package statefile

import (
	"encoding/json"
	"fmt"

	"github.com/hashicorp/terraform/internal/tfdiags"
)

func readStateV1(src []byte) (*File, tfdiags.Diagnostics) {
	var diags tfdiags.Diagnostics
	sV1 := &stateV1{}
	err := json.Unmarshal(src, sV1)
	if err != nil {
		diags = diags.Append(jsonUnmarshalDiags(err))
		return nil, diags
	}

	file, prepDiags := prepareStateV1(sV1)
	diags = diags.Append(prepDiags)
	return file, diags
}

func prepareStateV1(sV1 *stateV1) (*File, tfdiags.Diagnostics) {
	var diags tfdiags.Diagnostics
	sV2, err := upgradeStateV1ToV2(sV1)
	if err != nil {
		diags = diags.Append(tfdiags.Sourceless(
			tfdiags.Error,
			upgradeFailed,
			fmt.Sprintf("Error upgrading state file format from version 1 to version 2: %s.", err),
		))
		return nil, diags
	}

	file, prepDiags := prepareStateV2(sV2)
	diags = diags.Append(prepDiags)
	return file, diags
}

// stateV1 is a representation of the legacy JSON state format version 1.
//
// It is only used to read version 1 JSON files prior to upgrading them to
// the current format.
type stateV1 struct {
	// Version is the protocol version. "1" for a StateV1.
	Version int `json:"version"`

	// Serial is incremented on any operation that modifies
	// the State file. It is used to detect potentially conflicting
	// updates.
	Serial int64 `json:"serial"`

	// Remote is used to track the metadata required to
	// pull and push state files from a remote storage endpoint.
	Remote *remoteStateV1 `json:"remote,omitempty"`

	// Modules contains all the modules in a breadth-first order
	Modules []*moduleStateV1 `json:"modules"`
}

type remoteStateV1 struct {
	// Type controls the client we use for the remote state
	Type string `json:"type"`

	// Config is used to store arbitrary configuration that
	// is type specific
	Config map[string]string `json:"config"`
}

type moduleStateV1 struct {
	// Path is the import path from the root module. Modules imports are
	// always disjoint, so the path represents amodule tree
	Path []string `json:"path"`

	// Outputs declared by the module and maintained for each module
	// even though only the root module technically needs to be kept.
	// This allows operators to inspect values at the boundaries.
	Outputs map[string]string `json:"outputs"`

	// Resources is a mapping of the logically named resource to
	// the state of the resource. Each resource may actually have
	// N instances underneath, although a user only needs to think
	// about the 1:1 case.
	Resources map[string]*resourceStateV1 `json:"resources"`

	// Dependencies are a list of things that this module relies on
	// existing to remain intact. For example: an module may depend
	// on a VPC ID given by an aws_vpc resource.
	//
	// Terraform uses this information to build valid destruction
	// orders and to warn the user if they're destroying a module that
	// another resource depends on.
	//
	// Things can be put into this list that may not be managed by
	// Terraform. If Terraform doesn't find a matching ID in the
	// overall state, then it assumes it isn't managed and doesn't
	// worry about it.
	Dependencies []string `json:"depends_on,omitempty"`
}

type resourceStateV1 struct {
	// This is filled in and managed by Terraform, and is the resource
	// type itself such as "mycloud_instance". If a resource provider sets
	// this value, it won't be persisted.
	Type string `json:"type"`

	// Dependencies are a list of things that this resource relies on
	// existing to remain intact. For example: an AWS instance might
	// depend on a subnet (which itself might depend on a VPC, and so
	// on).
	//
	// Terraform uses this information to build valid destruction
	// orders and to warn the user if they're destroying a resource that
	// another resource depends on.
	//
	// Things can be put into this list that may not be managed by
	// Terraform. If Terraform doesn't find a matching ID in the
	// overall state, then it assumes it isn't managed and doesn't
	// worry about it.
	Dependencies []string `json:"depends_on,omitempty"`

	// Primary is the current active instance for this resource.
	// It can be replaced but only after a successful creation.
	// This is the instances on which providers will act.
	Primary *instanceStateV1 `json:"primary"`

	// Tainted is used to track any underlying instances that
	// have been created but are in a bad or unknown state and
	// need to be cleaned up subsequently.  In the
	// standard case, there is only at most a single instance.
	// However, in pathological cases, it is possible for the number
	// of instances to accumulate.
	Tainted []*instanceStateV1 `json:"tainted,omitempty"`

	// Deposed is used in the mechanics of CreateBeforeDestroy: the existing
	// Primary is Deposed to get it out of the way for the replacement Primary to
	// be created by Apply. If the replacement Primary creates successfully, the
	// Deposed instance is cleaned up. If there were problems creating the
	// replacement, the instance remains in the Deposed list so it can be
	// destroyed in a future run. Functionally, Deposed instances are very
	// similar to Tainted instances in that Terraform is only tracking them in
	// order to remember to destroy them.
	Deposed []*instanceStateV1 `json:"deposed,omitempty"`

	// Provider is used when a resource is connected to a provider with an alias.
	// If this string is empty, the resource is connected to the default provider,
	// e.g. "aws_instance" goes with the "aws" provider.
	// If the resource block contained a "provider" key, that value will be set here.
	Provider string `json:"provider,omitempty"`
}

type instanceStateV1 struct {
	// A unique ID for this resource. This is opaque to Terraform
	// and is only meant as a lookup mechanism for the providers.
	ID string `json:"id"`

	// Attributes are basic information about the resource. Any keys here
	// are accessible in variable format within Terraform configurations:
	// ${resourcetype.name.attribute}.
	Attributes map[string]string `json:"attributes,omitempty"`

	// Meta is a simple K/V map that is persisted to the State but otherwise
	// ignored by Terraform core. It's meant to be used for accounting by
	// external client code.
	Meta map[string]string `json:"meta,omitempty"`
}