package hcl2template

import (
	"fmt"
	"strings"

	"github.com/hashicorp/hcl/v2"
	"github.com/hashicorp/hcl/v2/ext/typeexpr"
	"github.com/hashicorp/hcl/v2/gohcl"
	"github.com/hashicorp/hcl/v2/hclsyntax"
	"github.com/zclconf/go-cty/cty"
	"github.com/zclconf/go-cty/cty/convert"
)

type Variable struct {
	// CmdValue, VarfileValue, EnvValue, DefaultValue are possible values of
	// the variable; The first value set from these will be the one used. If
	// none is set; an error will be returned if a user tries to use the
	// Variable.
	CmdValue     cty.Value
	VarfileValue cty.Value
	EnvValue     cty.Value
	DefaultValue cty.Value

	// Cty Type of the variable. If the default value or a collected value is
	// not of this type nor can be converted to this type an error diagnostic
	// will show up. This allows us to assume that values are valid later in
	// code.
	//
	// When a default value - and no type - is passed in the variable
	// declaration, the type of the default variable will be used. This will
	// allow to ensure that users set this variable correctly.
	Type cty.Type
	// Common name of the variable
	Name string
	// Description of the variable
	Description string
	// When Sensitive is set to true Packer will try it best to hide/obfuscate
	// the variable from the output stream. By replacing the text.
	Sensitive bool

	block *hcl.Block
}

func (v *Variable) GoString() string {
	return fmt.Sprintf("{Type:%q,CmdValue:%q,VarfileValue:%q,EnvValue:%q,DefaultValue:%q}",
		v.Type.GoString(), v.CmdValue.GoString(), v.VarfileValue.GoString(), v.EnvValue.GoString(), v.DefaultValue.GoString())
}

func (v *Variable) Value() (cty.Value, *hcl.Diagnostic) {
	for _, value := range []cty.Value{
		v.CmdValue,
		v.VarfileValue,
		v.EnvValue,
		v.DefaultValue,
	} {
		if !value.IsNull() {
			return value, nil
		}
	}

	return cty.UnknownVal(v.Type), &hcl.Diagnostic{
		Severity: hcl.DiagError,
		Summary:  fmt.Sprintf("Unset variable %q", v.Name),
		Detail: "A used variable must be set or have a default value; see " +
			"https://packer.io/docs/configuration/from-1.5/syntax.html for details.",
		Context: v.block.DefRange.Ptr(),
	}
}

type Variables map[string]*Variable

func (variables Variables) Values() (map[string]cty.Value, hcl.Diagnostics) {
	res := map[string]cty.Value{}
	var diags hcl.Diagnostics
	for k, v := range variables {
		var diag *hcl.Diagnostic
		res[k], diag = v.Value()
		if diag != nil {
			diags = append(diags, diag)
		}
	}
	return res, diags
}

// decodeConfig decodes a "variables" section the way packer 1 used to
func (variables *Variables) decodeConfigMap(block *hcl.Block, ectx *hcl.EvalContext) hcl.Diagnostics {
	if (*variables) == nil {
		(*variables) = Variables{}
	}
	attrs, diags := block.Body.JustAttributes()

	if diags.HasErrors() {
		return diags
	}

	for key, attr := range attrs {
		if _, found := (*variables)[key]; found {
			diags = append(diags, &hcl.Diagnostic{
				Severity: hcl.DiagError,
				Summary:  "Duplicate variable",
				Detail:   "Duplicate " + key + " variable definition found.",
				Subject:  attr.NameRange.Ptr(),
				Context:  block.DefRange.Ptr(),
			})
			continue
		}
		value, moreDiags := attr.Expr.Value(ectx)
		diags = append(diags, moreDiags...)
		if moreDiags.HasErrors() {
			continue
		}
		(*variables)[key] = &Variable{
			Name:         key,
			DefaultValue: value,
			Type:         value.Type(),
			block:        block,
		}
	}

	return diags
}

// decodeConfig decodes a "variables" section the way packer 1 used to
func (variables *Variables) decodeConfig(block *hcl.Block, ectx *hcl.EvalContext) hcl.Diagnostics {
	if (*variables) == nil {
		(*variables) = Variables{}
	}

