package definition

import (
	"bytes"
	"crypto/sha256"
	"encoding/json"
	"fmt"
	"sort"
	"unicode/utf8"

	"git.yuntuo.hk/k2safe/orbit/internal/jsonvalue"
	"git.yuntuo.hk/k2safe/orbit/internal/jsonwire"
	core "git.yuntuo.hk/k2safe/orbit/model"
	"git.yuntuo.hk/k2safe/orbit/pulse/service"
)

const MaxSpecificationBytes = 256 << 10
const maxTimeoutMS = 30 * 86400000

type checker struct {
	result  Checked
	keys    map[string]bool
	queues  map[core.ID]bool
	timeout uint64
}
type scope map[string]Type

// Check 验证完整结构、词法数据依赖和资源边界；不修改调用方定义，也不访问数据库。
// 队列存在性、当前权限和不可变版本身份由发布事务另行核验。
func Check(in Specification) (Checked, error) {
	if in.SchemaVersion != 1 || in.TimeoutMS == 0 || in.TimeoutMS > maxTimeoutMS || (in.FailurePolicy != "REVIEW" && in.FailurePolicy != "FAIL_AFTER_SETTLED") {
		return Checked{}, invalid("specification", "schema_version=1, finite timeout and explicit failure policy required")
	}
	if err := checkType(in.InputType, 0); err != nil {
		return Checked{}, err
	}
	c := checker{keys: map[string]bool{}, queues: map[core.ID]bool{}, timeout: in.TimeoutMS}
	initial := scope{"input": in.InputType, "workflow": {Kind: "OBJECT", Fields: map[string]Type{"id": {Kind: "STRING"}, "business_key": {Kind: "STRING"}}}}
	width, err := c.block(in.Body, initial, 0)
	if err != nil {
		return Checked{}, err
	}
	if width > 32 || c.result.MaxTaskAttempts > 10000 {
		return Checked{}, invalid("specification", "parallel or total attempt budget exceeded")
	}
	raw, err := jsonwire.Marshal(in)
	if err != nil || len(raw) > MaxSpecificationBytes {
		return Checked{}, invalid("specification", "encoded definition exceeds 256 KiB or is invalid")
	}
	canonical, err := jsonvalue.Canonical(raw)
	if err != nil {
		return Checked{}, invalid("specification", "definition JSON exceeds supported depth or value limits")
	}
	c.result.Digest = core.Digest(sha256.Sum256(append([]byte("orbit.weave.spec.v1\x00"), canonical...)))
	c.result.MaxConcurrency = width
	for q := range c.queues {
		c.result.Queues = append(c.result.Queues, q)
	}
	sort.Slice(c.result.Queues, func(i, j int) bool { return c.result.Queues[i] < c.result.Queues[j] })
	return c.result, nil
}

