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// Copyright 2011 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.

package x509

import (
        "encoding/pem"
)

// CertPool is a set of certificates.
type CertPool struct {
        bySubjectKeyId map[string][]int
        byName         map[string][]int
        certs          []*Certificate
}

// NewCertPool returns a new, empty CertPool.
func NewCertPool() *CertPool {
        return &CertPool{
                make(map[string][]int),
                make(map[string][]int),
                nil,
        }
}

// findVerifiedParents attempts to find certificates in s which have signed the
// given certificate. If no such certificate can be found or the signature
// doesn't match, it returns nil.
func (s *CertPool) findVerifiedParents(cert *Certificate) (parents []int) {
        if s == nil {
                return
        }
        var candidates []int

        if len(cert.AuthorityKeyId) > 0 {
                candidates = s.bySubjectKeyId[string(cert.AuthorityKeyId)]
        }
        if len(candidates) == 0 {
                candidates = s.byName[string(cert.RawIssuer)]
        }

        for _, c := range candidates {
                if cert.CheckSignatureFrom(s.certs[c]) == nil {
                        parents = append(parents, c)
                }
        }

        return
}

// AddCert adds a certificate to a pool.
func (s *CertPool) AddCert(cert *Certificate) {
        if cert == nil {
                panic("adding nil Certificate to CertPool")
        }

        // Check that the certificate isn't being added twice.
        for _, c := range s.certs {
                if c.Equal(cert) {
                        return
                }
        }

        n := len(s.certs)
        s.certs = append(s.certs, cert)

        if len(cert.SubjectKeyId) > 0 {
                keyId := string(cert.SubjectKeyId)
                s.bySubjectKeyId[keyId] = append(s.bySubjectKeyId[keyId], n)
        }
        name := string(cert.RawSubject)
        s.byName[name] = append(s.byName[name], n)
}

// AppendCertsFromPEM attempts to parse a series of PEM encoded certificates.
// It appends any certificates found to s and returns true if any certificates
// were successfully parsed.
//
// On many Linux systems, /etc/ssl/cert.pem will contain the system wide set
// of root CAs in a format suitable for this function.
func (s *CertPool) AppendCertsFromPEM(pemCerts []byte) (ok bool) {
        for len(pemCerts) > 0 {
                var block *pem.Block
                block, pemCerts = pem.Decode(pemCerts)
                if block == nil {
                        break
                }
                if block.Type != "CERTIFICATE" || len(block.Headers) != 0 {
                        continue
                }

                cert, err := ParseCertificate(block.Bytes)
                if err != nil {
                        continue
                }

                s.AddCert(cert)
                ok = true
        }

        return
}

// Subjects returns a list of the DER-encoded subjects of
// all of the certificates in the pool. 
func (s *CertPool) Subjects() (res [][]byte) {
        res = make([][]byte, len(s.certs))
        for i, c := range s.certs {
                res[i] = c.RawSubject
        }
        return
}