package command

import (
	"fmt"
	"log"
	"os"
	"sort"
	"strings"

	multierror "github.com/hashicorp/go-multierror"
	"github.com/hashicorp/terraform/backend"
	"github.com/hashicorp/terraform/config"
	"github.com/hashicorp/terraform/config/module"
	"github.com/hashicorp/terraform/helper/variables"
	"github.com/hashicorp/terraform/plugin"
	"github.com/hashicorp/terraform/plugin/discovery"
	"github.com/hashicorp/terraform/terraform"
)

// InitCommand is a Command implementation that takes a Terraform
// module and clones it to the working directory.
type InitCommand struct {
	Meta

	// getPlugins is for the -get-plugins flag
	getPlugins bool

	// providerInstaller is used to download and install providers that
	// aren't found locally. This uses a discovery.ProviderInstaller instance
	// by default, but it can be overridden here as a way to mock fetching
	// providers for tests.
	providerInstaller discovery.Installer
}

func (c *InitCommand) Run(args []string) int {
	var flagBackend, flagGet, flagUpgrade bool
	var flagConfigExtra map[string]interface{}
	var flagPluginPath FlagStringSlice
	var flagVerifyPlugins bool

	args = c.Meta.process(args, false)
	cmdFlags := c.flagSet("init")
	cmdFlags.BoolVar(&flagBackend, "backend", true, "")
	cmdFlags.Var((*variables.FlagAny)(&flagConfigExtra), "backend-config", "")
	cmdFlags.BoolVar(&flagGet, "get", true, "")
	cmdFlags.BoolVar(&c.getPlugins, "get-plugins", true, "")
	cmdFlags.BoolVar(&c.forceInitCopy, "force-copy", false, "suppress prompts about copying state data")
	cmdFlags.BoolVar(&c.Meta.stateLock, "lock", true, "lock state")
	cmdFlags.DurationVar(&c.Meta.stateLockTimeout, "lock-timeout", 0, "lock timeout")
	cmdFlags.BoolVar(&c.reconfigure, "reconfigure", false, "reconfigure")
	cmdFlags.BoolVar(&flagUpgrade, "upgrade", false, "")
	cmdFlags.Var(&flagPluginPath, "plugin-dir", "plugin directory")
	cmdFlags.BoolVar(&flagVerifyPlugins, "verify-plugins", true, "verify plugins")

	cmdFlags.Usage = func() { c.Ui.Error(c.Help()) }
	if err := cmdFlags.Parse(args); err != nil {
		return 1
	}

	if len(flagPluginPath) > 0 {
		c.pluginPath = flagPluginPath
		c.getPlugins = false
	}

	// set getProvider if we don't have a test version already
	if c.providerInstaller == nil {
		c.providerInstaller = &discovery.ProviderInstaller{
			Dir: c.pluginDir(),
			PluginProtocolVersion: plugin.Handshake.ProtocolVersion,
			SkipVerify:            !flagVerifyPlugins,
		}
	}

	// Validate the arg count
	args = cmdFlags.Args()
	if len(args) > 1 {
		c.Ui.Error("The init command expects at most one argument.\n")
		cmdFlags.Usage()
		return 1
	}

	if err := c.storePluginPath(c.pluginPath); err != nil {
		c.Ui.Error(fmt.Sprintf("Error saving -plugin-path values: %s", err))
		return 1
	}

	// Get our pwd. We don't always need it but always getting it is easier
	// than the logic to determine if it is or isn't needed.
	pwd, err := os.Getwd()
	if err != nil {
		c.Ui.Error(fmt.Sprintf("Error getting pwd: %s", err))
		return 1
	}

	// Get the path and source module to copy
	path := pwd
	if len(args) == 1 {
		path = args[0]
	}

	// This will track whether we outputted anything so that we know whether
	// to output a newline before the success message
	var header bool

