// Copyright (c) The OpenTofu Authors
// SPDX-License-Identifier: MPL-2.0
// Copyright (c) 2023 HashiCorp, Inc.
// SPDX-License-Identifier: MPL-2.0

package tofu

import (
	"github.com/opentofu/opentofu/internal/addrs"
	"github.com/opentofu/opentofu/internal/configs"
	"github.com/opentofu/opentofu/internal/dag"
	"github.com/opentofu/opentofu/internal/states"
	"github.com/opentofu/opentofu/internal/tfdiags"
)

// EvalGraphBuilder implements GraphBuilder and constructs a graph suitable
// for evaluating in-memory values (input variables, local values, output
// values) in the state without any other side-effects.
//
// This graph is used only in weird cases, such as the "tofu console"
// CLI command, where we need to evaluate expressions against the state
// without taking any other actions.
//
// The generated graph will include nodes for providers, resources, etc
// just to allow indirect dependencies to be resolved, but these nodes will
// not take any actions themselves since we assume that their parts of the
// state, if any, are already complete.
//
// Although the providers are never configured, they must still be available
// in order to obtain schema information used for type checking, etc.
type EvalGraphBuilder struct {
	// Config is the configuration tree.
	Config *configs.Config

	// State is the current state
	State *states.State

	// RootVariableValues are the raw input values for root input variables
	// given by the caller, which we'll resolve into final values as part
	// of the plan walk.
	RootVariableValues InputValues

	// Plugins is a library of plug-in components (providers and
	// provisioners) available for use.
	Plugins *contextPlugins
}

// See GraphBuilder
func (b *EvalGraphBuilder) Build(path addrs.ModuleInstance) (*Graph, tfdiags.Diagnostics) {
	return (&BasicGraphBuilder{
		Steps: b.Steps(),
		Name:  "EvalGraphBuilder",
	}).Build(path)
}

// See GraphBuilder
func (b *EvalGraphBuilder) Steps() []GraphTransformer {
	concreteProvider := func(a *NodeAbstractProvider) dag.Vertex {
		return &NodeEvalableProvider{
			NodeAbstractProvider: a,
		}
	}

	steps := []GraphTransformer{
		// Creates all the data resources that aren't in the state. This will also
		// add any orphans from scaling in as destroy nodes.
		&ConfigTransformer{
			Config: b.Config,
		},

		// Add dynamic values
		&RootVariableTransformer{Config: b.Config, RawValues: b.RootVariableValues},
		&ModuleVariableTransformer{Config: b.Config},
		&LocalTransformer{Config: b.Config},
		&OutputTransformer{
			Config:   b.Config,
			Planning: true,
		},

		// Attach the configuration to any resources
		&AttachResourceConfigTransformer{Config: b.Config},

		// Attach the state
		&AttachStateTransformer{State: b.State},

		transformProviders(concreteProvider, b.Config),

		// Must attach schemas before ReferenceTransformer so that we can
		// analyze the configuration to find references.
		&AttachSchemaTransformer{Plugins: b.Plugins, Config: b.Config},

		// After schema transformer, we can add function references
		&ProviderFunctionTransformer{Config: b.Config},

		// Remove unused providers and proxies
		&PruneProviderTransformer{},

		// Create expansion nodes for all of the module calls. This must
		// come after all other transformers that create nodes representing
		// objects that can belong to modules.
		&ModuleExpansionTransformer{Config: b.Config},

		// Connect so that the references are ready for targeting. We'll
		// have to connect again later for providers and so on.
		&ReferenceTransformer{},

		// Although we don't configure providers, we do still start them up
		// to get their schemas, and so we must shut them down again here.
		&CloseProviderTransformer{},

		// Close root module
		&CloseRootModuleTransformer{
			RootConfig: b.Config,
		},

		// Remove redundant edges to simplify the graph.
		&TransitiveReductionTransformer{},
	}

	return steps
}
