package statefile

import (
	"encoding/json"
	"fmt"

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

func readStateV2(src []byte) (*File, tfdiags.Diagnostics) {
	var diags tfdiags.Diagnostics
	sV2 := &stateV2{}
	err := json.Unmarshal(src, sV2)
	if err != nil {
		diags = diags.Append(jsonUnmarshalDiags(err))
		return nil, diags
	}

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

func prepareStateV2(sV2 *stateV2) (*File, tfdiags.Diagnostics) {
	var diags tfdiags.Diagnostics
	sV3, err := upgradeStateV2ToV3(sV2)
	if err != nil {
		diags = diags.Append(tfdiags.Sourceless(
			tfdiags.Error,
			upgradeFailed,
			fmt.Sprintf("Error upgrading state file format from version 2 to version 3: %s.", err),
		))
		return nil, diags
	}

	file, prepDiags := prepareStateV3(sV3)
	diags = diags.Append(prepDiags)
	return file, diags
}

// stateV2 is a representation of the legacy JSON state format version 2.
//
// It is only used to read version 2 JSON files prior to upgrading them to
// the current format.
type stateV2 struct {
	// Version is the state file protocol version.
	Version int `json:"version"`

	// TFVersion is the version of Terraform that wrote this state.
	TFVersion string `json:"terraform_version,omitempty"`

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

	// Lineage is set when a new, blank state is created and then
	// never updated. This allows us to determine whether the serials
	// of two states can be meaningfully compared.
	// Apart from the guarantee that collisions between two lineages
	// are very unlikely, this value is opaque and external callers
	// should only compare lineage strings byte-for-byte for equality.
	Lineage string `json:"lineage"`

	// Remote is used to track the metadata required to
	// pull and push state files from a remote storage endpoint.
	Remote *remoteStateV2 `json:"remote,omitempty"`

	// Backend tracks the configuration for the backend in use with
	// this state. This is used to track any changes in the backend
	// configuration.
	Backend *backendStateV2 `json:"backend,omitempty"`

	// Modules contains all the modules in a breadth-first order
	Modules []*moduleStateV2 `json:"modules"`
}

type remoteStateV2 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 outputStateV2 struct {
	// Sensitive describes whether the output is considered sensitive,
	// which may lead to masking the value on screen in some cases.
	Sensitive bool `json:"sensitive"`
	// Type describes the structure of Value. Valid values are "string",
	// "map" and "list"
	Type string `json:"type"`
	// Value contains the value of the output, in the structure described
	// by the Type field.
	Value interface{} `json:"value"`
}

type moduleStateV2 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"`

	// Locals are kept only transiently in-memory, because we can always
	// re-compute them.
	Locals map[string]interface{} `json:"-"`

	// 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]*outputStateV2 `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]*resourceStateV2 `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"`
}

type resourceStateV2 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"`

	// 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 *instanceStateV2 `json:"primary"`

	// 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 Primary, the Deposed
	// instance and the (now tainted) replacement Primary will be swapped so the
	// tainted replacement will be cleaned up instead.
	//
	// An instance will remain in the Deposed list until it is successfully
	// destroyed and purged.
	Deposed []*instanceStateV2 `json:"deposed"`

	// 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"`
}

type instanceStateV2 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"`

	// 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. The value here must only contain Go primitives
	// and collections.
	Meta map[string]interface{} `json:"meta"`

	// Tainted is used to mark a resource for recreation.
	Tainted bool `json:"tainted"`
}

type backendStateV2 struct {
	Type      string          `json:"type"`   // Backend type
	ConfigRaw json.RawMessage `json:"config"` // Backend raw config
	Hash      uint64          `json:"hash"`   // Hash of portion of configuration from config files
}