	// If our directory is empty, then we're done. We can't get or setup
	// the backend with an empty directory.
	if empty, err := config.IsEmptyDir(path); err != nil {
		c.Ui.Error(fmt.Sprintf(
			"Error checking configuration: %s", err))
		return 1
	} else if empty {
		c.Ui.Output(c.Colorize().Color(strings.TrimSpace(outputInitEmpty)))
		return 0
	}

	var back backend.Backend

	// If we're performing a get or loading the backend, then we perform
	// some extra tasks.
	if flagGet || flagBackend {
		conf, err := c.Config(path)
		if err != nil {
			c.Ui.Error(fmt.Sprintf(
				"Error loading configuration: %s", err))
			return 1
		}

		// If we requested downloading modules and have modules in the config
		if flagGet && len(conf.Modules) > 0 {
			header = true

			getMode := module.GetModeGet
			if flagUpgrade {
				getMode = module.GetModeUpdate
				c.Ui.Output(c.Colorize().Color(fmt.Sprintf(
					"[reset][bold]Upgrading modules...")))
			} else {
				c.Ui.Output(c.Colorize().Color(fmt.Sprintf(
					"[reset][bold]Downloading modules...")))
			}

			if err := getModules(&c.Meta, path, getMode); err != nil {
				c.Ui.Error(fmt.Sprintf(
					"Error downloading modules: %s", err))
				return 1
			}

		}

		// If we're requesting backend configuration or looking for required
		// plugins, load the backend
		if flagBackend {
			header = true

			// Only output that we're initializing a backend if we have
			// something in the config. We can be UNSETTING a backend as well
			// in which case we choose not to show this.
			if conf.Terraform != nil && conf.Terraform.Backend != nil {
				c.Ui.Output(c.Colorize().Color(fmt.Sprintf(
					"\n[reset][bold]Initializing the backend...")))
			}

			opts := &BackendOpts{
				Config:      conf,
				ConfigExtra: flagConfigExtra,
				Init:        true,
			}
			if back, err = c.Backend(opts); err != nil {
				c.Ui.Error(err.Error())
				return 1
			}
		}
	}

	if back == nil {
		// If we didn't initialize a backend then we'll try to at least
		// instantiate one. This might fail if it wasn't already initalized
		// by a previous run, so we must still expect that "back" may be nil
		// in code that follows.
		back, err = c.Backend(nil)
		if err != nil {
			// This is fine. We'll proceed with no backend, then.
			back = nil
		}
	}

	var state *terraform.State

	// If we have a functional backend (either just initialized or initialized
	// on a previous run) we'll use the current state as a potential source
	// of provider dependencies.
	if back != nil {
		sMgr, err := back.State(c.Workspace())
		if err != nil {
			c.Ui.Error(fmt.Sprintf(
				"Error loading state: %s", err))
			return 1
		}

		if err := sMgr.RefreshState(); err != nil {
			c.Ui.Error(fmt.Sprintf(
				"Error refreshing state: %s", err))
			return 1
		}

		state = sMgr.State()
	}

	if v := os.Getenv(ProviderSkipVerifyEnvVar); v != "" {
		c.ignorePluginChecksum = true
	}

	// Now that we have loaded all modules, check the module tree for missing providers.
	err = c.getProviders(path, state, flagUpgrade)
	if err != nil {
		// this function provides its own output
		log.Printf("[ERROR] %s", err)
		return 1
	}

