package xirc

func casemapNone(name string) string {
	return name
}

// CasemapASCII of name is the canonical representation of name according to the
// ascii casemapping.
func casemapASCII(name string) string {
	nameBytes := []byte(name)
	for i, r := range nameBytes {
		if 'A' <= r && r <= 'Z' {
			nameBytes[i] = r + 'a' - 'A'
		}
	}
	return string(nameBytes)
}

// casemapRFC1459 of name is the canonical representation of name according to the
// rfc1459 casemapping.
func casemapRFC1459(name string) string {
	nameBytes := []byte(name)
	for i, r := range nameBytes {
		if 'A' <= r && r <= 'Z' {
			nameBytes[i] = r + 'a' - 'A'
		} else if r == '{' {
			nameBytes[i] = '['
		} else if r == '}' {
			nameBytes[i] = ']'
		} else if r == '\\' {
			nameBytes[i] = '|'
		} else if r == '~' {
			nameBytes[i] = '^'
		}
	}
	return string(nameBytes)
}

// casemapRFC1459Strict of name is the canonical representation of name
// according to the rfc1459-strict casemapping.
func casemapRFC1459Strict(name string) string {
	nameBytes := []byte(name)
	for i, r := range nameBytes {
		if 'A' <= r && r <= 'Z' {
			nameBytes[i] = r + 'a' - 'A'
		} else if r == '{' {
			nameBytes[i] = '['
		} else if r == '}' {
			nameBytes[i] = ']'
		} else if r == '\\' {
			nameBytes[i] = '|'
		}
	}
	return string(nameBytes)
}

type CaseMapping func(string) string

var (
	CaseMappingNone          CaseMapping = casemapNone
	CaseMappingASCII         CaseMapping = casemapASCII
	CaseMappingRFC1459       CaseMapping = casemapRFC1459
	CaseMappingRFC1459Strict CaseMapping = casemapRFC1459Strict
)

func ParseCaseMapping(s string) CaseMapping {
	var cm CaseMapping
	switch s {
	case "ascii":
		cm = CaseMappingASCII
	case "rfc1459":
		cm = CaseMappingRFC1459
	case "rfc1459-strict":
		cm = CaseMappingRFC1459Strict
	}
	return cm
}