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"
)

var impureFunctions = []string{
	"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 {
		s.funcs = map[string]function.Function{
			"abs":          stdlib.AbsoluteFunc,
			"basename":     unimplFunc, // TODO
			"base64decode": unimplFunc, // TODO
			"base64encode": unimplFunc, // TODO
			"base64gzip":   unimplFunc, // TODO
			"base64sha256": unimplFunc, // TODO
			"base64sha512": unimplFunc, // TODO
			"bcrypt":       unimplFunc, // TODO
			"ceil":         unimplFunc, // TODO
			"chomp":        unimplFunc, // TODO
			"cidrhost":     unimplFunc, // TODO
			"cidrnetmask":  unimplFunc, // TODO
			"cidrsubnet":   unimplFunc, // TODO
			"coalesce":     stdlib.CoalesceFunc,
			"coalescelist": unimplFunc, // TODO
			"compact":      unimplFunc, // TODO
			"concat":       stdlib.ConcatFunc,
			"contains":     unimplFunc, // TODO
			"csvdecode":    stdlib.CSVDecodeFunc,
			"dirname":      unimplFunc, // TODO
			"distinct":     unimplFunc, // TODO
			"element":      unimplFunc, // TODO
			"chunklist":    unimplFunc, // TODO
			"file":         unimplFunc, // TODO
			"matchkeys":    unimplFunc, // TODO
			"flatten":      unimplFunc, // TODO
			"floor":        unimplFunc, // TODO
			"format":       stdlib.FormatFunc,
			"formatlist":   stdlib.FormatListFunc,
			"indent":       unimplFunc, // TODO
			"index":        unimplFunc, // TODO
			"join":         unimplFunc, // TODO
			"jsondecode":   stdlib.JSONDecodeFunc,
			"jsonencode":   stdlib.JSONEncodeFunc,
			"length":       unimplFunc, // TODO
			"list":         unimplFunc, // TODO
			"log":          unimplFunc, // TODO
			"lower":        stdlib.LowerFunc,
			"map":          unimplFunc, // TODO
			"max":          stdlib.MaxFunc,
			"md5":          unimplFunc, // TODO
			"merge":        unimplFunc, // TODO
			"min":          stdlib.MinFunc,
			"pathexpand":   unimplFunc, // TODO
			"pow":          unimplFunc, // TODO
			"replace":      unimplFunc, // TODO
			"rsadecrypt":   unimplFunc, // TODO
			"sha1":         unimplFunc, // TODO
			"sha256":       unimplFunc, // TODO
			"sha512":       unimplFunc, // TODO
			"signum":       unimplFunc, // TODO
			"slice":        unimplFunc, // TODO
			"sort":         unimplFunc, // TODO
			"split":        unimplFunc, // TODO
			"substr":       stdlib.SubstrFunc,
			"timestamp":    unimplFunc, // TODO
			"timeadd":      unimplFunc, // TODO
			"title":        unimplFunc, // TODO
			"transpose":    unimplFunc, // TODO
			"trimspace":    unimplFunc, // TODO
			"upper":        stdlib.UpperFunc,
			"urlencode":    unimplFunc, // TODO
			"uuid":         unimplFunc, // TODO
			"zipmap":       unimplFunc, // TODO
		}

		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")
	},
})