	// If we outputted information, then we need to output a newline
	// so that our success message is nicely spaced out from prior text.
	if header {
		c.Ui.Output("")
	}

	c.Ui.Output(c.Colorize().Color(strings.TrimSpace(outputInitSuccess)))

	return 0
}

// Load the complete module tree, and fetch any missing providers.
// This method outputs its own Ui.
func (c *InitCommand) getProviders(path string, state *terraform.State, upgrade bool) error {
	mod, err := c.Module(path)
	if err != nil {
		c.Ui.Error(fmt.Sprintf("Error getting plugins: %s", err))
		return err
	}

	if err := mod.Validate(); err != nil {
		c.Ui.Error(fmt.Sprintf("Error getting plugins: %s", err))
		return err
	}

	var available discovery.PluginMetaSet
	if upgrade {
		// If we're in upgrade mode, we ignore any auto-installed plugins
		// in "available", causing us to reinstall and possibly upgrade them.
		available = c.providerPluginManuallyInstalledSet()
	} else {
		available = c.providerPluginSet()
	}

	requirements := terraform.ModuleTreeDependencies(mod, state).AllPluginRequirements()
	if len(requirements) == 0 {
		// nothing to initialize
		return nil
	}

	c.Ui.Output(c.Colorize().Color(
		"\n[reset][bold]Initializing provider plugins...",
	))

	missing := c.missingPlugins(available, requirements)

	var errs error
	if c.getPlugins {
		for provider, reqd := range missing {
			c.Ui.Output(fmt.Sprintf("- Downloading plugin for provider %q...", provider))
			_, err := c.providerInstaller.Get(provider, reqd.Versions)

			if err != nil {
				switch err {
				case discovery.ErrorNoSuchProvider:
					c.Ui.Error(fmt.Sprintf(errProviderNotFound, provider, DefaultPluginVendorDir))
				case discovery.ErrorNoSuitableVersion:
					if reqd.Versions.Unconstrained() {
						// This should never happen, but might crop up if we catch
						// the releases server in a weird state where the provider's
						// directory is present but does not yet contain any
						// versions. We'll treat it like ErrorNoSuchProvider, then.
						c.Ui.Error(fmt.Sprintf(errProviderNotFound, provider, DefaultPluginVendorDir))
					} else {
						c.Ui.Error(fmt.Sprintf(errProviderVersionsUnsuitable, provider, reqd.Versions))
					}
				case discovery.ErrorNoVersionCompatible:
					// FIXME: This error message is sub-awesome because we don't
					// have enough information here to tell the user which versions
					// we considered and which versions might be compatible.
					constraint := reqd.Versions.String()
					if constraint == "" {
						constraint = "(any version)"
					}
					c.Ui.Error(fmt.Sprintf(errProviderIncompatible, provider, constraint))
				default:
					c.Ui.Error(fmt.Sprintf(errProviderInstallError, provider, err.Error(), DefaultPluginVendorDir))
				}

				errs = multierror.Append(errs, err)
			}
		}

		if errs != nil {
			return errs
		}
	} else if len(missing) > 0 {
		// we have missing providers, but aren't going to try and download them
		var lines []string
		for provider, reqd := range missing {
			if reqd.Versions.Unconstrained() {
				lines = append(lines, fmt.Sprintf("* %s (any version)\n", provider))
			} else {
				lines = append(lines, fmt.Sprintf("* %s (%s)\n", provider, reqd.Versions))
			}
			errs = multierror.Append(errs, fmt.Errorf("missing provider %q", provider))
		}
		sort.Strings(lines)
		c.Ui.Error(fmt.Sprintf(errMissingProvidersNoInstall, strings.Join(lines, ""), DefaultPluginVendorDir))
		return errs
	}

	// With all the providers downloaded, we'll generate our lock file
	// that ensures the provider binaries remain unchanged until we init
	// again. If anything changes, other commands that use providers will
	// fail with an error instructing the user to re-run this command.
	available = c.providerPluginSet() // re-discover to see newly-installed plugins
	chosen := choosePlugins(available, requirements)
	digests := map[string][]byte{}
	for name, meta := range chosen {
		digest, err := meta.SHA256()
		if err != nil {
			c.Ui.Error(fmt.Sprintf("failed to read provider plugin %s: %s", meta.Path, err))
			return err
		}
		digests[name] = digest
		if c.ignorePluginChecksum {
			digests[name] = nil
		}
	}
	err = c.providerPluginsLock().Write(digests)
	if err != nil {
		c.Ui.Error(fmt.Sprintf("failed to save provider manifest: %s", err))
		return err
	}

