// Copyright IBM Corp. 2024, 2025
// SPDX-License-Identifier: BUSL-1.1

package hcl2template

import (
	"bytes"
	"encoding/base64"

	"github.com/hashicorp/go-cty-funcs/cidr"
	"github.com/hashicorp/go-cty-funcs/collection"
	"github.com/hashicorp/go-cty-funcs/crypto"
	"github.com/hashicorp/go-cty-funcs/encoding"
	"github.com/hashicorp/go-cty-funcs/filesystem"
	"github.com/hashicorp/go-cty-funcs/uuid"
	"github.com/hashicorp/hcl/v2/ext/tryfunc"
	"github.com/hashicorp/hcl/v2/ext/typeexpr"
	pkrfunction "github.com/hashicorp/packer/hcl2template/function"
	ctyyaml "github.com/zclconf/go-cty-yaml"
	"github.com/zclconf/go-cty/cty"
	"github.com/zclconf/go-cty/cty/function"
	"github.com/zclconf/go-cty/cty/function/stdlib"
	"golang.org/x/text/encoding/ianaindex"
)

// Functions returns the set of functions that should be used to when
// evaluating expressions in the receiving scope.
//
// basedir is used with file functions and allows a user to reference a file
// using local path. Usually basedir is the directory in which the config file
// is located
func Functions(basedir string) map[string]function.Function {

	funcs := map[string]function.Function{
		"abs":                    stdlib.AbsoluteFunc,
		"abspath":                filesystem.AbsPathFunc,
		"alltrue":                pkrfunction.AllTrue,
		"anytrue":                pkrfunction.AnyTrue,
		"aws_secretsmanager":     pkrfunction.AWSSecret,
		"aws_secretsmanager_raw": pkrfunction.AWSSecretRaw,
		"basename":               filesystem.BasenameFunc,
		"base64decode":           encoding.Base64DecodeFunc,
		"base64encode":           encoding.Base64EncodeFunc,
		"base64gzip":             pkrfunction.Base64GzipFunc,
		"bcrypt":                 crypto.BcryptFunc,
		"can":                    tryfunc.CanFunc,
		"ceil":                   stdlib.CeilFunc,
		"chomp":                  stdlib.ChompFunc,
		"chunklist":              stdlib.ChunklistFunc,
		"cidrhost":               cidr.HostFunc,
		"cidrnetmask":            cidr.NetmaskFunc,
		"cidrsubnet":             cidr.SubnetFunc,
		"cidrsubnets":            cidr.SubnetsFunc,
		"coalesce":               collection.CoalesceFunc,
		"coalescelist":           stdlib.CoalesceListFunc,
		"compact":                stdlib.CompactFunc,
		"concat":                 stdlib.ConcatFunc,
		"consul_key":             pkrfunction.ConsulFunc,
		"contains":               stdlib.ContainsFunc,
		"convert":                typeexpr.ConvertFunc,
		"csvdecode":              stdlib.CSVDecodeFunc,
		"dirname":                filesystem.DirnameFunc,
		"distinct":               stdlib.DistinctFunc,
		"element":                stdlib.ElementFunc,
		"endswith":               pkrfunction.EndsWithFunc,
		"file":                   filesystem.MakeFileFunc(basedir, false),
		"filebase64":             pkrfunction.Filebase64,
		"fileexists":             filesystem.MakeFileExistsFunc(basedir),
		"fileset":                filesystem.MakeFileSetFunc(basedir),
		"flatten":                stdlib.FlattenFunc,
		"floor":                  stdlib.FloorFunc,
		"format":                 stdlib.FormatFunc,
		"formatdate":             stdlib.FormatDateFunc,
		"formatlist":             stdlib.FormatListFunc,
		"indent":                 stdlib.IndentFunc,
		"index":                  pkrfunction.IndexFunc, // stdlib.IndexFunc is not compatible
		"join":                   stdlib.JoinFunc,
		"jsondecode":             stdlib.JSONDecodeFunc,
		"jsonencode":             stdlib.JSONEncodeFunc,
		"keys":                   stdlib.KeysFunc,
		"legacy_isotime":         pkrfunction.LegacyIsotimeFunc,
		"legacy_strftime":        pkrfunction.LegacyStrftimeFunc,
		"length":                 pkrfunction.LengthFunc,
		"log":                    stdlib.LogFunc,
		"lookup":                 stdlib.LookupFunc,
		"lower":                  stdlib.LowerFunc,
		"max":                    stdlib.MaxFunc,
		"md5":                    crypto.Md5Func,
		"merge":                  stdlib.MergeFunc,
		"min":                    stdlib.MinFunc,
		"parseint":               stdlib.ParseIntFunc,
		"pathexpand":             filesystem.PathExpandFunc,
		"pow":                    stdlib.PowFunc,
		"range":                  stdlib.RangeFunc,
		"reverse":                stdlib.ReverseListFunc,
		"replace":                stdlib.ReplaceFunc,
		"regex":                  stdlib.RegexFunc,
		"regexall":               stdlib.RegexAllFunc,
		"regex_replace":          stdlib.RegexReplaceFunc,
		"rsadecrypt":             crypto.RsaDecryptFunc,
		"setintersection":        stdlib.SetIntersectionFunc,
		"setproduct":             stdlib.SetProductFunc,
		"setunion":               stdlib.SetUnionFunc,
		"sha1":                   crypto.Sha1Func,
		"sha256":                 crypto.Sha256Func,
		"sha512":                 crypto.Sha512Func,
		"signum":                 stdlib.SignumFunc,
		"slice":                  stdlib.SliceFunc,
		"sort":                   stdlib.SortFunc,
		"split":                  stdlib.SplitFunc,
		"startswith":             pkrfunction.StartsWithFunc,
		"strcontains":            pkrfunction.StrContains,
		"strrev":                 stdlib.ReverseFunc,
		"substr":                 stdlib.SubstrFunc,
		"sum":                    pkrfunction.SumFunc,
		"textdecodebase64":       TextDecodeBase64Func,
		"textencodebase64":       TextEncodeBase64Func,
		"timestamp":              pkrfunction.TimestampFunc,
		"timeadd":                stdlib.TimeAddFunc,
		"title":                  stdlib.TitleFunc,
		"trim":                   stdlib.TrimFunc,
		"trimprefix":             stdlib.TrimPrefixFunc,
		"trimspace":              stdlib.TrimSpaceFunc,
		"trimsuffix":             stdlib.TrimSuffixFunc,
		"try":                    tryfunc.TryFunc,
		"upper":                  stdlib.UpperFunc,
		"urlencode":              encoding.URLEncodeFunc,
		"uuidv4":                 uuid.V4Func,
		"uuidv5":                 uuid.V5Func,
		"values":                 stdlib.ValuesFunc,
		"vault":                  pkrfunction.VaultFunc,
		"yamldecode":             ctyyaml.YAMLDecodeFunc,
		"yamlencode":             ctyyaml.YAMLEncodeFunc,
		"zipmap":                 stdlib.ZipmapFunc,
	}