func invalid(where, message string) error { return fmt.Errorf("%s: %s", where, message) }
func name(s string, limit int) bool {
	if len(s) == 0 || len(s) > limit {
		return false
	}
	for i, r := range s {
		if !(r >= 'a' && r <= 'z' || r >= 'A' && r <= 'Z' || r >= '0' && r <= '9' || i > 0 && (r == '_' || r == '.' || r == '-')) {
			return false
		}
	}
	return true
}
func cloneScope(in scope) scope {
	out := make(scope, len(in)+8)
	for key, value := range in {
		out[key] = value
	}
	return out
}
func (c *checker) block(b Block, parent scope, depth int) (uint32, error) {
	if depth > 4 || len(b.Steps) > 128 {
		return 0, invalid("body", "block depth or step limit exceeded")
	}
	if err := checkType(b.OutputType, 0); err != nil {
		return 0, err
	}
	env := cloneScope(parent)
	var width uint32
	for _, step := range b.Steps {
		if !name(step.Key, 64) || step.Key == "input" || step.Key == "workflow" || c.keys[step.Key] {
			return 0, invalid("step", "key must be unique and nonreserved")
		}
		c.keys[step.Key] = true
		c.result.Steps++
		if c.result.Steps > 128 {
			return 0, invalid("body", "at most 128 static steps allowed")
		}
		result, concurrency, err := c.step(step, env, depth)
		if err != nil {
			return 0, invalid(step.Key, err.Error())
		}
		env[step.Key] = result
		if concurrency > width {
			width = concurrency
		}
	}
	if err := checkValue(b.Output, b.OutputType, env, 0); err != nil {
		return 0, invalid("output", err.Error())
	}
	return width, nil
}
func (c *checker) step(s Step, env scope, depth int) (Type, uint32, error) {
	n := 0
	for _, present := range []bool{s.Task != nil, s.Branch != nil, s.Parallel != nil, s.Signal != nil, s.Timer != nil, s.Poll != nil} {
		if present {
			n++
		}
	}
	if n != 1 {
		return Type{}, 0, invalid("step", "exactly one kind configuration required")
	}
	switch s.Kind {
	case "TASK":
		if s.Task != nil {
			if err := c.task(*s.Task, env); err != nil {
				return Type{}, 0, err
			}
			c.result.MaxTaskAttempts += s.Task.Retry.MaxAttempts
			return s.Task.ResultType, 1, nil
		}
	case "SIGNAL":
		if s.Signal != nil {
			return s.Signal.PayloadType, 0, c.signal(*s.Signal, env)
		}
	case "TIMER":
		if s.Timer != nil && s.Timer.DelayMS > 0 && s.Timer.DelayMS <= c.timeout {
			return Type{Kind: "NULL"}, 0, nil
		}
	case "BRANCH":
		if s.Branch != nil {
			b := s.Branch
			if b.Default == nil || len(b.Cases) < 1 || len(b.Cases) > 16 {
				return Type{}, 0, invalid("branch", "1 to 16 cases and explicit default required")
			}
			width, err := c.block(*b.Default, env, depth+1)
			if err != nil {
				return Type{}, 0, err
			}
			for _, path := range b.Cases {
				if err := checkPredicate(path.When, env, 0); err != nil {
					return Type{}, 0, err
				}
				w, err := c.block(path.Body, env, depth+1)
				if err != nil {
					return Type{}, 0, err
				}
				if !sameType(path.Body.OutputType, b.Default.OutputType) {
					return Type{}, 0, invalid("branch", "all path output types must match")
				}
				if w > width {
					width = w
				}
			}
			return b.Default.OutputType, width, nil
		}
	case "PARALLEL":
		if s.Parallel != nil {
			if len(s.Parallel.Branches) < 2 || len(s.Parallel.Branches) > 8 {
				return Type{}, 0, invalid("parallel", "2 to 8 named branches required")
			}
			result := Type{Kind: "OBJECT", Fields: map[string]Type{}}
			var width uint32
			for _, branch := range s.Parallel.Branches {
				if !name(branch.Name, 64) {
					return Type{}, 0, invalid("parallel", "invalid branch name")
				}
				if _, exists := result.Fields[branch.Name]; exists {
					return Type{}, 0, invalid("parallel", "duplicate branch name")
				}
				w, err := c.block(branch.Body, env, depth+1)
				if err != nil {
					return Type{}, 0, err
				}
				width += w
				result.Fields[branch.Name] = branch.Body.OutputType
			}
			if width > 32 {
				return Type{}, 0, invalid("parallel", "at most 32 concurrent business tasks allowed")
			}
			return result, width, nil
		}
	case "POLL":
		if s.Poll != nil {
			p := s.Poll
			if p.MaxRounds == 0 || p.MaxRounds > 1000 || p.TimeoutMS == 0 || p.TimeoutMS > c.timeout || p.IntervalMS < 1000 || p.IntervalMS >= p.TimeoutMS || p.Task.TimeoutMS > p.TimeoutMS {
				return Type{}, 0, invalid("poll", "finite rounds, interval and compatible time budgets required")
			}
			if err := c.task(p.Task, env); err != nil {
				return Type{}, 0, err
			}
			status, err := pathType(p.Task.ResultType, p.StatusPath)
			if err != nil || status.Kind != "STRING" || len(status.Enum) == 0 || len(p.Pending) == 0 || len(p.Succeeded) == 0 {
				return Type{}, 0, invalid("poll", "status must be a declared string enum with pending and success cases")
			}
			seen := map[string]bool{}
			for _, group := range [][]string{p.Pending, p.Succeeded, p.Failed, p.Review} {
				for _, v := range group {
					if !contains(status.Enum, v) || seen[v] {
						return Type{}, 0, invalid("poll", "status groups must form an exact disjoint partition")
					}
					seen[v] = true
				}
			}
			if len(seen) != len(status.Enum) {
				return Type{}, 0, invalid("poll", "unmapped status enum value")
			}
			if p.FinalSignal != nil {
				if err := c.signal(*p.FinalSignal, env); err != nil {
					return Type{}, 0, err
				}
				if p.FinalSignal.TimeoutMS != p.TimeoutMS || !sameType(p.FinalSignal.PayloadType, p.Task.ResultType) {
					return Type{}, 0, invalid("poll", "final signal must share result type and poll deadline")
				}
			}
			c.result.MaxTaskAttempts += p.MaxRounds * p.Task.Retry.MaxAttempts
			return p.Task.ResultType, 1, nil
		}
	}
	return Type{}, 0, invalid("step", "unknown kind, mismatched configuration or invalid timer")
}

