package terraform

import (
	"fmt"
	"log"

	"github.com/hashicorp/hcl/v2"
	"github.com/hashicorp/terraform/addrs"
	"github.com/hashicorp/terraform/configs"
	"github.com/hashicorp/terraform/dag"
	"github.com/hashicorp/terraform/instances"
	"github.com/hashicorp/terraform/lang"
	"github.com/hashicorp/terraform/tfdiags"
	"github.com/zclconf/go-cty/cty"
	"github.com/zclconf/go-cty/cty/convert"
)

// nodeExpandModuleVariable is the placeholder for an variable that has not yet had
// its module path expanded.
type nodeExpandModuleVariable struct {
	Addr   addrs.InputVariable
	Module addrs.Module
	Config *configs.Variable
	Expr   hcl.Expression
}

var (
	_ GraphNodeDynamicExpandable = (*nodeExpandModuleVariable)(nil)
	_ GraphNodeReferenceOutside  = (*nodeExpandModuleVariable)(nil)
	_ GraphNodeReferenceable     = (*nodeExpandModuleVariable)(nil)
	_ GraphNodeReferencer        = (*nodeExpandModuleVariable)(nil)
	_ graphNodeTemporaryValue    = (*nodeExpandModuleVariable)(nil)
	_ graphNodeExpandsInstances  = (*nodeExpandModuleVariable)(nil)
)

func (n *nodeExpandModuleVariable) expandsInstances() {}

func (n *nodeExpandModuleVariable) temporaryValue() bool {
	return true
}

func (n *nodeExpandModuleVariable) DynamicExpand(ctx EvalContext) (*Graph, error) {
	var g Graph
	expander := ctx.InstanceExpander()
	for _, module := range expander.ExpandModule(n.Module) {
		o := &nodeModuleVariable{
			Addr:           n.Addr.Absolute(module),
			Config:         n.Config,
			Expr:           n.Expr,
			ModuleInstance: module,
		}
		g.Add(o)
	}
	return &g, nil
}

func (n *nodeExpandModuleVariable) Name() string {
	return fmt.Sprintf("%s.%s (expand)", n.Module, n.Addr.String())
}

// GraphNodeModulePath
func (n *nodeExpandModuleVariable) ModulePath() addrs.Module {
	return n.Module
}

// GraphNodeReferencer
func (n *nodeExpandModuleVariable) References() []*addrs.Reference {

	// If we have no value expression, we cannot depend on anything.
	if n.Expr == nil {
		return nil
	}

	// Variables in the root don't depend on anything, because their values
	// are gathered prior to the graph walk and recorded in the context.
	if len(n.Module) == 0 {
		return nil
	}

	// Otherwise, we depend on anything referenced by our value expression.
	// We ignore diagnostics here under the assumption that we'll re-eval
	// all these things later and catch them then; for our purposes here,
	// we only care about valid references.
	//
	// Due to our GraphNodeReferenceOutside implementation, the addresses
	// returned by this function are interpreted in the _parent_ module from
	// where our associated variable was declared, which is correct because
	// our value expression is assigned within a "module" block in the parent
	// module.
	refs, _ := lang.ReferencesInExpr(n.Expr)
	return refs
}

// GraphNodeReferenceOutside implementation
func (n *nodeExpandModuleVariable) ReferenceOutside() (selfPath, referencePath addrs.Module) {
	return n.Module, n.Module.Parent()
}

// GraphNodeReferenceable
func (n *nodeExpandModuleVariable) ReferenceableAddrs() []addrs.Referenceable {
	return []addrs.Referenceable{n.Addr}
}

// nodeModuleVariable represents a module variable input during
// the apply step.
type nodeModuleVariable struct {
	Addr   addrs.AbsInputVariableInstance
	Config *configs.Variable // Config is the var in the config
	Expr   hcl.Expression    // Expr is the value expression given in the call
	// ModuleInstance in order to create the appropriate context for evaluating
	// ModuleCallArguments, ex. so count.index and each.key can resolve
	ModuleInstance addrs.ModuleInstance
}

// Ensure that we are implementing all of the interfaces we think we are
// implementing.
var (
	_ GraphNodeModuleInstance = (*nodeModuleVariable)(nil)
	_ GraphNodeExecutable     = (*nodeModuleVariable)(nil)
	_ graphNodeTemporaryValue = (*nodeModuleVariable)(nil)
	_ dag.GraphNodeDotter     = (*nodeModuleVariable)(nil)
)

func (n *nodeModuleVariable) temporaryValue() bool {
	return true
}

func (n *nodeModuleVariable) Name() string {
	return n.Addr.String()
}

// GraphNodeModuleInstance
func (n *nodeModuleVariable) Path() addrs.ModuleInstance {
	// We execute in the parent scope (above our own module) because
	// expressions in our value are resolved in that context.
	return n.Addr.Module.Parent()
}

