package contract

import (
	"bytes"
	"encoding/json"
	"errors"
	"fmt"
	"time"
	"unicode/utf8"

	"git.ipao.vip/rogee/go-sip/contracts"
	"github.com/santhosh-tekuri/jsonschema/v6"
)

type CommandEnvelope struct {
	SchemaVersion string          `json:"schema_version"`
	CommandType   string          `json:"command_type"`
	CommandID     string          `json:"command_id"`
	TenantID      string          `json:"tenant_id"`
	TenantKey     string          `json:"tenant_key"`
	TraceID       string          `json:"trace_id"`
	IssuedAt      string          `json:"issued_at"`
	NotAfter      string          `json:"not_after"`
	Payload       json.RawMessage `json:"payload"`
}

type ExecutePayload struct {
	ExecutionID       string         `json:"execution_id"`
	TaskID            string         `json:"task_id"`
	TaskItemID        string         `json:"task_item_id"`
	TaskRevision      int64          `json:"task_revision"`
	Callee            string         `json:"callee"`
	RoutePolicyID     string         `json:"route_policy_id"`
	CallerProfileID   string         `json:"caller_profile_id"`
	AgentVersionID    string         `json:"agent_version_id"`
	Variables         map[string]any `json:"variables"`
	RingTimeoutMS     int64          `json:"ring_timeout_ms"`
	MaxCallDurationMS int64          `json:"max_call_duration_ms"`
}

type EventEnvelope struct {
	SchemaVersion    string         `json:"schema_version"`
	EventID          string         `json:"event_id"`
	EventType        string         `json:"event_type"`
	TenantID         string         `json:"tenant_id"`
	TenantKey        string         `json:"tenant_key"`
	TraceID          string         `json:"trace_id"`
	OccurredAt       string         `json:"occurred_at"`
	AggregateType    string         `json:"aggregate_type"`
	AggregateID      string         `json:"aggregate_id"`
	AggregateVersion int64          `json:"aggregate_version"`
	Payload          map[string]any `json:"payload"`
}

var ErrInvalidTenantKey = errors.New("invalid tenant_key")

// ValidateJSON applies the imported JSON Schema. It intentionally validates
// the source contract instead of maintaining a second hand-written schema.
func ValidateJSON(raw []byte) error {
	return ValidateSourceSchema("mq.schema.json", raw)
}

// ValidateEvent applies the event-specific payload contract in addition to the
// generic MQ envelope contract.
func ValidateEvent(raw []byte) error {
	return ValidateSourceSchema("event-payloads.schema.json", raw)
}

func ValidateSourceSchema(schemaName string, raw []byte) error {
	var value any
	if err := json.Unmarshal(raw, &value); err != nil {
		return fmt.Errorf("decode json: %w", err)
	}
	var schemaDoc any
	if err := contracts.ReadJSON(schemaName, &schemaDoc); err != nil {
		return err
	}
	resource := "https://agent-call.invalid/contracts/" + schemaName
	compiler := jsonschema.NewCompiler()
	if err := compiler.AddResource(resource, schemaDoc); err != nil {
		return fmt.Errorf("register %s: %w", schemaName, err)
	}
	schema, err := compiler.Compile(resource)
	if err != nil {
		return fmt.Errorf("compile %s: %w", schemaName, err)
	}
	if err := schema.Validate(value); err != nil {
		return fmt.Errorf("%s validation: %w", schemaName, err)
	}
	return nil
}

func DecodeExecute(raw []byte) (CommandEnvelope, ExecutePayload, error) {
	if err := ValidateJSON(raw); err != nil {
		return CommandEnvelope{}, ExecutePayload{}, err
	}
	var envelope CommandEnvelope
	if err := json.Unmarshal(raw, &envelope); err != nil {
		return CommandEnvelope{}, ExecutePayload{}, fmt.Errorf("decode command envelope: %w", err)
	}
	if envelope.CommandType != "call.execute" {
		return CommandEnvelope{}, ExecutePayload{}, fmt.Errorf("unsupported command_type %q", envelope.CommandType)
	}
	if err := ValidateTenantKey(envelope.TenantKey); err != nil {
		return CommandEnvelope{}, ExecutePayload{}, err
	}
	var payload ExecutePayload
	if err := json.Unmarshal(envelope.Payload, &payload); err != nil {
		return CommandEnvelope{}, ExecutePayload{}, fmt.Errorf("decode call.execute payload: %w", err)
	}
	return envelope, payload, nil
}

func ValidateTenantKey(key string) error {
	if key == "" || !utf8.ValidString(key) {
		return fmt.Errorf("%w: must be non-empty valid UTF-8", ErrInvalidTenantKey)
	}
	if len([]byte(key)) > 224 {
		return fmt.Errorf("%w: %d UTF-8 bytes exceeds 224-byte routing budget", ErrInvalidTenantKey, len([]byte(key)))
	}
	return nil
}

func NotAfterExpired(raw string, now time.Time) (bool, error) {
	deadline, err := time.Parse(time.RFC3339Nano, raw)
	if err != nil {
		return false, fmt.Errorf("parse not_after: %w", err)
	}
	return !now.Before(deadline), nil
}

func CloneJSON(raw []byte) json.RawMessage {
	return bytes.Clone(raw)
}

type EventBuilder struct {
	TenantID    string
	TenantKey   string
	TraceID     string
	EventType   string
	Aggregate   string
	AggregateID string
	Version     int64
	Payload     map[string]any
}

func (b EventBuilder) Marshal(now time.Time, eventID string) ([]byte, error) {
	if err := ValidateTenantKey(b.TenantKey); err != nil {
		return nil, err
	}
	if b.Version < 1 {
		return nil, errors.New("aggregate version must be positive")
	}
	e := EventEnvelope{
		SchemaVersion: "1.0", EventID: eventID, EventType: b.EventType,
		TenantID: b.TenantID, TenantKey: b.TenantKey, TraceID: b.TraceID,
		OccurredAt: now.UTC().Format(time.RFC3339Nano), AggregateType: b.Aggregate,
		AggregateID: b.AggregateID, AggregateVersion: b.Version, Payload: b.Payload,
	}
	raw, err := json.Marshal(e)
	if err != nil {
		return nil, err
	}
	if err := ValidateJSON(raw); err != nil {
		return nil, err
	}
	if err := ValidateEvent(raw); err != nil {
		return nil, err
	}
	return raw, nil
}