func (c *checker) task(t Task, env scope) error {
	if t.TimeoutMS == 0 || t.TimeoutMS > c.timeout || t.InputType.Kind == "NULL" || t.ResultType.Kind == "NULL" {
		return invalid("task", "finite timeout and non-null payload/result types required")
	}
	// 复用Pulse的处理器/策略边界，但定义必须显式提供生效值，不能在后续发布时解释不同默认值。
	v, err := service.NormalizeSubmit(service.SubmitInput{QueueID: t.QueueID, Handler: t.Handler, HandlerVersion: t.HandlerVersion, PayloadVersion: t.PayloadVersion, Payload: json.RawMessage(`{}`), TaskTimeoutMS: t.TimeoutMS, RecoverySafety: t.RecoverySafety, Retry: t.Retry, Priority: t.Priority})
	if err != nil || v.Retry != t.Retry || v.RecoverySafety != t.RecoverySafety {
		return invalid("task", "invalid or incomplete frozen Pulse policy")
	}
	if err := checkType(t.InputType, 0); err != nil {
		return err
	}
	if err := checkType(t.ResultType, 0); err != nil {
		return err
	}
	if err := checkValue(t.Input, t.InputType, env, 0); err != nil {
		return err
	}
	if t.Input.Kind == "LITERAL" && bytes.Equal(bytes.TrimSpace(t.Input.Literal), []byte("null")) {
		return invalid("task", "null task input is not accepted by Pulse")
	}
	for _, key := range []*Value{t.BusinessKey, t.ConcurrencyKey} {
		if key != nil {
			if err := checkValue(*key, Type{Kind: "STRING"}, env, 0); err != nil {
				return err
			}
		}
	}
	c.queues[t.QueueID] = true
	return nil
}
func (c *checker) signal(s Signal, env scope) error {
	if !name(s.Name, 128) || !name(s.PayloadVersion, 32) || s.TimeoutMS == 0 || s.TimeoutMS > c.timeout {
		return invalid("signal", "name, payload version and finite timeout required")
	}
	if err := checkType(s.PayloadType, 0); err != nil {
		return err
	}
	if err := checkValue(s.Correlation, Type{Kind: "STRING"}, env, 0); err != nil {
		return err
	}
	if s.Correlation.Kind == "LITERAL" {
		var value string
		if json.Unmarshal(s.Correlation.Literal, &value) != nil || len(value) == 0 || len(value) > 512 {
			return invalid("signal", "literal correlation must be a nonempty string up to 512 bytes")
		}
	}
	return nil
}

