// Mgmt
// Copyright (C) James Shubin and the project contributors
// Written by James Shubin <james@shubin.ca> and the project contributors
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
//
// Additional permission under GNU GPL version 3 section 7
//
// If you modify this program, or any covered work, by linking or combining it
// with embedded mcl code and modules (and that the embedded mcl code and
// modules which link with this program, contain a copy of their source code in
// the authoritative form) containing parts covered by the terms of any other
// license, the licensors of this program grant you additional permission to
// convey the resulting work. Furthermore, the licensors of this program grant
// the original author, James Shubin, additional permission to update this
// additional permission if he deems it necessary to achieve the goals of this
// additional permission.

package puppet

import (
	"context"
	"fmt"
	"os"
	"strings"
	"sync"
	"time"

	cliUtil "github.com/purpleidea/mgmt/cli/util"
	"github.com/purpleidea/mgmt/engine"
	"github.com/purpleidea/mgmt/gapi"
	"github.com/purpleidea/mgmt/pgraph"
	"github.com/purpleidea/mgmt/util"
	"github.com/purpleidea/mgmt/util/errwrap"
)

const (
	// Name is the name of this frontend.
	Name = "puppet"

	// PuppetFile is the entry point filename that we use. It is arbitrary.
	PuppetFile = "/file.pp"

	// PuppetConf is the entry point config filename that we use.
	PuppetConf = "/puppet.conf"

	// PuppetSite is the entry point folder that we use. It is arbitrary.
	PuppetSite = "/puppet/"
)

func init() {
	gapi.Register(Name, func() gapi.GAPI { return &GAPI{} }) // register
}

// GAPI implements the main puppet GAPI interface.
type GAPI struct {
	InputURI string

	// Mode of operation can be: agent, file, string, dir.
	Mode string

	puppetFile   string
	puppetString string
	puppetDir    string
	// The path to a dedicated puppet.conf file for mgmt.
	puppetConf  string
	data        *gapi.Data
	initialized bool
	wg          sync.WaitGroup
	err         error
}

// Cli takes an *Info struct, and returns our deploy if activated, and if there
// are any validation problems, you should return an error. If there is no
// deploy, then you should return a nil deploy and a nil error.
func (obj *GAPI) Cli(info *gapi.Info) (*gapi.Deploy, error) {
	args, ok := info.Args.(*cliUtil.PuppetArgs)
	if !ok {
		// programming error
		return nil, fmt.Errorf("could not convert to our struct")
	}

	fs := info.Fs
	writeableFS, ok := fs.(engine.WriteableFS)
	if !ok {
		return nil, fmt.Errorf("the FS was not writeable")
	}

	isDir := func(p string) (bool, error) {
		if !strings.HasPrefix(p, "/") {
			return false, nil
		}
		if !strings.HasSuffix(p, "/") {
			return false, nil
		}
		fi, err := os.Stat(p)
		if err != nil {
			return false, err
		}
		return fi.IsDir(), nil
	}

	var mode string
	if args.Input == "agent" {
		mode = "agent"

	} else if strings.HasSuffix(args.Input, ".pp") {
		mode = "file"
		if err := gapi.CopyFileToFs(writeableFS, args.Input, PuppetFile); err != nil {
			return nil, errwrap.Wrapf(err, "can't copy code from `%s` to `%s`", args.Input, PuppetFile)
		}

	} else if exists, err := isDir(args.Input); err != nil {
		return nil, errwrap.Wrapf(err, "can't read dir `%s`", args.Input)

	} else if err == nil && exists { // from the isDir result...
		// we have a whole directory of files to run
		mode = "dir"
		// TODO: this code path is untested! test and then rm this notice
		if err := gapi.CopyDirToFs(fs, args.Input, PuppetSite); err != nil {
			return nil, errwrap.Wrapf(err, "can't copy code to `%s`", PuppetSite)
		}