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

	return funcs
}

// TextEncodeBase64Func constructs a function that encodes a string to a target encoding and then to a base64 sequence.
var TextEncodeBase64Func = function.New(&function.Spec{
	Params: []function.Parameter{
		{
			Name: "string",
			Type: cty.String,
		},
		{
			Name: "encoding",
			Type: cty.String,
		},
	},
	Description:  "Encodes the input string (UTF-8) to the destination encoding. The output is base64 to account for cty limiting strings to NFC normalised UTF-8 strings.",
	Type:         function.StaticReturnType(cty.String),
	RefineResult: func(rb *cty.RefinementBuilder) *cty.RefinementBuilder { return rb.NotNull() },
	Impl: func(args []cty.Value, retType cty.Type) (cty.Value, error) {
		encoding, err := ianaindex.IANA.Encoding(args[1].AsString())
		if err != nil || encoding == nil {
			return cty.UnknownVal(cty.String), function.NewArgErrorf(1, "%q is not a supported IANA encoding name or alias", args[1].AsString())
		}

		encName, err := ianaindex.IANA.Name(encoding)
		if err != nil { // would be weird, since we just read this encoding out
			encName = args[1].AsString()
		}

		encoder := encoding.NewEncoder()
		encodedInput, err := encoder.Bytes([]byte(args[0].AsString()))
		if err != nil {
			// The string representations of "err" disclose implementation
			// details of the underlying library, and the main error we might
			// like to return a special message for is unexported as
			// golang.org/x/text/encoding/internal.RepertoireError, so this
			// is just a generic error message for now.
			//
			// We also don't include the string itself in the message because
			// it can typically be very large, contain newline characters,
			// etc.
			return cty.UnknownVal(cty.String), function.NewArgErrorf(0, "the given string contains characters that cannot be represented in %s", encName)
		}

		return cty.StringVal(base64.StdEncoding.EncodeToString(encodedInput)), nil
	},
})

// TextDecodeBase64Func constructs a function that decodes a base64 sequence from the source encoding to UTF-8.
var TextDecodeBase64Func = function.New(&function.Spec{
	Params: []function.Parameter{
		{
			Name: "source",
			Type: cty.String,
		},
		{
			Name: "encoding",
			Type: cty.String,
		},
	},
	Type:         function.StaticReturnType(cty.String),
	Description:  "Encodes the input base64 blob from an encoding to utf-8. The input is base64 to account for cty limiting strings to NFC normalised UTF-8 strings.",
	RefineResult: func(rb *cty.RefinementBuilder) *cty.RefinementBuilder { return rb.NotNull() },
	Impl: func(args []cty.Value, retType cty.Type) (cty.Value, error) {
		encoding, err := ianaindex.IANA.Encoding(args[1].AsString())
		if err != nil || encoding == nil {
			return cty.UnknownVal(cty.String), function.NewArgErrorf(1, "%q is not a supported IANA encoding name or alias", args[1].AsString())
		}

		encName, err := ianaindex.IANA.Name(encoding)
		if err != nil { // would be weird, since we just read this encoding out
			encName = args[1].AsString()
		}

		s := args[0].AsString()
		sDec, err := base64.StdEncoding.DecodeString(s)
		if err != nil {
			switch err := err.(type) {
			case base64.CorruptInputError:
				return cty.UnknownVal(cty.String), function.NewArgErrorf(0, "the given value is has an invalid base64 symbol at offset %d", int(err))
			default:
				return cty.UnknownVal(cty.String), function.NewArgErrorf(0, "invalid source string: %w", err)
			}
		}

		decoder := encoding.NewDecoder()
		decoded, err := decoder.Bytes(sDec)
		if err != nil || bytes.ContainsRune(decoded, '�') {
			return cty.UnknownVal(cty.String), function.NewArgErrorf(0, "the given string contains symbols that are not defined for %s", encName)
		}

		return cty.StringVal(string(decoded)), nil
	},
})
