package terraform

import (
	"log"

	"github.com/hashicorp/terraform/internal/addrs"
	"github.com/hashicorp/terraform/internal/configs"
	"github.com/hashicorp/terraform/internal/states"
	"github.com/hashicorp/terraform/internal/tfdiags"
	"github.com/zclconf/go-cty/cty"
)

// Validate performs semantic validation of a configuration, and returns
// any warnings or errors.
//
// Syntax and structural checks are performed by the configuration loader,
// and so are not repeated here.
//
// Validate considers only the configuration and so it won't catch any
// errors caused by current values in the state, or other external information
// such as root module input variables. However, the Plan function includes
// all of the same checks as Validate, in addition to the other work it does
// to consider the previous run state and the planning options.
func (c *Context) Validate(config *configs.Config) tfdiags.Diagnostics {
	defer c.acquireRun("validate")()

	var diags tfdiags.Diagnostics

	moreDiags := c.checkConfigDependencies(config)
	diags = diags.Append(moreDiags)
	// If required dependencies are not available then we'll bail early since
	// otherwise we're likely to just see a bunch of other errors related to
	// incompatibilities, which could be overwhelming for the user.
	if diags.HasErrors() {
		return diags
	}

	log.Printf("[DEBUG] Building and walking validate graph")

	// Validate is to check if the given module is valid regardless of
	// input values, current state, etc. Therefore we populate all of the
	// input values with unknown values of the expected type, allowing us
	// to perform a type check without assuming any particular values.
	varValues := make(InputValues)
	for name, variable := range config.Module.Variables {
		ty := variable.Type
		if ty == cty.NilType {
			// Can't predict the type at all, so we'll just mark it as
			// cty.DynamicVal (unknown value of cty.DynamicPseudoType).
			ty = cty.DynamicPseudoType
		}
		varValues[name] = &InputValue{
			Value:      cty.UnknownVal(ty),
			SourceType: ValueFromUnknown,
		}
	}

	graph, moreDiags := (&PlanGraphBuilder{
		Config:             config,
		Plugins:            c.plugins,
		State:              states.NewState(),
		RootVariableValues: varValues,
		Operation:          walkValidate,
	}).Build(addrs.RootModuleInstance)
	diags = diags.Append(moreDiags)
	if moreDiags.HasErrors() {
		return diags
	}

	walker, walkDiags := c.walk(graph, walkValidate, &graphWalkOpts{
		Config: config,
	})
	diags = diags.Append(walker.NonFatalDiagnostics)
	diags = diags.Append(walkDiags)
	if walkDiags.HasErrors() {
		return diags
	}

	return diags
}