	if _, found := (*variables)[block.Labels[0]]; found {

		return []*hcl.Diagnostic{{
			Severity: hcl.DiagError,
			Summary:  "Duplicate variable",
			Detail:   "Duplicate " + block.Labels[0] + " variable definition found.",
			Context:  block.DefRange.Ptr(),
		}}
	}

	var b struct {
		Description string   `hcl:"description,optional"`
		Sensitive   bool     `hcl:"sensitive,optional"`
		Rest        hcl.Body `hcl:",remain"`
	}
	diags := gohcl.DecodeBody(block.Body, nil, &b)

	if diags.HasErrors() {
		return diags
	}

	name := block.Labels[0]

	res := &Variable{
		Name:        name,
		Description: b.Description,
		Sensitive:   b.Sensitive,
		block:       block,
	}

	attrs, moreDiags := b.Rest.JustAttributes()
	diags = append(diags, moreDiags...)

	if t, ok := attrs["type"]; ok {
		delete(attrs, "type")
		tp, moreDiags := typeexpr.Type(t.Expr)
		diags = append(diags, moreDiags...)
		if moreDiags.HasErrors() {
			return diags
		}

		res.Type = tp
		delete(attrs, "type")
	}

	if def, ok := attrs["default"]; ok {
		delete(attrs, "default")
		defaultValue, moreDiags := def.Expr.Value(ectx)
		diags = append(diags, moreDiags...)
		if moreDiags.HasErrors() {
			return diags
		}

		if res.Type != cty.NilType {
			var err error
			defaultValue, err = convert.Convert(defaultValue, res.Type)
			if err != nil {
				diags = append(diags, &hcl.Diagnostic{
					Severity: hcl.DiagError,
					Summary:  "Invalid default value for variable",
					Detail:   fmt.Sprintf("This default value is not compatible with the variable's type constraint: %s.", err),
					Subject:  def.Expr.Range().Ptr(),
				})
				defaultValue = cty.DynamicVal
			}
		}

		res.DefaultValue = defaultValue
	}
	if len(attrs) > 0 {
		keys := []string{}
		for k := range attrs {
			keys = append(keys, k)
		}
		diags = append(diags, &hcl.Diagnostic{
			Severity: hcl.DiagWarning,
			Summary:  "Unknown keys",
			Detail:   fmt.Sprintf("unknown variable setting(s): %s", keys),
			Context:  block.DefRange.Ptr(),
		})
	}

	(*variables)[name] = res

	return diags
}

// Prefix your environment variables with VarEnvPrefix so that Packer can see
// them.
const VarEnvPrefix = "PKR_VAR_"

func (variables Variables) collectVariableValues(env []string, files []*hcl.File, argv map[string]string) hcl.Diagnostics {
	var diags hcl.Diagnostics

	for _, raw := range env {
		if !strings.HasPrefix(raw, VarEnvPrefix) {
			continue
		}
		raw = raw[len(VarEnvPrefix):] // trim the prefix

		eq := strings.Index(raw, "=")
		if eq == -1 {
			// Seems invalid, so we'll ignore it.
			continue
		}

		name := raw[:eq]
		value := raw[eq+1:]

		variable, found := variables[name]
		if !found {
			// this variable was not defined in the hcl files, let's skip it !
			continue
		}

		fakeFilename := fmt.Sprintf("<value for var.%s from env>", name)
		expr, moreDiags := hclsyntax.ParseExpression([]byte(value), fakeFilename, hcl.Pos{Line: 1, Column: 1})
		diags = append(diags, moreDiags...)
		if moreDiags.HasErrors() {
			continue
		}
		val, valDiags := expr.Value(nil)
		diags = append(diags, valDiags...)

