package reader_test

import (
	"bufio"
	"fmt"
	"io"
	"strings"
	"testing"

	"git.makaay.nl/mauricem/go-parsekit/reader"
	"github.com/stretchr/testify/assert"
)

func ExampleNew() {
	r := reader.New(strings.NewReader("Hello, world!"))
	at := func(i int) rune { r, _ := r.RuneAt(i); return r }

	fmt.Printf("%c", at(0))
	fmt.Printf("%c", at(12))

	// Output:
	// H!
}

func TestNew_VariousInputTypesCanBeUsed(t *testing.T) {
	for _, test := range []struct {
		name  string
		input interface{}
	}{
		{"string", "Hello, world!"},
		{"io.Reader", strings.NewReader("Hello, world!")},
		{"*bufio.Reader", bufio.NewReader(strings.NewReader("Hello, world!"))},
		{"bufio.Reader", *(bufio.NewReader(strings.NewReader("Hello, world!")))},
	} {
		r := reader.New(test.input)
		firstRune, _ := r.RuneAt(0)
		if firstRune != 'H' {
			t.Errorf("[%s] first rune not 'H'", test.name)
		}
		lastRune, _ := r.RuneAt(12)
		if lastRune != '!' {
			t.Errorf("[%s] last rune not '!'", test.name)
		}
	}
}

func TestNew_UnhandledInputType_Panics(t *testing.T) {
	assert.PanicsWithValue(t,
		"parsekit.reader.New(): no support for input of type int",
		func() { reader.New(12345) })
}

func TestReader_RuneAt(t *testing.T) {
	r := reader.New(strings.NewReader("Hello, world!"))
	at := func(i int) rune { r, _ := r.RuneAt(i); return r }

	// It is possible to go back and forth while reading the input.
	result := fmt.Sprintf("%c%c%c%c", at(0), at(12), at(7), at(0))
	assert.Equal(t, "H!wH", result)
}

func TestReader_RuneAt_endOfFile(t *testing.T) {
	r := reader.New(strings.NewReader("Hello, world!"))

	rn, err := r.RuneAt(13)
	result := fmt.Sprintf("%q %s %t", rn, err, err == io.EOF)
	assert.Equal(t, "'�' EOF true", result)

	rn, err = r.RuneAt(20)
	result = fmt.Sprintf("%q %s %t", rn, err, err == io.EOF)
	assert.Equal(t, "'�' EOF true", result)
}

func TestReader_RuneAt_invalidRune(t *testing.T) {
	r := reader.New(strings.NewReader("Hello, \xcdworld!"))
	at := func(i int) rune { r, _ := r.RuneAt(i); return r }

	result := fmt.Sprintf("%c%c%c%c", at(6), at(7), at(8), at(9))
	assert.Equal(t, " �wo", result, "result")
}

func ExampleReader_RuneAt() {
	reader := reader.New(strings.NewReader("Hello, world!"))

	fmt.Printf("Runes: ")
	for i := 0; ; i++ {
		r, err := reader.RuneAt(i)
		if err != nil {
			fmt.Printf("\nErr: %s\n", err)
			break
		}
		fmt.Printf("%c", r)
	}

	// Output:
	// Runes: Hello, world!
	// Err: EOF
}

func TestRuneAt_SkipsBOMAtStartOfFile(t *testing.T) {
	r := reader.New(strings.NewReader("\uFEFFBommetje!"))
	b, _ := r.RuneAt(0)
	o, _ := r.RuneAt(1)
	m, _ := r.RuneAt(2)
	bom := fmt.Sprintf("%c%c%c", b, o, m)
	assert.Equal(t, "Bom", bom, "first three runes")
}

func TestReader_Flush(t *testing.T) {
	r := reader.New(strings.NewReader("Hello, world!"))
	at := func(i int) rune { r, _ := r.RuneAt(i); return r }

	// Fills the buffer with the first 8 runes on the input: "Hello, w"
	result := fmt.Sprintf("%c", at(7))
	assert.Equal(t, "w", result, "first read")

	// Now flush the first 4 runes from the buffer (dropping "Hell" from it)
	r.Flush(4)

	// Rune 0 is now pointing at what originally was rune offset 4.
	// We can continue reading from there.
	result = fmt.Sprintf("%c%c%c%c%c%c", at(0), at(1), at(2), at(3), at(4), at(5))
	assert.Equal(t, "o, wor", result)
}

func ExampleReader_Flush() {
	r := reader.New(strings.NewReader("dog eat dog!"))
	at := func(offset int) rune { c, _ := r.RuneAt(offset); return c }

	// Read from the first 4 runes of the input.
	fmt.Printf("%c%c%c%c", at(0), at(1), at(2), at(3))

	// Flush those 4 runes, bringing offset 0 to the start of "eat dog".
	r.Flush(4)

	// Read another 4 runes, because of the flushing, we start at offset 0.
	fmt.Printf("%c%c%c%c", at(1), at(2), at(0), at(3))

	// Again, flush 4 runes, bringing offset 0 to the start of "dog!".
	r.Flush(4)

	// Read from the remainder runes.
	fmt.Printf("%c%c%c%c%c", at(2), at(1), at(1), at(0), at(3))

	// Output:
	// dog ate good!
}

func TestGivenNumberOfRunesTooHigh_Flush_Panics(t *testing.T) {
	r := reader.New(strings.NewReader("Hello, world!"))

	// Fill buffer with "Hello, worl", the first 11 runes.
	r.RuneAt(10)

	// However, we flush 12 runes, which exceeds the buffer size.
	assert.PanicsWithValue(t,
		"parsekit.Input.Reader.Flush(): number of runes to flush "+
			"(12) exceeds size of the buffer (11)",
		func() { r.Flush(12) })
}