package lang

import (
	"fmt"

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

	"github.com/hashicorp/terraform/lang/funcs"
)

var impureFunctions = []string{
	"bcrypt",
	"timestamp",
	"uuid",
}

// Functions returns the set of functions that should be used to when evaluating
// expressions in the receiving scope.
func (s *Scope) Functions() map[string]function.Function {
	s.funcsLock.Lock()
	if s.funcs == nil {
		// Some of our functions are just directly the cty stdlib functions.
		// Others are implemented in the subdirectory "funcs" here in this
		// repository. New functions should generally start out their lives
		// in the "funcs" directory and potentially graduate to cty stdlib
		// later if the functionality seems to be something domain-agnostic
		// that would be useful to all applications using cty functions.

		s.funcs = map[string]function.Function{
			"abs":             stdlib.AbsoluteFunc,
			"basename":        funcs.BasenameFunc,
			"base64decode":    funcs.Base64DecodeFunc,
			"base64encode":    funcs.Base64EncodeFunc,
			"base64gzip":      funcs.Base64GzipFunc,
			"base64sha256":    funcs.Base64Sha256Func,
			"base64sha512":    funcs.Base64Sha512Func,
			"bcrypt":          funcs.BcryptFunc,
			"ceil":            funcs.CeilFunc,
			"chomp":           funcs.ChompFunc,
			"cidrhost":        funcs.CidrHostFunc,
			"cidrnetmask":     funcs.CidrNetmaskFunc,
			"cidrsubnet":      funcs.CidrSubnetFunc,
			"coalesce":        stdlib.CoalesceFunc,
			"coalescelist":    funcs.CoalesceListFunc,
			"compact":         funcs.CompactFunc,
			"concat":          stdlib.ConcatFunc,
			"contains":        funcs.ContainsFunc,
			"csvdecode":       stdlib.CSVDecodeFunc,
			"dirname":         funcs.DirnameFunc,
			"distinct":        funcs.DistinctFunc,
			"element":         funcs.ElementFunc,
			"chunklist":       funcs.ChunklistFunc,
			"file":            funcs.MakeFileFunc(s.BaseDir, false),
			"fileexists":      funcs.MakeFileExistsFunc(s.BaseDir),
			"filebase64":      funcs.MakeFileFunc(s.BaseDir, true),
			"flatten":         funcs.FlattenFunc,
			"floor":           funcs.FloorFunc,
			"format":          stdlib.FormatFunc,
			"formatdate":      stdlib.FormatDateFunc,
			"formatlist":      stdlib.FormatListFunc,
			"indent":          funcs.IndentFunc,
			"index":           funcs.IndexFunc,
			"join":            funcs.JoinFunc,
			"jsondecode":      stdlib.JSONDecodeFunc,
			"jsonencode":      stdlib.JSONEncodeFunc,
			"keys":            funcs.KeysFunc,
			"length":          funcs.LengthFunc,
			"list":            funcs.ListFunc,
			"log":             funcs.LogFunc,
			"lookup":          funcs.LookupFunc,
			"lower":           stdlib.LowerFunc,
			"map":             funcs.MapFunc,
			"matchkeys":       funcs.MatchkeysFunc,
			"max":             stdlib.MaxFunc,
			"md5":             funcs.Md5Func,
			"merge":           funcs.MergeFunc,
			"min":             stdlib.MinFunc,
			"pathexpand":      funcs.PathExpandFunc,
			"pow":             funcs.PowFunc,
			"replace":         funcs.ReplaceFunc,
			"rsadecrypt":      funcs.RsaDecryptFunc,
			"sethaselement":   stdlib.SetHasElementFunc,
			"setintersection": stdlib.SetIntersectionFunc,
			"setproduct":      funcs.SetProductFunc,
			"setunion":        stdlib.SetUnionFunc,
			"sha1":            funcs.Sha1Func,
			"sha256":          funcs.Sha256Func,
			"sha512":          funcs.Sha512Func,
			"signum":          funcs.SignumFunc,
			"slice":           funcs.SliceFunc,
			"sort":            funcs.SortFunc,
			"split":           funcs.SplitFunc,
			"substr":          stdlib.SubstrFunc,
			"timestamp":       funcs.TimestampFunc,
			"timeadd":         funcs.TimeAddFunc,
			"title":           funcs.TitleFunc,
			"tostring":        funcs.MakeToFunc(cty.String),
			"tonumber":        funcs.MakeToFunc(cty.Number),
			"tobool":          funcs.MakeToFunc(cty.Bool),
			"toset":           funcs.MakeToFunc(cty.Set(cty.DynamicPseudoType)),
			"tolist":          funcs.MakeToFunc(cty.List(cty.DynamicPseudoType)),
			"tomap":           funcs.MakeToFunc(cty.Map(cty.DynamicPseudoType)),
			"transpose":       funcs.TransposeFunc,
			"trimspace":       funcs.TrimSpaceFunc,
			"upper":           stdlib.UpperFunc,
			"urlencode":       funcs.URLEncodeFunc,
			"uuid":            funcs.UUIDFunc,
			"values":          funcs.ValuesFunc,
			"zipmap":          funcs.ZipmapFunc,
		}

		s.funcs["templatefile"] = funcs.MakeTemplateFileFunc(s.BaseDir, func() map[string]function.Function {
			// The templatefile function prevents recursive calls to itself
			// by copying this map and overwriting the "templatefile" entry.
			return s.funcs
		})

		if s.PureOnly {
			// Force our few impure functions to return unknown so that we
			// can defer evaluating them until a later pass.
			for _, name := range impureFunctions {
				s.funcs[name] = function.Unpredictable(s.funcs[name])
			}
		}
	}
	s.funcsLock.Unlock()

	return s.funcs
}

var unimplFunc = function.New(&function.Spec{
	Type: func([]cty.Value) (cty.Type, error) {
		return cty.DynamicPseudoType, fmt.Errorf("function not yet implemented")
	},
	Impl: func([]cty.Value, cty.Type) (cty.Value, error) {
		return cty.DynamicVal, fmt.Errorf("function not yet implemented")
	},
})