	} else {
		mode = "string"
		if err := gapi.CopyStringToFs(writeableFS, args.Input, PuppetFile); err != nil {
			return nil, errwrap.Wrapf(err, "can't copy code to `%s`", PuppetFile)
		}
	}

	// TODO: do we want to include this if we have mode == "dir" ?
	if args.PuppetConf != "" {
		if err := gapi.CopyFileToFs(writeableFS, args.PuppetConf, PuppetConf); err != nil {
			return nil, errwrap.Wrapf(err, "can't copy puppet conf from `%s` to '%s'", args.PuppetConf, PuppetConf)

		}
	}

	return &gapi.Deploy{
		Name: Name,
		Noop: info.Flags.Noop,
		Sema: info.Flags.Sema,
		GAPI: &GAPI{
			InputURI: fs.URI(),
			Mode:     mode,
		},
	}, nil
}

// Init initializes the puppet GAPI struct.
func (obj *GAPI) Init(data *gapi.Data) error {
	if obj.initialized {
		return fmt.Errorf("already initialized")
	}
	if obj.InputURI == "" {
		return fmt.Errorf("the InputURI param must be specified")
	}
	switch obj.Mode {
	case "agent", "file", "string", "dir":
		// pass
	default:
		return fmt.Errorf("the Mode param is invalid")
	}
	obj.data = data // store for later

	fs, err := obj.data.World.Fs(obj.InputURI) // open the remote file system
	if err != nil {
		return errwrap.Wrapf(err, "can't load data from file system `%s`", obj.InputURI)
	}

	if obj.Mode == "file" {
		b, err := fs.ReadFile(PuppetFile) // read the single file out of it
		if err != nil {
			return errwrap.Wrapf(err, "can't read code from file `%s`", PuppetFile)
		}

		// store the puppet file on disk for other binaries to see and use
		prefix := fmt.Sprintf("%s-%s-%s", data.Program, data.Hostname, strings.Replace(PuppetFile, "/", "", -1))
		tmpfile, err := os.CreateTemp("", prefix)
		if err != nil {
			return errwrap.Wrapf(err, "can't create temp file")
		}
		obj.puppetFile = tmpfile.Name() // path to temp file
		defer tmpfile.Close()
		if _, err := tmpfile.Write(b); err != nil {
			return errwrap.Wrapf(err, "can't write file")
		}

	} else if obj.Mode == "string" {
		b, err := fs.ReadFile(PuppetFile) // read the single code string out of it
		if err != nil {
			return errwrap.Wrapf(err, "can't read code from file `%s`", PuppetFile)
		}
		obj.puppetString = string(b)

	} else if obj.Mode == "dir" {
		// store the puppet files on disk for other binaries to see and use
		prefix := fmt.Sprintf("%s-%s-%s", data.Program, data.Hostname, strings.Replace(PuppetSite, "/", "", -1))
		tmpdirName, err := os.MkdirTemp("", prefix)
		if err != nil {
			return errwrap.Wrapf(err, "can't create temp dir")
		}
		if tmpdirName == "" || tmpdirName == "/" {
			return fmt.Errorf("bad tmpdir created")
		}
		obj.puppetDir = tmpdirName // path to temp dir
		// TODO: this code path is untested! test and then rm this notice
		if err := util.CopyFsToDisk(fs, PuppetSite, tmpdirName, false); err != nil {
			return errwrap.Wrapf(err, "can't copy dir")
		}
	}

	if fi, err := fs.Stat(PuppetConf); err == nil && !fi.IsDir() { // if exists?
		b, err := fs.ReadFile(PuppetConf) // read the single file out of it
		if err != nil {
			return errwrap.Wrapf(err, "can't read config from file `%s`", PuppetConf)
		}

