// 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 (
	"context"
	"sync"
	"time"

	"github.com/zclconf/go-cty/cty"

	"github.com/opentofu/opentofu/internal/addrs"
	"github.com/opentofu/opentofu/internal/checks"
	"github.com/opentofu/opentofu/internal/configs"
	"github.com/opentofu/opentofu/internal/encryption"
	"github.com/opentofu/opentofu/internal/instances"
	"github.com/opentofu/opentofu/internal/plans"
	"github.com/opentofu/opentofu/internal/refactoring"
	"github.com/opentofu/opentofu/internal/states"
	"github.com/opentofu/opentofu/internal/tfdiags"
)

// ContextGraphWalker is the GraphWalker implementation used with the
// Context struct to walk and evaluate the graph.
type ContextGraphWalker struct {
	NullGraphWalker

	// Configurable values
	Context                 *Context
	State                   *states.SyncState       // Used for safe concurrent access to state
	RefreshState            *states.SyncState       // Used for safe concurrent access to state
	PrevRunState            *states.SyncState       // Used for safe concurrent access to state
	Changes                 *plans.ChangesSync      // Used for safe concurrent writes to changes
	Checks                  *checks.State           // Used for safe concurrent writes of checkable objects and their check results
	InstanceExpander        *instances.Expander     // Tracks our gradual expansion of module and resource instances
	ImportResolver          *ImportResolver         // Tracks import targets as they are being resolved
	MoveResults             refactoring.MoveResults // Read-only record of earlier processing of move statements
	Operation               walkOperation
	StopContext             context.Context
	RootVariableValues      InputValues
	Config                  *configs.Config
	PlanTimestamp           time.Time
	Encryption              encryption.Encryption
	ProviderFunctionTracker ProviderFunctionMapping

	// This is an output. Do not set this, nor read it while a graph walk
	// is in progress.
	NonFatalDiagnostics tfdiags.Diagnostics

	once        sync.Once
	contextLock sync.Mutex
	contexts    map[string]*BuiltinEvalContext

	variableValuesLock sync.Mutex
	variableValues     map[string]map[string]cty.Value

	providerInputConfigLock sync.Mutex
}

var _ GraphWalker = (*ContextGraphWalker)(nil)

func (w *ContextGraphWalker) EnterPath(path addrs.ModuleInstance) EvalContext {
	w.contextLock.Lock()
	defer w.contextLock.Unlock()

	// If we already have a context for this path cached, use that
	key := path.String()
	if ctx, ok := w.contexts[key]; ok {
		return ctx
	}

	ctx := w.EvalContext().WithPath(path)
	w.contexts[key] = ctx.(*BuiltinEvalContext)
	return ctx
}

func (w *ContextGraphWalker) EvalContext() EvalContext {
	w.once.Do(w.init)

	// Our evaluator shares some locks with the main context and the walker
	// so that we can safely run multiple evaluations at once across
	// different modules.
	evaluator := &Evaluator{
		Meta:               w.Context.meta,
		Config:             w.Config,
		Operation:          w.Operation,
		State:              w.State,
		Changes:            w.Changes,
		Plugins:            w.Context.plugins,
		VariableValues:     w.variableValues,
		VariableValuesLock: &w.variableValuesLock,
		PlanTimestamp:      w.PlanTimestamp,
	}

	ctx := &BuiltinEvalContext{
		StopContext:             w.StopContext,
		Hooks:                   w.Context.hooks,
		InputValue:              w.Context.uiInput,
		InstanceExpanderValue:   w.InstanceExpander,
		Plugins:                 w.Context.plugins,
		MoveResultsValue:        w.MoveResults,
		ImportResolverValue:     w.ImportResolver,
		ProviderInputConfigLock: &w.providerInputConfigLock,
		ProviderInputConfig:     w.Context.providerInputConfig,
		ChangesValue:            w.Changes,
		ChecksValue:             w.Checks,
		StateValue:              w.State,
		RefreshStateValue:       w.RefreshState,
		PrevRunStateValue:       w.PrevRunState,
		Evaluator:               evaluator,
		VariableValues:          w.variableValues,
		VariableValuesLock:      &w.variableValuesLock,
		Encryption:              w.Encryption,
		ProviderFunctionTracker: w.ProviderFunctionTracker,
	}

	return ctx
}

func (w *ContextGraphWalker) init() {
	w.contexts = make(map[string]*BuiltinEvalContext)
	w.variableValues = make(map[string]map[string]cty.Value)

	// Populate root module variable values. Other modules will be populated
	// during the graph walk.
	w.variableValues[""] = make(map[string]cty.Value)
	for k, iv := range w.RootVariableValues {
		w.variableValues[""][k] = iv.Value
	}
}

func (w *ContextGraphWalker) Execute(ctx context.Context, evalCtx EvalContext, n GraphNodeExecutable) tfdiags.Diagnostics {
	// Acquire a lock on the semaphore
	w.Context.parallelSem.Acquire()
	defer w.Context.parallelSem.Release()

	return n.Execute(ctx, evalCtx, w.Operation)
}