	{
		// Purge any auto-installed plugins that aren't being used.
		purged, err := c.providerInstaller.PurgeUnused(chosen)
		if err != nil {
			// Failure to purge old plugins is not a fatal error
			c.Ui.Warn(fmt.Sprintf("failed to purge unused plugins: %s", err))
		}
		if purged != nil {
			for meta := range purged {
				log.Printf("[DEBUG] Purged unused %s plugin %s", meta.Name, meta.Path)
			}
		}
	}

	// If any providers have "floating" versions (completely unconstrained)
	// we'll suggest the user constrain with a pessimistic constraint to
	// avoid implicitly adopting a later major release.
	constraintSuggestions := make(map[string]discovery.ConstraintStr)
	for name, meta := range chosen {
		req := requirements[name]
		if req == nil {
			// should never happen, but we don't want to crash here, so we'll
			// be cautious.
			continue
		}

		if req.Versions.Unconstrained() && meta.Version != discovery.VersionZero {
			// meta.Version.MustParse is safe here because our "chosen" metas
			// were already filtered for validity of versions.
			constraintSuggestions[name] = meta.Version.MustParse().MinorUpgradeConstraintStr()
		}
	}
	if len(constraintSuggestions) != 0 {
		names := make([]string, 0, len(constraintSuggestions))
		for name := range constraintSuggestions {
			names = append(names, name)
		}
		sort.Strings(names)

		c.Ui.Output(outputInitProvidersUnconstrained)
		for _, name := range names {
			c.Ui.Output(fmt.Sprintf("* provider.%s: version = %q", name, constraintSuggestions[name]))
		}
	}

	return nil
}

func (c *InitCommand) Help() string {
	helpText := `
Usage: terraform init [options] [DIR]

  Initialize a new or existing Terraform working directory by creating
  initial files, loading any remote state, downloading modules, etc.

  This is the first command that should be run for any new or existing
  Terraform configuration per machine. This sets up all the local data
  necessary to run Terraform that is typically not committed to version
  control.

  This command is always safe to run multiple times. Though subsequent runs
  may give errors, this command will never delete your configuration or
  state. Even so, if you have important information, please back it up prior
  to running this command, just in case.

  If no arguments are given, the configuration in this working directory
  is initialized.

Options:

  -backend=true        Configure the backend for this configuration.

  -backend-config=path This can be either a path to an HCL file with key/value
                       assignments (same format as terraform.tfvars) or a
                       'key=value' format. This is merged with what is in the
                       configuration file. This can be specified multiple
                       times. The backend type must be in the configuration
                       itself.

  -force-copy          Suppress prompts about copying state data. This is
                       equivalent to providing a "yes" to all confirmation
                       prompts.

  -get=true            Download any modules for this configuration.

  -get-plugins=true    Download any missing plugins for this configuration.

  -input=true          Ask for input if necessary. If false, will error if
                       input was required.

  -lock=true           Lock the state file when locking is supported.

  -lock-timeout=0s     Duration to retry a state lock.

  -no-color            If specified, output won't contain any color.

  -plugin-dir          Directory containing plugin binaries. This overrides all
                       default search paths for plugins, and prevents the 
                       automatic installation of plugins. This flag can be used
                       multiple times.

  -reconfigure         Reconfigure the backend, ignoring any saved
                       configuration.

  -upgrade=false       If installing modules (-get) or plugins (-get-plugins),
                       ignore previously-downloaded objects and install the
                       latest version allowed within configured constraints.

  -verify-plugins=true Verify the authenticity and integrity of automatically
                       downloaded plugins.
`
	return strings.TrimSpace(helpText)
}

func (c *InitCommand) Synopsis() string {
	return "Initialize a new or existing Terraform configuration"
}

const errInitCopyNotEmpty = `
The destination path contains Terraform configuration files. The init command
with a SOURCE parameter can only be used on a directory without existing
Terraform files.

