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// 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 docserver

import (
    "fmt"
    "io/ioutil"
    "net/http"
    "path/filepath"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/crypto"
)

type DocServer struct {
    *http.Transport
    DocRoot string
    schemes []string
}

func New(docRoot string) (self *DocServer) {
    self = &DocServer{
        Transport: &http.Transport{},
        DocRoot:   docRoot,
        schemes:   []string{"file"},
    }
    self.RegisterProtocol("file", http.NewFileTransport(http.Dir(self.DocRoot)))
    return
}

// Clients should be reused instead of created as needed. Clients are safe for concurrent use by multiple goroutines.

// A Client is higher-level than a RoundTripper (such as Transport) and additionally handles HTTP details such as cookies and redirects.

func (self *DocServer) Client() *http.Client {
    return &http.Client{
        Transport: self,
    }
}

func (self *DocServer) RegisterScheme(scheme string, rt http.RoundTripper) {
    self.schemes = append(self.schemes, scheme)
    self.RegisterProtocol(scheme, rt)
}

func (self *DocServer) HasScheme(scheme string) bool {
    for _, s := range self.schemes {
        if s == scheme {
            return true
        }
    }
    return false
}

func (self *DocServer) GetAuthContent(uri string, hash common.Hash) (content []byte, err error) {
    // retrieve content
    content, err = self.Get(uri, "")
    if err != nil {
        return
    }

    // check hash to authenticate content
    chash := crypto.Sha3Hash(content)
    if chash != hash {
        content = nil
        err = fmt.Errorf("content hash mismatch %x != %x (exp)", hash[:], chash[:])
    }

    return

}

// Get(uri, path) downloads the document at uri, if path is non-empty it
// is interpreted as a filepath to which the contents are saved
func (self *DocServer) Get(uri, path string) (content []byte, err error) {
    // retrieve content
    resp, err := self.Client().Get(uri)

    defer func() {
        if resp != nil {
            resp.Body.Close()
        }
    }()
    if err != nil {
        return
    }
    content, err = ioutil.ReadAll(resp.Body)
    if err != nil {
        return
    }

    if path != "" {
        var abspath string
        abspath, err = filepath.Abs(path)
        ioutil.WriteFile(abspath, content, 0700)
    }

    return

}