// Copyright 2026 Versity Software
// This file is licensed under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

package policy

import (
	"bytes"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"net"
	"regexp"
	"strconv"
	"strings"
	"time"

	"github.com/versity/versitygw/debuglogger"
)

// ConditionValues decodes the value(s) of a single Condition operator/key
// pair. Unlike Action/Resource's string-only StringOrSlice, a Condition
// value may also be a bare JSON number or boolean rather than
// being re-serialized, so e.g. "5.50" round-trips as "5.50", not "5.5". A
// JSON null value or a non-scalar (object/array) element is rejected.
type ConditionValues []string

func (c *ConditionValues) UnmarshalJSON(data []byte) error {
	trimmed := bytes.TrimSpace(data)
	if len(trimmed) > 0 && trimmed[0] == '[' {
		var raws []json.RawMessage
		if err := json.Unmarshal(trimmed, &raws); err != nil {
			return err
		}
		values := make([]string, len(raws))
		for i, r := range raws {
			s, ok := decodeConditionScalar(r)
			if !ok {
				return fmt.Errorf("policy: invalid condition value %s", r)
			}
			values[i] = s
		}
		*c = values
		return nil
	}

	s, ok := decodeConditionScalar(trimmed)
	if !ok {
		return fmt.Errorf("policy: invalid condition value %s", trimmed)
	}
	*c = ConditionValues{s}
	return nil
}

// decodeConditionScalar decodes a single JSON scalar (string, number, or
// bool) to its string form, rejecting null and any non-scalar (object,
// array) value.
func decodeConditionScalar(raw json.RawMessage) (string, bool) {
	trimmed := bytes.TrimSpace(raw)
	if len(trimmed) == 0 {
		return "", false
	}
	if trimmed[0] == '"' {
		var s string
		if err := json.Unmarshal(trimmed, &s); err != nil {
			return "", false
		}
		return s, true
	}
	switch string(trimmed) {
	case "true", "false":
		return string(trimmed), true
	case "null":
		return "", false
	}
	var num json.Number
	if err := json.Unmarshal(trimmed, &num); err != nil {
		return "", false
	}
	return num.String(), true
}

// conditionQualifier is IAM's multivalued-context-key set operator, given as
// a "ForAllValues:"/"ForAnyValue:" prefix on a condition operator name.
type conditionQualifier int

const (
	qualifierNone conditionQualifier = iota
	qualifierForAllValues
	qualifierForAnyValue
)

// conditionComparator is a single (policy value, request value) match test
// for one condition operator family, e.g. string equality or a numeric
// comparison. It never itself accounts for absence, IfExists, negation, or
// multivalued aggregation - those are handled by evaluateConditionKey and
// aggregate around it.
type conditionComparator func(expected, actual string) bool

// conditionOperatorDef is a recognized condition operator's evaluation
// behavior: negate distinguishes a Not-family operator (StringNotEquals,
// ArnNotEquals, ...) from its positive counterpart - both share the same
// comparator, since "not equal" is just the equality test used differently
// (see aggregate), not a different comparison.
type conditionOperatorDef struct {
	compare conditionComparator
	negate  bool
}

// conditionRegistry is every condition operator base name this package
// recognizes, except "Null" (handled separately by evaluateNull - it has no
// value comparator at all, only a presence check). Populated below from
// AWS's documented condition operator reference.
var conditionRegistry = map[string]conditionOperatorDef{
	"StringEquals":              {compare: stringExact},
	"StringNotEquals":           {compare: stringExact, negate: true},
	"StringEqualsIgnoreCase":    {compare: stringFold},
	"StringNotEqualsIgnoreCase": {compare: stringFold, negate: true},
	"StringLike":                {compare: stringLike},
	"StringNotLike":             {compare: stringLike, negate: true},

	"NumericEquals":            {compare: numericCompare(func(a, e float64) bool { return a == e })},
	"NumericNotEquals":         {compare: numericCompare(func(a, e float64) bool { return a == e }), negate: true},
	"NumericLessThan":          {compare: numericCompare(func(a, e float64) bool { return a < e })},
	"NumericLessThanEquals":    {compare: numericCompare(func(a, e float64) bool { return a <= e })},
	"NumericGreaterThan":       {compare: numericCompare(func(a, e float64) bool { return a > e })},
	"NumericGreaterThanEquals": {compare: numericCompare(func(a, e float64) bool { return a >= e })},