Please resolve this issue and try again.
`

const outputInitEmpty = `
[reset][bold]Terraform initialized in an empty directory![reset]

The directory has no Terraform configuration files. You may begin working
with Terraform immediately by creating Terraform configuration files.
`

const outputInitSuccess = `
[reset][bold][green]Terraform has been successfully initialized![reset][green]

You may now begin working with Terraform. Try running "terraform plan" to see
any changes that are required for your infrastructure. All Terraform commands
should now work.

If you ever set or change modules or backend configuration for Terraform,
rerun this command to reinitialize your working directory. If you forget, other
commands will detect it and remind you to do so if necessary.
`

const outputInitProvidersUnconstrained = `
The following providers do not have any version constraints in configuration,
so the latest version was installed.

To prevent automatic upgrades to new major versions that may contain breaking
changes, it is recommended to add version = "..." constraints to the
corresponding provider blocks in configuration, with the constraint strings
suggested below.
`

const errProviderNotFound = `
[reset][bold][red]Provider %[1]q not available for installation.[reset][red]

A provider named %[1]q could not be found in the official repository.

This may result from mistyping the provider name, or the given provider may
be a third-party provider that cannot be installed automatically.

In the latter case, the plugin must be installed manually by locating and
downloading a suitable distribution package and placing the plugin's executable
file in the following directory:
    %[2]s

Terraform detects necessary plugins by inspecting the configuration and state.
To view the provider versions requested by each module, run
"terraform providers".
`

const errProviderVersionsUnsuitable = `
[reset][bold][red]No provider %[1]q plugins meet the constraint %[2]q.[reset][red]

The version constraint is derived from the "version" argument within the
provider %[1]q block in configuration. Child modules may also apply
provider version constraints. To view the provider versions requested by each
module in the current configuration, run "terraform providers".

To proceed, the version constraints for this provider must be relaxed by
either adjusting or removing the "version" argument in the provider blocks
throughout the configuration.
`

const errProviderIncompatible = `
[reset][bold][red]No available provider %[1]q plugins are compatible with this Terraform version.[reset][red]

From time to time, new Terraform major releases can change the requirements for
plugins such that older plugins become incompatible.

Terraform checked all of the plugin versions matching the given constraint:
    %[2]s

Unfortunately, none of the suitable versions are compatible with this version
of Terraform. If you have recently upgraded Terraform, it may be necessary to
move to a newer major release of this provider. Alternatively, if you are
attempting to upgrade the provider to a new major version you may need to
also upgrade Terraform to support the new version.

Consult the documentation for this provider for more information on
compatibility between provider versions and Terraform versions.
`

const errProviderInstallError = `
[reset][bold][red]Error installing provider %[1]q: %[2]s.[reset][red]

Terraform analyses the configuration and state and automatically downloads
plugins for the providers used. However, when attempting to download this
plugin an unexpected error occured.

This may be caused if for some reason Terraform is unable to reach the
plugin repository. The repository may be unreachable if access is blocked
by a firewall.

If automatic installation is not possible or desirable in your environment,
you may alternatively manually install plugins by downloading a suitable
distribution package and placing the plugin's executable file in the
following directory:
    %[3]s
`

const errMissingProvidersNoInstall = `
[reset][bold][red]Missing required providers.[reset][red]

The following provider constraints are not met by the currently-installed
provider plugins:

%[1]s
Terraform can automatically download and install plugins to meet the given
constraints, but this step was skipped due to the use of -get-plugins=false
and/or -plugin-dir on the command line.

If automatic installation is not possible or desirable in your environment,
you may manually install plugins by downloading a suitable distribution package
and placing the plugin's executable file in one of the directories given in
by -plugin-dir on the command line, or in the following directory if custom
plugin directories are not set:
    %[2]s
`