// In this example, a parser is created that is able to parse input that looks
// like "Hello, <name>!", and that extracts the name from it.
//
// The implementation uses only parser/combinator TokenHandler functions and does
// not implement a full-fledged state-based Parser for it. If you want to see the
// same kind of functionality, implementated using a Parser, take a look at the
// other hello examples.
package examples

import (
	"fmt"

	"git.makaay.nl/mauricem/go-parsekit"
)

func Example_helloWorldUsingTokenizer() {
	parser := createHelloTokenizer()

	for i, input := range []string{
		"Hello, world!",
		"HELLO ,Johnny!",
		"hello , Bob123!",
		"hello Pizza!",
		"Oh no!",
		"Hello, world",
		"Hello,!",
	} {
		output, err := parser.Execute(input)
		if err != nil {
			fmt.Printf("[%d] Input: %q Error: %s\n", i, input, err.Full())
		} else {
			fmt.Printf("[%d] Input: %q Output: %s\n", i, input, output)
		}
	}
	// Output:
	// [0] Input: "Hello, world!" Output: world
	// [1] Input: "HELLO ,Johnny!" Output: Johnny
	// [2] Input: "hello , Bob123!" Output: Bob123
	// [3] Input: "hello Pizza!" Output: Pizza
	// [4] Input: "Oh no!" Error: unexpected input (expected a friendly greeting) at start of file
	// [5] Input: "Hello, world" Error: unexpected input (expected a friendly greeting) at start of file
	// [6] Input: "Hello,!" Error: unexpected input (expected a friendly greeting) at start of file
}

// ---------------------------------------------------------------------------
// Implementation of the parser
// ---------------------------------------------------------------------------

func createHelloTokenizer() *parsekit.Tokenizer {
	// Easy access to parsekit definition.
	c, a, m := parsekit.C, parsekit.A, parsekit.M

	// Using the parser/combinator support of parsekit, we create a TokenHandler function
	// that does all the work. The 'greeting' TokenHandler matches the whole input and
	// drops all but the name from it.
	hello := a.StrNoCase("hello")
	comma := c.Seq(c.Opt(a.Whitespace), a.Comma, c.Opt(a.Whitespace))
	separator := c.Any(comma, a.Whitespace)
	name := c.OneOrMore(c.Not(a.Excl))
	greeting := c.Seq(m.Drop(hello), m.Drop(separator), name, m.Drop(a.Excl), a.EndOfFile)

	// Create a Tokenizer that wraps the 'greeting' TokenHandler and allows
	// us to match some input against that handler.
	return parsekit.NewTokenizer(greeting)
}