// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
// All rights reserved.

// func-info.go
package kern

import (
	"fmt"
	"strings"
)

// --- Functions

// FuncInfo implements expr.ExprFunc
type FuncInfo struct {
	name         string
	minArgs      int
	maxArgs      int
	functor      Functor
	formalParams []ExprFuncParam
	returnType   string
}

func NewFuncInfo(name string, functor Functor, returnType string, params []ExprFuncParam) (info *FuncInfo, err error) {
	var minArgs = 0
	var maxArgs = 0
	for _, p := range params {
		if maxArgs == -1 {
			return nil, fmt.Errorf("no more params can be specified after the ellipsis symbol: %q", p.Name())
		}
		if p.IsDefault() || p.IsOptional() {
			maxArgs++
		} else if maxArgs == minArgs {
			minArgs++
			maxArgs++
		} else {
			return nil, fmt.Errorf("can't specify non-optional param after optional ones: %q", p.Name())
		}
		if p.IsRepeat() {
			minArgs--
			maxArgs = -1
		}
	}

	info = &FuncInfo{
		name: name, minArgs: minArgs, maxArgs: maxArgs, functor: functor, returnType: returnType, formalParams: params,
	}
	functor.SetFunc(info)
	return info, nil
}

func (info *FuncInfo) Params() []ExprFuncParam {
	return info.formalParams
}

func (info *FuncInfo) ReturnType() string {
	return info.returnType
}

func (info *FuncInfo) ToString(opt FmtOpt) string {
	var sb strings.Builder
	if len(info.Name()) == 0 {
		sb.WriteString("func")
	} else {
		sb.WriteString(info.Name())
	}
	sb.WriteByte('(')
	if info.formalParams != nil {
		for i, p := range info.formalParams {
			if i > 0 {
				sb.WriteString(", ")
			}
			sb.WriteString(p.Name())

			if p.IsDefault() {
				sb.WriteByte('=')
				if s, ok := p.DefaultValue().(string); ok {
					sb.WriteByte('"')
					sb.WriteString(s)
					sb.WriteByte('"')
				} else {
					sb.WriteString(fmt.Sprintf("%v", p.DefaultValue()))
				}
			}
		}
	}
	if info.maxArgs < 0 {
		sb.WriteString(" ...")
	}
	sb.WriteString("):")
	if len(info.returnType) > 0 {
		sb.WriteString(info.returnType)
	} else {
		sb.WriteString(TypeAny)
	}
	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 (info *FuncInfo) AllocContext(parentCtx ExprContext) (ctx ExprContext) {
	if defCtx := info.functor.GetDefinitionContext(); defCtx != nil {
		ctx = defCtx.Clone()
		ctx.SetParent(defCtx)
	} else {
		ctx = parentCtx.Clone()
		ctx.SetParent(parentCtx)
	}
	return
}

func (info *FuncInfo) ParamSpec(paramName string) ExprFuncParam {
	for _, spec := range info.formalParams {
		if spec.Name() == paramName {
			return spec
		}
	}
	return nil
}

func (info *FuncInfo) PrepareCall(name string, actualParams map[string]any) (err error) {
	passedCount := len(actualParams)
	if info.MinArgs() > passedCount {
		err = ErrTooFewParams(name, info.MinArgs(), info.MaxArgs(), passedCount)
		return
	}

	if passedCount < len(info.formalParams) {
		for _, p := range info.formalParams {
			if _, exists := actualParams[p.Name()]; !exists {
				if !p.IsDefault() {
					break
				}
				if p.IsRepeat() {
					varArgs := make([]any, 1)
					varArgs[0] = p.DefaultValue()
					actualParams[p.Name()] = varArgs
				} else {
					actualParams[p.Name()] = p.DefaultValue()
				}
			}
		}
	}

	if info.MaxArgs() >= 0 && info.MaxArgs() < len(actualParams) {
		err = ErrTooManyParams(name, info.MaxArgs(), len(actualParams))
	}
	return
}