs(ctx)
	return ctx
}

func (ctx *SimpleFuncStore) Clone() ExprContext {
	svs := ctx.SimpleVarStore
	return &SimpleFuncStore{
		// SimpleVarStore: SimpleVarStore{varStore: CloneMap(ctx.varStore)},
		SimpleVarStore: SimpleVarStore{varStore: svs.cloneVars()},
		funcStore:      CloneFilteredMap(ctx.funcStore, func(name string) bool { return name[0] != '@' }),
	}
}

func funcsCtxToBuilder(sb *strings.Builder, ctx ExprContext, indent int) {
	sb.WriteString("funcs: {\n")
	first := true
	for _, name := range ctx.EnumFuncs(func(name string) bool { return true }) {
		if first {
			first = false
		} else {
			sb.WriteByte(',')
			sb.WriteByte('\n')
		}
		value, _ := ctx.GetFuncInfo(name)
		sb.WriteString(strings.Repeat("\t", indent+1))
		sb.WriteString(name)
		sb.WriteString("=")
		if formatter, ok := value.(Formatter); ok {
			sb.WriteString(formatter.ToString(0))
		} else {
			sb.WriteString(fmt.Sprintf("%v", value))
		}
	}
	sb.WriteString("\n}\n")
}

func (ctx *SimpleFuncStore) ToString(opt FmtOpt) string {
	var sb strings.Builder
	sb.WriteString(ctx.SimpleVarStore.ToString(opt))
	funcsCtxToBuilder(&sb, ctx, 0)
	return sb.String()
}

func (ctx *SimpleFuncStore) GetFuncInfo(name string) (info ExprFunc, exists bool) {
	info, exists = ctx.funcStore[name]
	return
}

func (ctx *SimpleFuncStore) RegisterFunc(name string, functor Functor, minArgs, maxArgs int) {
	ctx.funcStore[name] = &funcInfo{name: name, minArgs: minArgs, maxArgs: maxArgs, functor: functor}
}

func (ctx *SimpleFuncStore) EnumFuncs(acceptor func(name string) (accept bool)) (funcNames []string) {
	funcNames = make([]string, 0)
	for name := range ctx.funcStore {
		if acceptor != nil {
			if acceptor(name) {
				funcNames = append(funcNames, name)
			}
		} else {
			funcNames = append(funcNames, name)
		}
	}
	return
}

func (ctx *SimpleFuncStore) Call(name string, args []any) (result any, err error) {
	if info, exists := ctx.funcStore[name]; exists {
		functor := info.functor
		result, err = functor.Invoke(ctx, name, args)
	} else {
		err = fmt.Errorf("unknown function %s()", name)
	}
	return
}