// GraphNodeModulePath
func (n *nodeModuleVariable) ModulePath() addrs.Module {
	return n.Addr.Module.Module()
}

// GraphNodeExecutable
func (n *nodeModuleVariable) Execute(ctx EvalContext, op walkOperation) (diags tfdiags.Diagnostics) {
	// If we have no value, do nothing
	if n.Expr == nil {
		return nil
	}

	// Otherwise, interpolate the value of this variable and set it
	// within the variables mapping.
	var vals map[string]cty.Value
	var err error

	switch op {
	case walkValidate:
		vals, err = n.EvalModuleCallArgument(ctx, true)
		diags = diags.Append(err)
		if diags.HasErrors() {
			return diags
		}
	default:
		vals, err = n.EvalModuleCallArgument(ctx, false)
		diags = diags.Append(err)
		if diags.HasErrors() {
			return diags
		}
	}

	// Set values for arguments of a child module call, for later retrieval
	// during expression evaluation.
	_, call := n.Addr.Module.CallInstance()
	ctx.SetModuleCallArguments(call, vals)

	return evalVariableValidations(n.Addr, n.Config, n.Expr, ctx)
}

// dag.GraphNodeDotter impl.
func (n *nodeModuleVariable) DotNode(name string, opts *dag.DotOpts) *dag.DotNode {
	return &dag.DotNode{
		Name: name,
		Attrs: map[string]string{
			"label": n.Name(),
			"shape": "note",
		},
	}
}

// EvalModuleCallArgument produces the value for a particular variable as will
// be used by a child module instance.
//
// The result is written into a map, with its key set to the local name of the
// variable, disregarding the module instance address. A map is returned instead
// of a single value as a result of trying to be convenient for use with
// EvalContext.SetModuleCallArguments, which expects a map to merge in with any
// existing arguments.
//
// validateOnly indicates that this evaluation is only for config
// validation, and we will not have any expansion module instance
// repetition data.
func (n *nodeModuleVariable) EvalModuleCallArgument(ctx EvalContext, validateOnly bool) (map[string]cty.Value, error) {
	wantType := n.Config.Type
	name := n.Addr.Variable.Name
	expr := n.Expr

	if expr == nil {
		// Should never happen, but we'll bail out early here rather than
		// crash in case it does. We set no value at all in this case,
		// making a subsequent call to EvalContext.SetModuleCallArguments
		// a no-op.
		log.Printf("[ERROR] attempt to evaluate %s with nil expression", n.Addr.String())
		return nil, nil
	}

	var moduleInstanceRepetitionData instances.RepetitionData

	switch {
	case validateOnly:
		// the instance expander does not track unknown expansion values, so we
		// have to assume all RepetitionData is unknown.
		moduleInstanceRepetitionData = instances.RepetitionData{
			CountIndex: cty.UnknownVal(cty.Number),
			EachKey:    cty.UnknownVal(cty.String),
			EachValue:  cty.DynamicVal,
		}

	default:
		// Get the repetition data for this module instance,
		// so we can create the appropriate scope for evaluating our expression
		moduleInstanceRepetitionData = ctx.InstanceExpander().GetModuleInstanceRepetitionData(n.ModuleInstance)
	}

	scope := ctx.EvaluationScope(nil, moduleInstanceRepetitionData)
	val, diags := scope.EvalExpr(expr, cty.DynamicPseudoType)

	// We intentionally passed DynamicPseudoType to EvalExpr above because
	// now we can do our own local type conversion and produce an error message
	// with better context if it fails.
	var convErr error
	val, convErr = convert.Convert(val, wantType)
	if convErr != nil {
		diags = diags.Append(&hcl.Diagnostic{
			Severity: hcl.DiagError,
			Summary:  "Invalid value for module argument",
			Detail: fmt.Sprintf(
				"The given value is not suitable for child module variable %q defined at %s: %s.",
				name, n.Config.DeclRange.String(), convErr,
			),
			Subject: expr.Range().Ptr(),
		})
		// We'll return a placeholder unknown value to avoid producing
		// redundant downstream errors.
		val = cty.UnknownVal(wantType)
	}

	vals := make(map[string]cty.Value)
	vals[name] = val
	return vals, diags.ErrWithWarnings()
}