// Copyright (c) 2025, Christian Lee Seibold
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its
//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

package main

import (
	"bytes"
	"fmt"
	"os"
	"path"
	"sort"
	"time"

	"github.com/klauspost/compress/zstd"
)

type TreeObject struct {
	hash    Hash
	entries []TreeEntry
}

func DecodeTree(vcsDirectory string, hash Hash) TreeObject {
	file_contents, err := os.ReadFile(path.Join(vcsDirectory, "objects", hash.HexString()))
	if err != nil {
		return TreeObject{}
	}
	zr, _ := zstd.NewReader(bytes.NewReader(file_contents))
	result := new(bytes.Buffer)
	result.ReadFrom(zr)
	zr.Close()

	_, contents, _ := bytes.Cut(result.Bytes(), []byte{00})

	entries := []TreeEntry{}
	reader := bytes.NewReader(contents)

	for {
		entry := ParseTreeEntry(reader)
		if (entry != TreeEntry{}) {
			entries = append(entries, entry)
		} else {
			break
		}
	}

	return TreeObject{hash, entries}
}

func (t TreeObject) FindEntryName(name string) TreeEntry {
	for _, entry := range t.entries {
		if entry.name == name {
			return entry
		}
	}

	return TreeEntry{}
}

func (t TreeObject) Encode() []byte {
	sort.SliceStable(t.entries, func(i, j int) bool {
		return caseInsensitiveStringCompare(t.entries[i].name, t.entries[j].name) == -1
	})

	buf := bytes.Buffer{}
	for _, entry := range t.entries {
		buf.Write(entry.Encode())
	}

	return buf.Bytes()
}

func (t TreeObject) ToIndex(modTime time.Time) *Index {
	newIndex := make(Index)
	for _, entry := range t.entries {
		if entry.t == "blob" {
			newIndex[entry.name] = IndexEntry{"c", "100644", entry.name, entry.hash, modTime}
		} else if entry.t == "tree" {
			// TODO
		}
	}

	return &newIndex
}

type TreeEntry struct {
	t    string // blob or tree
	hash Hash
	name string
}

func ParseTreeEntry(reader *bytes.Reader) TreeEntry {
	// Get next space character to get the mode
	modebuf := bytes.Buffer{}
	for {
		b, err := reader.ReadByte()
		if err != nil {
			return TreeEntry{}
		}
		if b == ' ' {
			break
		}
		modebuf.WriteByte(b)
	}

	// Read until NUL character into name
	name := bytes.Buffer{}
	for {
		b, err := reader.ReadByte()
		if err != nil {
			return TreeEntry{}
		}
		if b == 0 {
			break
		}
		name.WriteByte(b)
	}

	// Create array for the hash
	var h Hash
	_, err := reader.Read(h[:])
	if err != nil {
		return TreeEntry{}
	}

	// Create tree entry based on mode
	mode := modebuf.String()
	entryType := "blob"
	if mode != "100644" {
		entryType = "tree"
	}

	return TreeEntry{entryType, h, name.String()}
}

func (te TreeEntry) Encode() []byte {
	mode := ""
	if te.t == "blob" {
		mode = "100644" // Default mode for blobs
	}
	buf := bytes.Buffer{}
	buf.WriteString(fmt.Sprintf("%s %s\000", mode, te.name))
	buf.Write(te.hash[:])
	return buf.Bytes()
}