package lfsapi

import (
	"bytes"
	"fmt"
	"os/exec"
	"strings"
)

type CredentialHelper interface {
	Fill(Creds) (Creds, error)
	Reject(Creds) error
	Approve(Creds) error
}

type Creds map[string]string

func (c Creds) Buffer() *bytes.Buffer {
	buf := new(bytes.Buffer)

	for k, v := range c {
		buf.Write([]byte(k))
		buf.Write([]byte("="))
		buf.Write([]byte(v))
		buf.Write([]byte("\n"))
	}

	return buf
}

type CommandCredentialHelper struct {
	SkipPrompt bool
}

func (h *CommandCredentialHelper) Fill(creds Creds) (Creds, error) {
	return h.exec("fill", creds)
}

func (h *CommandCredentialHelper) Reject(creds Creds) error {
	_, err := h.exec("reject", creds)
	return err
}

func (h *CommandCredentialHelper) Approve(creds Creds) error {
	_, err := h.exec("approve", creds)
	return err
}

func (h *CommandCredentialHelper) exec(subcommand string, input Creds) (Creds, error) {
	output := new(bytes.Buffer)
	cmd := exec.Command("git", "credential", subcommand)
	cmd.Stdin = input.Buffer()
	cmd.Stdout = output
	/*
	   There is a reason we don't hook up stderr here:
	   Git's credential cache daemon helper does not close its stderr, so if this
	   process is the process that fires up the daemon, it will wait forever
	   (until the daemon exits, really) trying to read from stderr.

	   See https://github.com/git-lfs/git-lfs/issues/117 for more details.
	*/

	err := cmd.Start()
	if err == nil {
		err = cmd.Wait()
	}

	if _, ok := err.(*exec.ExitError); ok {
		if h.SkipPrompt {
			return nil, fmt.Errorf("Change the GIT_TERMINAL_PROMPT env var to be prompted to enter your credentials for %s://%s.",
				input["protocol"], input["host"])
		}

		// 'git credential' exits with 128 if the helper doesn't fill the username
		// and password values.
		if subcommand == "fill" && err.Error() == "exit status 128" {
			return nil, nil
		}
	}

	if err != nil {
		return nil, fmt.Errorf("'git credential %s' error: %s\n", subcommand, err.Error())
	}

	creds := make(Creds)
	for _, line := range strings.Split(output.String(), "\n") {
		pieces := strings.SplitN(line, "=", 2)
		if len(pieces) < 2 || len(pieces[1]) < 1 {
			continue
		}
		creds[pieces[0]] = pieces[1]
	}

	return creds, nil
}