	"DateEquals":            {compare: dateCompare(func(a, e time.Time) bool { return a.Equal(e) })},
	"DateNotEquals":         {compare: dateCompare(func(a, e time.Time) bool { return a.Equal(e) }), negate: true},
	"DateLessThan":          {compare: dateCompare(func(a, e time.Time) bool { return a.Before(e) })},
	"DateLessThanEquals":    {compare: dateCompare(func(a, e time.Time) bool { return !a.After(e) })},
	"DateGreaterThan":       {compare: dateCompare(func(a, e time.Time) bool { return a.After(e) })},
	"DateGreaterThanEquals": {compare: dateCompare(func(a, e time.Time) bool { return !a.Before(e) })},

	"Bool": {compare: boolMatch},

	"BinaryEquals": {compare: binaryMatch},

	// ArnEquals and ArnLike behave identically in real AWS (both wildcard
	// -aware), and are matched here with the same whole-string globMatch
	// already used for Action/Resource - do not "fix" ArnEquals to a strict
	// == later, that would diverge from AWS behavior.
	"ArnEquals":    {compare: stringLike},
	"ArnLike":      {compare: stringLike},
	"ArnNotEquals": {compare: stringLike, negate: true},
	"ArnNotLike":   {compare: stringLike, negate: true},

	"IpAddress":    {compare: ipMatch},
	"NotIpAddress": {compare: ipMatch, negate: true},
}

func stringExact(expected, actual string) bool { return expected == actual }
func stringFold(expected, actual string) bool  { return strings.EqualFold(expected, actual) }
func stringLike(expected, actual string) bool  { return globMatch(expected, actual) }

// numericCompare builds a comparator from a (actual, expected float64) ->
// bool test, matching AWS's direction convention (the request's value is
// compared against the policy's value). Either operand failing to parse as
// a number fails the comparison rather than erroring
func numericCompare(op func(actual, expected float64) bool) conditionComparator {
	return func(expected, actual string) bool {
		e, eerr := strconv.ParseFloat(expected, 64)
		a, aerr := strconv.ParseFloat(actual, 64)
		return eerr == nil && aerr == nil && op(a, e)
	}
}

// dateCompare builds a comparator from a (actual, expected time.Time) ->
// bool test, same direction convention as numericCompare.
func dateCompare(op func(actual, expected time.Time) bool) conditionComparator {
	return func(expected, actual string) bool {
		e, eok := parseConditionDate(expected)
		a, aok := parseConditionDate(actual)
		return eok && aok && op(a, e)
	}
}

// parseConditionDate parses a Date condition operand in either form AWS
// accepts: an RFC 3339 date-time, or Unix epoch seconds (optionally
// fractional).
func parseConditionDate(s string) (time.Time, bool) {
	if t, err := time.Parse(time.RFC3339, s); err == nil {
		return t, true
	}
	if t, err := time.Parse(time.RFC3339Nano, s); err == nil {
		return t, true
	}
	if f, err := strconv.ParseFloat(s, 64); err == nil {
		sec := int64(f)
		nsec := int64((f - float64(sec)) * 1e9)
		return time.Unix(sec, nsec).UTC(), true
	}
	return time.Time{}, false
}

func boolMatch(expected, actual string) bool {
	e, eerr := strconv.ParseBool(expected)
	a, aerr := strconv.ParseBool(actual)
	return eerr == nil && aerr == nil && e == a
}

func binaryMatch(expected, actual string) bool {
	e, eerr := base64.StdEncoding.DecodeString(expected)
	a, aerr := base64.StdEncoding.DecodeString(actual)
	return eerr == nil && aerr == nil && bytes.Equal(e, a)
}

// ipMatch reports whether actual (an address) falls within cidr (a CIDR
// range, or an exact address treated as a /32 or /128), matching IAM's
// IpAddress/NotIpAddress condition operators. An unparseable operand on
// either side never matches (fails closed) rather than erroring.
func ipMatch(cidr, actual string) bool {
	c := cidr
	if !strings.Contains(c, "/") {
		if ip := net.ParseIP(c); ip != nil && ip.To4() != nil {
			c += "/32"
		} else {
			c += "/128"
		}
	}
	_, network, err := net.ParseCIDR(c)
	if err != nil {
		return false
	}
	ip := net.ParseIP(actual)
	return ip != nil && network.Contains(ip)
}

// parsedOperator is a condition operator name decomposed into its set
// qualifier, base operator, and IfExists flag.
type parsedOperator struct {
	qualifier conditionQualifier
	base      string
	ifExists  bool
}

