package repo

import (
	"encoding/xml"
	"io"
	"io/ioutil"
)

// Manifest is the root element of the file.
//
// The order of the fields in this struct is the order they will be written by
// xml.Marshal.
//
// Some fields of Manifest and its children have been omitted. For full documentation of
// the Repo manifest structure, see: go/repo-manifests-explained.
type Manifest struct {
	XMLName xml.Name  `xml:"manifest"`
	Comment string    `xml:",comment"`
	Remote  []Remote  `xml:"remote"`
	Default Default   `xml:"default"`
	Project []Project `xml:"project"`
}

// Default holds default values for Project element attributes.
//
// The revision attribute is represented by `Branch` instead of `Revision` because the
// value is always a branch name. "revision" is a misnomer in the Repo manifest schema.
type Default struct {
	// Name of a Git branch (e.g. master or refs/heads/master). Project elements lacking
	// their own revision attribute will use this value.
	Branch string `xml:"revision,attr,omitempty"`

	// Name of a previously defined remote element. Project elements lacking a remote
	// attribute of their own will use this remote.
	Remote string `xml:"remote,attr,omitempty"`
}

// Remote specifies a Git URL and review server shared by one or more repos.
type Remote struct {
	// A short name unique to this manifest file. The name specified here is used as the
	// remote name in each project's .git/config, and is therefore automatically available
	// to commands like git fetch, git remote, git pull and git push.
	Name string `xml:"name,attr,omitempty"`

	// The Git URL prefix for all projects which use this remote. Each project's name is
	// appended to this prefix to form the actual URL used to clone the project.
	Fetch string `xml:"fetch,attr,omitempty"`

	// Hostname of the Gerrit server where reviews are uploaded to by repo upload. This
	// attribute is optional; if not specified then repo upload will not function.
	Review string `xml:"review,attr,omitempty"`

	// Revision omitted; Project elements will contain a revision if necessary.
}

// Project represents a single Git repository
type Project struct {
	// Name is the name of this project.
	Name string `xml:"name,attr,omitempty"`

	// Path is an optional path relative to the top directory of the repo client where the
	// Git working directory for this project should be placed. If not supplied the
	// project name is used. If the project has a parent element, its path will be
	// prefixed by the parent's.
	Path string `xml:"path,attr,omitempty"`

	// Remote is the name of a previously defined remote element. If not supplied the
	// remote given by the default element is used.
	Remote string `xml:"remote,attr,omitempty"`

	// Revision is the name of the Git branch the manifest wants to track for this
	// project. Names can be relative to refs/heads (e.g. just master) or absolute (e.g.
	// refs/heads/master). Tags and/or explicit SHA-1s should work in theory, but have not
	// been extensively tested. If not supplied the revision given by the remote element
	// is used if applicable, else the default element is used.
	Revision string `xml:"revision,attr,omitempty"`
}

// ParseManifest parses a Manifest from the given io.Reader.
func ParseManifest(r io.Reader, into *Manifest) error {
	bytes, err := ioutil.ReadAll(r)
	if err != nil {
		return err
	}
	return xml.Unmarshal(bytes, into)
}

// WriteManifest writes the given Manifest to the given io.Writer.
func WriteManifest(w io.Writer, m *Manifest) error {
	bytes, err := xml.MarshalIndent(m, "", "  ")
	if err != nil {
		return err
	}
	if _, err := w.Write([]byte(xml.Header)); err != nil {
		return err
	}
	if _, err := w.Write(bytes); err != nil {
		return err
	}
	return nil
}