package redcon

import (
	"strconv"
)

// Type of RESP
type Type byte

// Various RESP kinds
const (
	Integer = ':'
	String  = '+'
	Bulk    = '$'
	Array   = '*'
	Error   = '-'
)

// RESP ...
type RESP struct {
	Type  Type
	Raw   []byte
	Data  []byte
	Count int
}

// ForEach iterates over each Array element
func (r *RESP) ForEach(iter func(resp RESP) bool) {
	data := r.Data
	for i := 0; i < r.Count; i++ {
		n, resp := ReadNextRESP(data)
		if !iter(resp) {
			return
		}
		data = data[n:]
	}
}

// ReadNextRESP returns the next resp in b and returns the number of bytes the
// took up the result.
func ReadNextRESP(b []byte) (n int, resp RESP) {
	if len(b) == 0 {
		return 0, RESP{} // no data to read
	}
	resp.Type = Type(b[0])
	switch resp.Type {
	case Integer, String, Bulk, Array, Error:
	default:
		return 0, RESP{} // invalid kind
	}
	// read to end of line
	i := 1
	for ; ; i++ {
		if i == len(b) {
			return 0, RESP{} // not enough data
		}
		if b[i] == '\n' {
			if b[i-1] != '\r' {
				return 0, RESP{} //, missing CR character
			}
			i++
			break
		}
	}
	resp.Raw = b[0:i]
	resp.Data = b[1 : i-2]
	if resp.Type == Integer {
		// Integer
		if len(resp.Data) == 0 {
			return 0, RESP{} //, invalid integer
		}
		var j int
		if resp.Data[0] == '-' {
			if len(resp.Data) == 1 {
				return 0, RESP{} //, invalid integer
			}
			j++
		}
		for ; j < len(resp.Data); j++ {
			if resp.Data[j] < '0' || resp.Data[j] > '9' {
				return 0, RESP{} // invalid integer
			}
		}
		return len(resp.Raw), resp
	}
	if resp.Type == String || resp.Type == Error {
		// String, Error
		return len(resp.Raw), resp
	}
	var err error
	resp.Count, err = strconv.Atoi(string(resp.Data))
	if resp.Type == Bulk {
		// Bulk
		if err != nil {
			return 0, RESP{} // invalid number of bytes
		}
		if resp.Count < 0 {
			resp.Data = nil
			resp.Count = 0
			return len(resp.Raw), resp
		}
		if len(b) < i+resp.Count+2 {
			return 0, RESP{} // not enough data
		}
		if b[i+resp.Count] != '\r' || b[i+resp.Count+1] != '\n' {
			return 0, RESP{} // invalid end of line
		}
		resp.Data = b[i : i+resp.Count]
		resp.Raw = b[0 : i+resp.Count+2]
		resp.Count = 0
		return len(resp.Raw), resp
	}
	// Array
	if err != nil {
		return 0, RESP{} // invalid number of elements
	}
	var tn int
	sdata := b[i:]
	for j := 0; j < resp.Count; j++ {
		rn, rresp := ReadNextRESP(sdata)
		if rresp.Type == 0 {
			return 0, RESP{}
		}
		tn += rn
	}
	resp.Data = b[i : i+tn]
	resp.Raw = b[0 : i+tn]
	return len(resp.Raw), resp
}