func checkType(t Type, depth int) error {
	if depth > 8 || len(t.Fields) > 64 || len(t.Enum) > 32 {
		return invalid("type", "schema depth or width limit exceeded")
	}
	if t.Kind != "OBJECT" && len(t.Fields) != 0 || t.Kind != "ARRAY" && t.Items != nil || t.Kind != "STRING" && len(t.Enum) != 0 {
		return invalid("type", "fields, items or enum do not match kind")
	}
	switch t.Kind {
	case "JSON", "NUMBER", "BOOLEAN", "NULL":
	case "STRING":
		seen := map[string]bool{}
		for _, value := range t.Enum {
			if !utf8.ValidString(value) || len(value) > 128 || seen[value] {
				return invalid("type", "invalid or duplicate string enum value")
			}
			seen[value] = true
		}
	case "OBJECT":
		for key, field := range t.Fields {
			if !name(key, 64) {
				return invalid("type", "invalid object field name")
			}
			if err := checkType(field, depth+1); err != nil {
				return err
			}
		}
	case "ARRAY":
		if t.Items == nil {
			return invalid("type", "array items type required")
		}
		return checkType(*t.Items, depth+1)
	default:
		return invalid("type", "unknown kind")
	}
	return nil
}
func sameType(a, b Type) bool { return assignable(a, b) && assignable(b, a) }
func assignable(actual, expected Type) bool {
	if expected.Kind == "JSON" {
		return true
	}
	if actual.Kind != expected.Kind {
		return false
	}
	switch expected.Kind {
	case "OBJECT":
		if len(actual.Fields) != len(expected.Fields) {
			return false
		}
		for key, t := range expected.Fields {
			v, ok := actual.Fields[key]
			if !ok || !assignable(v, t) {
				return false
			}
		}
	case "ARRAY":
		return actual.Items != nil && expected.Items != nil && assignable(*actual.Items, *expected.Items)
	case "STRING":
		if len(expected.Enum) == 0 {
			return true
		}
		if len(actual.Enum) == 0 {
			return false
		}
		for _, v := range actual.Enum {
			if !contains(expected.Enum, v) {
				return false
			}
		}
	}
	return true
}
func contains(values []string, value string) bool {
	for _, v := range values {
		if v == value {
			return true
		}
	}
	return false
}
func pathType(t Type, path []string) (Type, error) {
	if len(path) > 8 {
		return Type{}, invalid("reference", "path exceeds 8 fields")
	}
	for _, key := range path {
		if t.Kind != "OBJECT" {
			return Type{}, invalid("reference", "path crosses a non-object or untyped JSON value")
		}
		var ok bool
		t, ok = t.Fields[key]
		if !ok {
			return Type{}, invalid("reference", "field not declared")
		}
	}
	return t, nil
}
func referenceType(r Reference, env scope) (Type, error) {
	t, ok := env[r.Source]
	if !ok {
		return Type{}, invalid("reference", "source is missing, forward, conditional or outside this block")
	}
	return pathType(t, r.Path)
}