// parseOperatorName decomposes name (e.g. "ForAllValues:StringNotEqualsIfExists")
// into a parsedOperator, reporting ok=false if the base operator (after
// stripping a recognized qualifier prefix and IfExists suffix) isn't one
// conditionRegistry recognizes, or is "Null" (Null has no IfExists variant -
// "NullIfExists" is rejected here since after suffix-stripping "Null" isn't
// itself in conditionRegistry). A bare "Null", optionally qualifier-prefixed, is accepted
func parseOperatorName(name string) (parsedOperator, bool) {
	op := name
	qualifier := qualifierNone
	switch {
	case strings.HasPrefix(op, "ForAllValues:"):
		qualifier = qualifierForAllValues
		op = strings.TrimPrefix(op, "ForAllValues:")
	case strings.HasPrefix(op, "ForAnyValue:"):
		qualifier = qualifierForAnyValue
		op = strings.TrimPrefix(op, "ForAnyValue:")
	}

	if op == "Null" {
		return parsedOperator{qualifier: qualifier, base: "Null"}, true
	}

	base := strings.TrimSuffix(op, "IfExists")
	ifExists := base != op
	if _, ok := conditionRegistry[base]; !ok {
		return parsedOperator{}, false
	}
	return parsedOperator{qualifier: qualifier, base: base, ifExists: ifExists}, true
}

// conditionShapeValid checks raw (a statement's Condition block) against
// IAM's condition grammar for write-time validation: an object of operator
// -> (key -> value), where every operator name is recognized by
// parseOperatorName. An absent, null, or empty Condition is valid (matches
// evaluateCondition's "always matches" contract).
func conditionShapeValid(raw json.RawMessage) bool {
	if len(raw) == 0 || string(bytes.TrimSpace(raw)) == "null" {
		return true
	}
	var block map[string]map[string]ConditionValues
	if err := json.Unmarshal(raw, &block); err != nil {
		return false
	}
	for operator := range block {
		if _, ok := parseOperatorName(operator); !ok {
			return false
		}
	}
	return true
}

// conditionVariableOperators is the subset of conditionRegistry that AWS
// documents as supporting ${...} policy-variable substitution in a
// Condition value: the String family and the Arn family (both ultimately
// whole-string comparisons). AWS's policy-variable documentation
// specifically excludes Numeric, Date, Boolean, Binary, IP address, and
// Null operators - a variable placed there is never substituted, regardless
// of document version.
var conditionVariableOperators = map[string]bool{
	"StringEquals":              true,
	"StringNotEquals":           true,
	"StringEqualsIgnoreCase":    true,
	"StringNotEqualsIgnoreCase": true,
	"StringLike":                true,
	"StringNotLike":             true,
	"ArnEquals":                 true,
	"ArnLike":                   true,
	"ArnNotEquals":              true,
	"ArnNotLike":                true,
}

// evaluateCondition evaluates a policy statement's Condition block against
// ctxVars - a "<provider-url>:<claim>" keyed context for trust-policy
// evaluation, or an "aws:<GlobalKey>" keyed context for identity-policy
// evaluation. An absent or empty Condition always matches. version is the
// enclosing document's Version element: a ${...} policy variable in a
// Condition value is only ever substituted when version is exactly
// Version2012 AND the operator is one of conditionVariableOperators -
// AWS requires the 2012-10-17 policy version to use variables at all, and
// never expands them for Numeric/Date/Bool/Binary/IP/Null operators even
// then. A variable that doesn't qualify is left as literal text, the
// same fallback used for an absent/multivalued context key - so it simply
// won't match a real condition value, rather than silently expanding into
// something AWS itself wouldn't.
//
// matched reports whether the condition holds; ok reports whether it could
// be evaluated at all. ok is false only for a Condition block whose JSON
// shape or operator name conditionShapeValid would already reject - i.e.
// only for a document stored before that write-time validation existed, or
// containing a future operator this package doesn't yet recognize. Callers
// MUST treat ok=false as "cannot rule out a hidden Deny" and deny the whole
// evaluation, never as a non-match - see EvaluateIdentityPolicies and
// EvaluateWebIdentityTrust.
func evaluateCondition(raw json.RawMessage, ctxVars map[string][]string, version string) (matched bool, ok bool) {
	if len(raw) == 0 || string(bytes.TrimSpace(raw)) == "null" {
		return true, true
	}

	var block map[string]map[string]ConditionValues
	if err := json.Unmarshal(raw, &block); err != nil {
		debuglogger.Logf("policy condition block failed to parse: %v", err)
		return false, false
	}

	for operator, kvs := range block {
		op, recognized := parseOperatorName(operator)
		if !recognized {
			debuglogger.Logf("policy condition: unrecognized operator %q", operator)
			return false, false
		}
		for key, expected := range kvs {
			actual, present := lookupContextValues(ctxVars, key)
			if version == Version2012 && conditionVariableOperators[op.base] {
				expected = substituteConditionValues(expected, ctxVars)
			}
			if !evaluateConditionKey(op, expected, actual, present) {
				return false, true
			}
		}
	}
	return true, true
}

