package resource

// Quantity is a fixed-point representation of a number. It
// provides convenient marshaling/unmarshaling in JSON and YAML,
// in addition to String() and AsInt64() accessors.
//
// The serialization format is:
//
// ``` <quantity> ::= <signedNumber><suffix>
//
// (Note that <suffix> may be empty, from the "" case in
// <decimalSI>.)
//
// <digit> ::= 0 | 1 | ... | 9 <digits> ::= <digit> |
// <digit><digits> <number> ::= <digits> | <digits>.<digits> |
// <digits>. | .<digits> <sign> ::= "+" | "-" <signedNumber> ::=
// <number> | <sign><number> <suffix> ::= <binarySI> |
// <decimalExponent> | <decimalSI> <binarySI> ::= Ki | Mi | Gi |
// Ti | Pi | Ei
//
// (International System of units; See:
// http://physics.nist.gov/cuu/Units/binary.html)
//
// <decimalSI> ::= m | "" | k | M | G | T | P | E
//
// (Note that 1024 = 1Ki but 1000 = 1k; I didn't choose the
// capitalization.)
//
// <decimalExponent> ::= "e" <signedNumber> | "E" <signedNumber>
// ```
//
// No matter which of the three exponent forms is used, no
// quantity may represent a number greater than 2^63-1 in
// magnitude, nor may it have more than 3 decimal places. Numbers
// larger or more precise will be capped or rounded up. (E.g.:
// 0.1m will rounded up to 1m.) This may be extended in the
// future if we require larger or smaller quantities.
//
// When a Quantity is parsed from a string, it will remember the
// type of suffix it had, and will use the same type again when
// it is serialized.
//
// Before serializing, Quantity will be put in "canonical form".
// This means that Exponent/suffix will be adjusted up or down
// (with a corresponding increase or decrease in Mantissa) such
// that:
//
// - No precision is lost - No fractional digits will be emitted -
// The exponent (or suffix) is as large as possible.
//
// The sign will be omitted unless the number is negative.
//
// Examples:
//
// - 1.5 will be serialized as "1500m" - 1.5Gi will be serialized
// as "1536Mi"
//
// Note that the quantity will NEVER be internally represented by
// a floating point number. That is the whole point of this
// exercise.
//
// Non-canonical values will still parse as long as they are well
// formed, but will be re-emitted in their canonical form. (So
// always use canonical form, or don't diff.)
//
// This format is intended to make it difficult to use these
// numbers without writing some sort of special handling code in
// the hopes that that will cause implementors to also use a
// fixed point implementation.
#Quantity: number | string