package cors

import (
	"strconv"
	"strings"
)

type CORS map[string]string

// NewCors 创建一个跨域头配置
func NewCors() CORS {
	c := make(CORS)
	// 允许访问的域
	c["Access-Control-Allow-Origin"] = "*"
	// 允许跨域请求的方法
	c["Access-Control-Allow-Methods"] = "GET, POST, PUT, DELETE, OPTIONS"
	// 允许的所有头信息字段，不限于浏览器在"预检"中请求的字段
	c["Access-Control-Allow-Headers"] = "*"
	// 允许将对请求的响应暴露给页面
	c["Access-Control-Allow-Credentials"] = "false"
	// 可选，用来指定本次预检请求的有效期，单位为秒，即在此期间，不用发出另一条预检请求
	c["Access-Control-Max-Age"] = "1728000"
	return c
}

func (own CORS) AllowCredentials() CORS {
	own["Access-Control-Allow-Credentials"] = "true"
	return own
}

func (own CORS) SetMaxAge(expire int) CORS {
	own["Access-Control-Max-Age"] = strconv.Itoa(expire)
	return own
}

func (own CORS) AllowOrigins(origins ...string) CORS {
	if len(origins) == 0 {
		return own
	}
	return own.modify("Access-Control-Allow-Origin", origins...)
}

func (own CORS) AllowMethods(methods ...string) CORS {
	if len(methods) == 0 {
		return own
	}
	return own.modify("Access-Control-Allow-Methods", methods...)
}

func (own CORS) AllowHeaders(headers ...string) CORS {
	if len(headers) == 0 {
		return own
	}
	return own.modify("Access-Control-Allow-Methods", headers...)
}

func (own CORS) ExposeHeaders(headers ...string) CORS {
	if len(headers) == 0 {
		return own
	}
	return own.modify("Access-Control-Expose-Headers", headers...)
}

func (own CORS) modify(field string, values ...string) CORS {
	var builder strings.Builder
	for _, v := range values {
		builder.WriteString(v)
		builder.WriteString(", ")
	}
	s := builder.String()
	own[field] = s[:len(s)-2]
	builder.Reset()
	return own
}