package configs

import (
	version "github.com/hashicorp/go-version"
	"github.com/hashicorp/hcl/v2"
	"github.com/hashicorp/terraform/addrs"
)

// RequiredProvider represents a declaration of a dependency on a particular
// provider version or source without actually configuring that provider. This
// is used in child modules that expect a provider to be passed in from their
// parent.
type RequiredProvider struct {
	Name        string
	Type        addrs.Provider
	Requirement VersionConstraint
	DeclRange   hcl.Range
}

type RequiredProviders struct {
	RequiredProviders map[string]*RequiredProvider
	DeclRange         hcl.Range
}

func decodeRequiredProvidersBlock(block *hcl.Block) (*RequiredProviders, hcl.Diagnostics) {
	attrs, diags := block.Body.JustAttributes()
	ret := &RequiredProviders{
		RequiredProviders: make(map[string]*RequiredProvider),
		DeclRange:         block.DefRange,
	}
	for name, attr := range attrs {
		expr, err := attr.Expr.Value(nil)
		if err != nil {
			diags = append(diags, err...)
		}

		rp := &RequiredProvider{
			Name:      name,
			DeclRange: attr.Expr.Range(),
		}

		switch {
		case expr.Type().IsPrimitiveType():
			vc, reqDiags := decodeVersionConstraint(attr)
			diags = append(diags, reqDiags...)
			rp.Requirement = vc

		case expr.Type().IsObjectType():
			if expr.Type().HasAttribute("version") {
				vc := VersionConstraint{
					DeclRange: attr.Range,
				}
				constraintStr := expr.GetAttr("version").AsString()
				constraints, err := version.NewConstraint(constraintStr)
				if err != nil {
					// NewConstraint doesn't return user-friendly errors, so we'll just
					// ignore the provided error and produce our own generic one.
					diags = append(diags, &hcl.Diagnostic{
						Severity: hcl.DiagError,
						Summary:  "Invalid version constraint",
						Detail:   "This string does not use correct version constraint syntax.",
						Subject:  attr.Expr.Range().Ptr(),
					})
				} else {
					vc.Required = constraints
					rp.Requirement = vc
				}
			}
			if expr.Type().HasAttribute("source") {
				fqn, sourceDiags := addrs.ParseProviderSourceString(expr.GetAttr("source").AsString())

				if sourceDiags.HasErrors() {
					hclDiags := sourceDiags.ToHCL()
					// The diagnostics from ParseProviderSourceString don't contain
					// source location information because it has no context to compute
					// them from, and so we'll add those in quickly here before we
					// return.
					for _, diag := range hclDiags {
						if diag.Subject == nil {
							diag.Subject = attr.Expr.Range().Ptr()
						}
					}
					diags = append(diags, hclDiags...)
				} else {
					rp.Type = fqn
				}
			}

		default:
			// should not happen
			diags = append(diags, &hcl.Diagnostic{
				Severity: hcl.DiagError,
				Summary:  "Invalid required_providers syntax",
				Detail:   "required_providers entries must be strings or objects.",
				Subject:  attr.Expr.Range().Ptr(),
			})
		}

		if rp.Type.IsZero() {
			pType, err := addrs.ParseProviderPart(rp.Name)
			if err != nil {
				diags = append(diags, &hcl.Diagnostic{
					Severity: hcl.DiagError,
					Summary:  "Invalid provider name",
					Detail:   err.Error(),
					Subject:  attr.Expr.Range().Ptr(),
				})
			} else {
				rp.Type = addrs.ImpliedProviderForUnqualifiedType(pType)
			}
		}

		ret.RequiredProviders[rp.Name] = rp
	}

	return ret, diags
}