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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// This test tests some internals of the flate package.
// The tests in package compress/gzip serve as the
// end-to-end test of the decompressor.

package flate

import (
        "bytes"
        "reflect"
        "testing"
)

// The Huffman code lengths used by the fixed-format Huffman blocks.
var fixedHuffmanBits = [...]int{
        // 0-143 length 8
        8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
        8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
        8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
        8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
        8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
        8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
        8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
        8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
        8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,

        // 144-255 length 9
        9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
        9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
        9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
        9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
        9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
        9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
        9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,

        // 256-279 length 7
        7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
        7, 7, 7, 7, 7, 7, 7, 7,

        // 280-287 length 8
        8, 8, 8, 8, 8, 8, 8, 8,
}

type InitDecoderTest struct {
        in  []int
        out huffmanDecoder
        ok  bool
}

var initDecoderTests = []*InitDecoderTest{
        // Example from Connell 1973,
        {
                []int{3, 5, 2, 4, 3, 5, 5, 4, 4, 3, 4, 5},
                huffmanDecoder{
                        2, 5,
                        [maxCodeLen + 1]int{2: 0, 4, 13, 31},
                        [maxCodeLen + 1]int{2: 0, 1, 6, 20},
                        // Paper used different code assignment:
                        // 2, 9, 4, 0, 10, 8, 3, 7, 1, 5, 11, 6
                        // Reordered here so that codes of same length
                        // are assigned to increasing numbers.
                        []int{2, 0, 4, 9, 3, 7, 8, 10, 1, 5, 6, 11},
                },
                true,
        },

        // Example from RFC 1951 section 3.2.2
        {
                []int{2, 1, 3, 3},
                huffmanDecoder{
                        1, 3,
                        [maxCodeLen + 1]int{1: 0, 2, 7},
                        [maxCodeLen + 1]int{1: 0, 1, 4},
                        []int{1, 0, 2, 3},
                },
                true,
        },

        // Second example from RFC 1951 section 3.2.2
        {
                []int{3, 3, 3, 3, 3, 2, 4, 4},
                huffmanDecoder{
                        2, 4,
                        [maxCodeLen + 1]int{2: 0, 6, 15},
                        [maxCodeLen + 1]int{2: 0, 1, 8},
                        []int{5, 0, 1, 2, 3, 4, 6, 7},
                },
                true,
        },

        // Static Huffman codes (RFC 1951 section 3.2.6)
        {
                fixedHuffmanBits[0:],
                fixedHuffmanDecoder,
                true,
        },

        // Illegal input.
        {
                []int{},
                huffmanDecoder{},
                false,
        },

        // Illegal input.
        {
                []int{0, 0, 0, 0, 0, 0, 0},
                huffmanDecoder{},
                false,
        },
}

func TestInitDecoder(t *testing.T) {
        for i, tt := range initDecoderTests {
                var h huffmanDecoder
                if h.init(tt.in) != tt.ok {
                        t.Errorf("test %d: init = %v", i, !tt.ok)
                        continue
                }
                if !reflect.DeepEqual(&h, &tt.out) {
                        t.Errorf("test %d:\nhave %v\nwant %v", i, h, tt.out)
                }
        }
}

func TestUncompressedSource(t *testing.T) {
        decoder := NewReader(bytes.NewBuffer([]byte{0x01, 0x01, 0x00, 0xfe, 0xff, 0x11}))
        output := make([]byte, 1)
        n, error := decoder.Read(output)
        if n != 1 || error != nil {
                t.Fatalf("decoder.Read() = %d, %v, want 1, nil", n, error)
        }
        if output[0] != 0x11 {
                t.Errorf("output[0] = %x, want 0x11", output[0])
        }
}