package crumbs

import (
    "encoding"
    "fmt"
)

type pointertype[T any] interface{
    *T
    encoding.TextUnmarshaler
}

// Parse provides a convenience wrapper around an encoding.TextUnmarshaler.
//
// UM is expected to be the pointer type of T and satisfy encoding.TextUnmarshaler.
//
// Common invocation ("crumbs.Parse[S]" even though "*S" is the UnmarshalText receiver:
//   type S struct{Text string}
//   func (s *S) UnmarshalText(text []byte) error {
//       *s = string(text); return nil
//   }
//  
//   s, err := crumbs.Parse[S]
func Parse[T any, UM pointertype[T]](text []byte) (*T, error) {
    var v UM = new(T)
    err := v.UnmarshalText(text)
    if err != nil {
        return nil, err
    }

    return v, nil
}

func ParseDereference[T any, UM pointertype[T]](text []byte) (T, error) {
    v, err := Parse[T, UM](text)
    if err != nil {
        return *new(T), err
    } else if v == nil {
        panic(fmt.Sprintf("internal/crumbs: ParseDereference[T=%T](%q): nil", *new(T), text))
    }

    return *v, nil
}

// ParseString is a convenience wrapper around [Parse]
// for parsing from "string" as opposed to "[]byte".
func ParseString[T any, UM pointertype[T]](text string) (*T, error) {
    return Parse[T, UM]([]byte(text))
}

func MustParseString[T any, UM pointertype[T]](text string) *T {
    v, err := Parse[T, UM]([]byte(text))
    if err != nil {
        panic(fmt.Sprintf("internal/crumbs: MustParseStringDereference[T=%T](%q): %v", *new(T), text, err))
    }

    return v
}

// ParseString is a convenience wrapper around [Parse]
// for parsing from "string" as opposed to "[]byte".
func ParseStringDereference[T any, UM pointertype[T]](text string) (T, error) {
    v, err := Parse[T, UM]([]byte(text))
    if err != nil {
        return *new(T), err
    } else if v == nil {
        panic(fmt.Sprintf("internal/crumbs: ParseStringDereference[T=%T](%q): nil", *new(T), text))
    }

    return *v, nil
}

func MustParseStringDereference[T any, UM pointertype[T]](text string) T {
    v, err := Parse[T, UM]([]byte(text))
    if err != nil {
        panic(fmt.Sprintf("internal/crumbs: MustParseStringDereference[T=%T](%q): %v", *new(T), text, err))
    } else if v == nil {
        panic(fmt.Sprintf("internal/crumbs: MustParseStringDereference[T=%T](%q): nil", *new(T), text))
    }

    return *v
}