// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package trie

import (
	"bytes"
	"fmt"

	"github.com/ethereum/go-ethereum/ethdb"
	"github.com/ethereum/go-ethereum/log"
	"github.com/ethereum/go-ethereum/trie"
)

var VerifyProof = trie.VerifyProof
var VerifyRangeProof = trie.VerifyRangeProof

// Prove constructs a merkle proof for key. The result contains all encoded nodes
// on the path to the value at key. The value itself is also included in the last
// node and can be retrieved by verifying the proof.
//
// If the trie does not contain a value for key, the returned proof contains all
// nodes of the longest existing prefix of the key (at least the root node), ending
// with the node that proves the absence of the key.
func (t *Trie) Prove(key []byte, fromLevel uint, proofDb ethdb.KeyValueWriter) error {
	// Collect all nodes on the path to key.
	var (
		prefix []byte
		nodes  []node
		tn     = t.root
	)
	key = keybytesToHex(key)
	for len(key) > 0 && tn != nil {
		switch n := tn.(type) {
		case *shortNode:
			if len(key) < len(n.Key) || !bytes.Equal(n.Key, key[:len(n.Key)]) {
				// The trie doesn't contain the key.
				tn = nil
			} else {
				tn = n.Val
				prefix = append(prefix, n.Key...)
				key = key[len(n.Key):]
			}
			nodes = append(nodes, n)
		case *fullNode:
			tn = n.Children[key[0]]
			prefix = append(prefix, key[0])
			key = key[1:]
			nodes = append(nodes, n)
		case hashNode:
			var err error
			tn, err = t.resolveHash(n, prefix)
			if err != nil {
				log.Error(fmt.Sprintf("Unhandled trie error: %v", err))
				return err
			}
		default:
			panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
		}
	}
	hasher := newHasher(false)
	defer returnHasherToPool(hasher)

	for i, n := range nodes {
		if fromLevel > 0 {
			fromLevel--
			continue
		}
		var hn node
		n, hn = hasher.proofHash(n)
		if hash, ok := hn.(hashNode); ok || i == 0 {
			// If the node's database encoding is a hash (or is the
			// root node), it becomes a proof element.
			enc := nodeToBytes(n)
			if !ok {
				hash = hasher.hashData(enc)
			}
			proofDb.Put(hash, enc)
		}
	}
	return nil
}

// Prove constructs a merkle proof for key. The result contains all encoded nodes
// on the path to the value at key. The value itself is also included in the last
// node and can be retrieved by verifying the proof.
//
// If the trie does not contain a value for key, the returned proof contains all
// nodes of the longest existing prefix of the key (at least the root node), ending
// with the node that proves the absence of the key.
func (t *StateTrie) Prove(key []byte, fromLevel uint, proofDb ethdb.KeyValueWriter) error {
	return t.trie.Prove(key, fromLevel, proofDb)
}