		// store the puppet conf on disk for other binaries to see and use
		prefix := fmt.Sprintf("%s-%s-%s", data.Program, data.Hostname, strings.Replace(PuppetConf, "/", "", -1))
		tmpfile, err := os.CreateTemp("", prefix)
		if err != nil {
			return errwrap.Wrapf(err, "can't create temp file")
		}
		obj.puppetConf = tmpfile.Name() // path to temp file
		defer tmpfile.Close()
		if _, err := tmpfile.Write(b); err != nil {
			return errwrap.Wrapf(err, "can't write file")
		}
	}

	obj.initialized = true
	return nil
}

// Info returns some data about the GAPI implementation.
func (obj *GAPI) Info() *gapi.InfoResult {
	return &gapi.InfoResult{
		URI: obj.InputURI,
	}
}

// graph returns a current Graph.
func (obj *GAPI) graph() (*pgraph.Graph, error) {
	if !obj.initialized {
		return nil, fmt.Errorf("%s: GAPI is not initialized", Name)
	}
	config, err := obj.ParseConfigFromPuppet()
	if err != nil {
		return nil, err
	}
	if config == nil {
		return nil, fmt.Errorf("function ParseConfigFromPuppet returned nil")
	}
	g, err := config.NewGraphFromConfig(obj.data.Hostname, obj.data.World, obj.data.Noop)
	return g, err
}

// Next returns nil errors every time there could be a new graph.
func (obj *GAPI) Next(ctx context.Context) chan gapi.Next {
	puppetChan := func() <-chan time.Time { // helper function
		return time.Tick(time.Duration(obj.refreshInterval()) * time.Second)
	}
	ch := make(chan gapi.Next)
	obj.wg.Add(1)
	go func() {
		defer obj.cleanup()
		defer obj.wg.Done()
		defer close(ch) // this will run before the obj.wg.Done()
		if !obj.initialized {
			err := fmt.Errorf("%s: GAPI is not initialized", Name)
			next := gapi.Next{
				Err:  err,
				Exit: true, // exit, b/c programming error?
			}
			select {
			case ch <- next:
			case <-ctx.Done():
				obj.err = ctx.Err()
				return
			}
			obj.err = err
			return
		}
		startChan := make(chan struct{}) // start signal
		close(startChan)                 // kick it off!

		var pChan <-chan time.Time
		if obj.data.NoStreamWatch {
			pChan = nil
		} else {
			pChan = puppetChan()
		}

		for {
			select {
			case <-startChan: // kick the loop once at start
				startChan = nil // disable
				// pass
			case _, ok := <-pChan:
				if !ok { // the channel closed!
					return
				}
			case <-ctx.Done():
				obj.err = ctx.Err()
				return
			}

			if obj.data.NoStreamWatch {
				pChan = nil
			} else {
				pChan = puppetChan() // TODO: okay to update interval in case it changed?
			}

			obj.data.Logf("generating new graph...")
			g, err := obj.graph()
			if err != nil {
				obj.err = err
				return
			}

			next := gapi.Next{
				Graph: g,
				//Exit: true, // TODO: for permanent shutdown!
				Err: nil,
			}
			select {
			case ch <- next: // trigger a run (send a msg)
			// unblock if we exit while waiting to send!
			case <-ctx.Done():
				obj.err = ctx.Err()
				return
			}
		}
	}()
	return ch
}

// Err will contain the last error when Next shuts down. It waits for all the
// running processes to exit before it returns.
func (obj *GAPI) Err() error {
	obj.wg.Wait()
	return obj.err
}

// cleanup cleans up the Puppet GAPI.
func (obj *GAPI) cleanup() error {
	if !obj.initialized {
		return fmt.Errorf("%s: GAPI is not initialized", Name)
	}

	if obj.puppetFile != "" {
		os.Remove(obj.puppetFile) // clean up, don't bother with error
	}
	// make this as safe as possible, check we're removing a tempdir too!
	if obj.puppetDir != "" && obj.puppetDir != "/" && strings.HasPrefix(obj.puppetDir, os.TempDir()) {
		os.RemoveAll(obj.puppetDir)
	}
	obj.puppetString = "" // free!
	if obj.puppetConf != "" {
		os.Remove(obj.puppetConf)
	}

	obj.wg.Wait()
	obj.initialized = false // closed = true
	return nil
}