package orbit

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"io"
	"strconv"
	"strings"
)

type handlerCompletion struct {
	attemptID string
	result    WorkerFinish
}

func (w *Worker) invoke(ctx context.Context, handler WorkerHandler, execution WorkerExecution, ref WorkerAttempt, results chan<- handlerCompletion, runDone <-chan struct{}) {
	out := WorkerFinish{Ref: ref, Outcome: WorkerUnknown, ErrorCode: "HANDLER_ABORTED", Result: json.RawMessage(`{}`)}
	completed := false
	defer func() {
		if recover() != nil {
			out = unknownHandlerResult(ref, "HANDLER_PANIC")
		} else if !completed {
			out = unknownHandlerResult(ref, "HANDLER_ABORTED")
		}
		w.running.Add(-1)
		select {
		case results <- handlerCompletion{attemptID: ref.AttemptID, result: out}:
		case <-runDone:
		}
	}()
	if ctx.Err() != nil {
		out = unknownHandlerResult(ref, "LEASE_LOST")
		if errors.Is(context.Cause(ctx), ErrTaskCancellationRequested) {
			out = cancelledHandlerResult(ref, nil)
		}
		completed = true
		return
	}
	w.started.Add(1)
	result, err := handler.Handle(ctx, execution)
	if err == nil {
		result = append(json.RawMessage(nil), result...)
		if validHandlerResult(result) {
			out = WorkerFinish{Ref: ref, Outcome: WorkerSucceeded, Result: result}
		} else {
			out = unknownHandlerResult(ref, "INVALID_HANDLER_RESULT")
		}
	} else {
		var known *WorkerFailure
		var cancelled *WorkerCancellationConfirmed
		if errors.As(err, &cancelled) && cancelled != nil && errors.Is(context.Cause(ctx), ErrTaskCancellationRequested) {
			out = cancelledHandlerResult(ref, cancelled.Details)
		} else if errors.As(err, &known) && known != nil && workerName(known.Code, 64) {
			details := append(json.RawMessage(nil), known.Details...)
			if len(details) == 0 {
				details = json.RawMessage(`{}`)
			}
			if validHandlerResult(details) {
				out = WorkerFinish{Ref: ref, Outcome: WorkerFailed, ErrorCode: known.Code, Result: details, Retryable: known.Retryable}
			} else {
				out = unknownHandlerResult(ref, "INVALID_HANDLER_RESULT")
			}
		} else if errors.Is(context.Cause(ctx), ErrExecutionLeaseLost) {
			out = unknownHandlerResult(ref, "LEASE_LOST")
		} else {
			out = unknownHandlerResult(ref, "HANDLER_ERROR")
		}
	}
	completed = true
}

func cancelledHandlerResult(ref WorkerAttempt, details json.RawMessage) WorkerFinish {
	details = append(json.RawMessage(nil), details...)
	if len(details) == 0 {
		details = json.RawMessage(`{}`)
	}
	if !validHandlerResult(details) {
		return unknownHandlerResult(ref, "INVALID_HANDLER_RESULT")
	}
	return WorkerFinish{Ref: ref, Outcome: WorkerCancelled, ErrorCode: "CANCEL_CONFIRMED", Result: details}
}
func unknownHandlerResult(ref WorkerAttempt, code string) WorkerFinish {
	return WorkerFinish{Ref: ref, Outcome: WorkerUnknown, ErrorCode: code, Result: json.RawMessage(`{}`)}
}

// validHandlerResult 提前拒绝服务端无法持久化的结果，避免失效报告无限重报。
// 只检验数值范围；不把精确业务数字改写成 float64。
func validHandlerResult(raw json.RawMessage) bool {
	if len(raw) == 0 || len(raw) > 256<<10 || bytes.Equal(bytes.TrimSpace(raw), []byte("null")) {
		return false
	}
	// 预留 task.finish 的信封/body 嵌套，避免合法结果单独校验后在帧校验阶段超深。
	frame := append([]byte(`{"body":{"result":`), raw...)
	frame = append(frame, []byte(`}}`)...)
	if validateWorkerJSON(frame) != nil {
		return false
	}
	d := json.NewDecoder(bytes.NewReader(raw))
	d.UseNumber()
	for {
		value, err := d.Token()
		if err == io.EOF {
			return true
		}
		if err != nil {
			return false
		}
		number, ok := value.(json.Number)
		if !ok {
			continue
		}
		s := string(number)
		if len(s) > 256 {
			return false
		}
		if _, err := strconv.ParseFloat(s, 64); err != nil {
			return false
		}
		s = strings.TrimPrefix(s, "-")
		exponent := 0
		if i := strings.IndexAny(s, "eE"); i >= 0 {
			var err error
			exponent, err = strconv.Atoi(s[i+1:])
			if err != nil || exponent < -308 || exponent > 308 {
				return false
			}
			s = s[:i]
		}
		if i := strings.IndexByte(s, '.'); i >= 0 {
			exponent -= len(s) - i - 1
			s = s[:i] + s[i+1:]
		}
		s = strings.TrimLeft(s, "0")
		if s == "" {
			continue
		}
		for strings.HasSuffix(s, "0") {
			s = s[:len(s)-1]
			exponent++
		}
		if exponent < -308 || exponent > 308 || exponent+len(s)-1 > 308 {
			return false
		}
	}
}