func checkValue(v Value, expected Type, env scope, depth int) error {
	if depth > 8 {
		return invalid("value", "expression depth exceeds 8")
	}
	if v.Kind != "LITERAL" && len(v.Literal) != 0 || v.Kind != "REFERENCE" && v.Reference != nil || v.Kind != "OBJECT" && len(v.Fields) != 0 || v.Kind != "ARRAY" && len(v.Items) != 0 {
		return invalid("value", "configuration does not match kind")
	}
	switch v.Kind {
	case "LITERAL":
		return ValidateData(expected, v.Literal)
	case "REFERENCE":
		if v.Reference == nil {
			return invalid("reference", "source required")
		}
		actual, err := referenceType(*v.Reference, env)
		if err != nil {
			return err
		}
		if !assignable(actual, expected) {
			return invalid("reference", "source and target types are incompatible")
		}
	case "OBJECT":
		if expected.Kind != "OBJECT" && expected.Kind != "JSON" || len(v.Fields) > 64 {
			return invalid("value", "object expression has incompatible type or too many fields")
		}
		if expected.Kind == "OBJECT" && len(v.Fields) != len(expected.Fields) {
			return invalid("value", "object expression must define every field exactly")
		}
		for key, child := range v.Fields {
			if !name(key, 64) {
				return invalid("value", "invalid object field")
			}
			t := Type{Kind: "JSON"}
			if expected.Kind == "OBJECT" {
				var ok bool
				t, ok = expected.Fields[key]
				if !ok {
					return invalid("value", "extra object field")
				}
			}
			if err := checkValue(child, t, env, depth+1); err != nil {
				return err
			}
		}
	case "ARRAY":
		if expected.Kind != "ARRAY" && expected.Kind != "JSON" || len(v.Items) > 256 {
			return invalid("value", "array expression has incompatible type or too many elements")
		}
		t := Type{Kind: "JSON"}
		if expected.Kind == "ARRAY" {
			t = *expected.Items
		}
		for _, child := range v.Items {
			if err := checkValue(child, t, env, depth+1); err != nil {
				return err
			}
		}
	default:
		return invalid("value", "unknown kind")
	}
	return nil
}

func scalarType(v Value, env scope) (string, error) {
	if err := checkValue(v, Type{Kind: "JSON"}, env, 0); err != nil {
		return "", err
	}
	var kind string
	switch v.Kind {
	case "REFERENCE":
		t, err := referenceType(*v.Reference, env)
		if err != nil {
			return "", err
		}
		kind = t.Kind
	case "LITERAL":
		var raw any
		d := json.NewDecoder(bytes.NewReader(v.Literal))
		d.UseNumber()
		if err := d.Decode(&raw); err != nil {
			return "", err
		}
		switch raw.(type) {
		case nil:
			kind = "NULL"
		case string:
			kind = "STRING"
		case bool:
			kind = "BOOLEAN"
		case json.Number:
			kind = "NUMBER"
		}
	}
	if kind != "STRING" && kind != "NUMBER" && kind != "BOOLEAN" && kind != "NULL" {
		return "", invalid("predicate", "only typed scalar comparisons allowed")
	}
	return kind, nil
}
func checkPredicate(p Predicate, env scope, depth int) error {
	if depth > 8 {
		return invalid("predicate", "expression depth exceeds 8")
	}
	switch p.Op {
	case "AND", "OR", "NOT":
		if p.Left != nil || p.Right != nil || len(p.Arguments) > 16 || (p.Op == "NOT" && len(p.Arguments) != 1) || (p.Op != "NOT" && len(p.Arguments) < 2) {
			return invalid("predicate", "invalid logical arguments")
		}
		for _, child := range p.Arguments {
			if err := checkPredicate(child, env, depth+1); err != nil {
				return err
			}
		}
	case "EQ", "NE", "LT", "LE", "GT", "GE":
		if p.Left == nil || p.Right == nil || len(p.Arguments) != 0 {
			return invalid("predicate", "exactly two comparison operands required")
		}
		left, err := scalarType(*p.Left, env)
		if err != nil {
			return err
		}
		right, err := scalarType(*p.Right, env)
		if err != nil {
			return err
		}
		if left != right || (p.Op != "EQ" && p.Op != "NE" && left != "STRING" && left != "NUMBER") {
			return invalid("predicate", "incompatible comparison operands")
		}
	default:
		return invalid("predicate", "unknown operator")
	}
	return nil
}