// lookupContextValues retrieves ctxVars[key], matching key
// case-insensitively: AWS documents condition (and policy-variable) key
// *names* as case-insensitive - "aws:SourceIp" and "AWS:SOURCEIP" name the
// same key - even though the values held under that key remain
// case-sensitive. An exact match is tried first so the common case doesn't
// pay for a map scan.
func lookupContextValues(ctxVars map[string][]string, key string) ([]string, bool) {
	if v, ok := ctxVars[key]; ok {
		return v, true
	}
	for k, v := range ctxVars {
		if strings.EqualFold(k, key) {
			return v, true
		}
	}
	return nil, false
}

// policyVariablePattern matches a single "${...}" policy-variable
// placeholder, e.g. "${aws:username}".
var policyVariablePattern = regexp.MustCompile(`\$\{([A-Za-z0-9_:.\-]+)\}`)

// substitutePolicyVariables replaces every ${key} placeholder in s with the
// single value ctxVars holds for key, looked up the same case-insensitive
// way as a Condition key. AWS only allows a single-valued context key to be
// used as a policy variable; a placeholder naming an absent or multivalued
// key is left as literal text, same as any other substring - so it simply
// won't match a real resource ARN or condition value, rather than being
// silently dropped and turning a Deny that relies on it into a no-op.
func substitutePolicyVariables(s string, ctxVars map[string][]string) string {
	if !strings.Contains(s, "${") {
		return s
	}
	return policyVariablePattern.ReplaceAllStringFunc(s, func(match string) string {
		key := match[2 : len(match)-1]
		values, ok := lookupContextValues(ctxVars, key)
		if !ok || len(values) != 1 {
			return match
		}
		return values[0]
	})
}

// substituteConditionValues applies substitutePolicyVariables to every
// element of values, so e.g. a Condition of
// {"StringEquals":{"iam:ResourceTag/owner":"${aws:username}"}} compares
// against the requester's own username rather than the literal text.
func substituteConditionValues(values ConditionValues, ctxVars map[string][]string) ConditionValues {
	out := make(ConditionValues, len(values))
	for i, v := range values {
		out[i] = substitutePolicyVariables(v, ctxVars)
	}
	return out
}

// evaluateConditionKey evaluates one operator/key pair of an already
// -parsed Condition block against actual (ctxVars[key]) and present
// (whether key was in ctxVars at all).
func evaluateConditionKey(op parsedOperator, expected ConditionValues, actual []string, present bool) bool {
	if op.base == "Null" {
		return evaluateNull(expected, present)
	}
	entry := conditionRegistry[op.base] // guaranteed present - parseOperatorName already validated op.base

	if op.qualifier == qualifierForAllValues && !present {
		return true
	}
	if entry.negate {
		if !present {
			return true
		}
		return aggregate(op.qualifier, true, expected, actual, entry.compare)
	}
	if !present {
		return op.ifExists
	}
	return aggregate(op.qualifier, false, expected, actual, entry.compare)
}

// evaluateNull implements the Null condition operator: true if expected
// (normally exactly one of "true"/"false", case-insensitive) says the key
// must be absent ("true") and it is, or must be present ("false") and it
// is. A value that's neither "true" nor "false" never satisfies the
// condition (fails closed)
func evaluateNull(expected ConditionValues, present bool) bool {
	for _, e := range expected {
		switch {
		case strings.EqualFold(e, "true"):
			if !present {
				return true
			}
		case strings.EqualFold(e, "false"):
			if present {
				return true
			}
		}
	}
	return false
}

// aggregate reports whether expected/actual satisfy a condition-key match
// under qualifier's multivalued-context-key semantics. negate selects the
// Not-operator family, sharing the same per-pair comparator as its positive
// counterpart (see conditionRegistry).
func aggregate(qualifier conditionQualifier, negate bool, expected ConditionValues, actual []string, cmp conditionComparator) bool {
	matchesAny := func(a string) bool {
		for _, e := range expected {
			if cmp(e, a) {
				return true
			}
		}
		return false
	}

	useForAll := qualifier == qualifierForAllValues || (qualifier == qualifierNone && negate)
	if useForAll {
		for _, a := range actual {
			if ok := matchesAny(a); ok == negate {
				return false
			}
		}
		return true // vacuously true over an empty/absent actual
	}
	for _, a := range actual {
		if ok := matchesAny(a); ok != negate {
			return true
		}
	}
	return false // vacuously false over an empty/absent actual
}