		if variable.Type != cty.NilType {
			var err error
			val, err = convert.Convert(val, variable.Type)
			if err != nil {
				diags = append(diags, &hcl.Diagnostic{
					Severity: hcl.DiagError,
					Summary:  "Invalid value for variable",
					Detail:   fmt.Sprintf("The value for %s is not compatible with the variable's type constraint: %s.", name, err),
					Subject:  expr.Range().Ptr(),
				})
				val = cty.DynamicVal
			}
		}

		variable.EnvValue = val
	}

	// files will contain files found in the folder then files passed as
	// arguments.
	for _, file := range files {
		// Before we do our real decode, we'll probe to see if there are any
		// blocks of type "variable" in this body, since it's a common mistake
		// for new users to put variable declarations in pkrvars rather than
		// variable value definitions, and otherwise our error message for that
		// case is not so helpful.
		{
			content, _, _ := file.Body.PartialContent(&hcl.BodySchema{
				Blocks: []hcl.BlockHeaderSchema{
					{
						Type:       "variable",
						LabelNames: []string{"name"},
					},
				},
			})
			for _, block := range content.Blocks {
				name := block.Labels[0]
				diags = diags.Append(&hcl.Diagnostic{
					Severity: hcl.DiagError,
					Summary:  "Variable declaration in a .pkrvar file",
					Detail: fmt.Sprintf("A .pkrvar file is used to assign "+
						"values to variables that have already been declared "+
						"in .pkr files, not to declare new variables. To "+
						"declare variable %q, place this block in one of your"+
						" .pkr files,such as variables.pkr.hcl\n\nTo set a "+
						"value for this variable in %s, use the definition "+
						"syntax instead:\n    %s = <value>",
						name, block.TypeRange.Filename, name),
					Subject: &block.TypeRange,
				})
			}
			if diags.HasErrors() {
				// If we already found problems then JustAttributes below will find
				// the same problems with less-helpful messages, so we'll bail for
				// now to let the user focus on the immediate problem.
				return diags
			}
		}

		attrs, moreDiags := file.Body.JustAttributes()
		diags = append(diags, moreDiags...)

		for name, attr := range attrs {
			variable, found := variables[name]
			if !found {
				// No file defines this variable; let's skip it
				continue
			}

			val, moreDiags := attr.Expr.Value(nil)
			diags = append(diags, moreDiags...)

			if variable.Type != cty.NilType {
				var err error
				val, err = convert.Convert(val, variable.Type)
				if err != nil {
					diags = append(diags, &hcl.Diagnostic{
						Severity: hcl.DiagError,
						Summary:  "Invalid value for variable",
						Detail:   fmt.Sprintf("The value for %s is not compatible with the variable's type constraint: %s.", name, err),
						Subject:  attr.Expr.Range().Ptr(),
					})
					val = cty.DynamicVal
				}
			}

			variable.VarfileValue = val
		}
	}

	// Finally we process values given explicitly on the command line.
	for name, value := range argv {
		variable, found := variables[name]
		if !found {
			diags = append(diags, &hcl.Diagnostic{
				Severity: hcl.DiagWarning,
				Summary:  "Unknown -var variable",
				Detail: fmt.Sprintf("A %q variable was passed in the command "+
					"line but was not found in known variables."+
					"To declare variable %q, place this block in one of your"+
					" .pkr files,such as variables.pkr.hcl",
					name, name),
			})
			continue
		}

		fakeFilename := fmt.Sprintf("<value for var.%s from arguments>", name)
		expr, moreDiags := hclsyntax.ParseExpression([]byte(value), fakeFilename, hcl.Pos{Line: 1, Column: 1})
		diags = append(diags, moreDiags...)
		if moreDiags.HasErrors() {
			continue
		}
		val, valDiags := expr.Value(nil)
		diags = append(diags, valDiags...)

		if variable.Type != cty.NilType {
			var err error
			val, err = convert.Convert(val, variable.Type)
			if err != nil {
				diags = append(diags, &hcl.Diagnostic{
					Severity: hcl.DiagError,
					Summary:  "Invalid argument value for -var variable",
					Detail:   fmt.Sprintf("The received arg value for %s is not compatible with the variable's type constraint: %s.", name, err),
					Subject:  expr.Range().Ptr(),
				})
				val = cty.DynamicVal
			}
		}

		variable.CmdValue = val
	}

	return diags
}