package native

import (
	"context"
	"errors"
	"strings"

	"agent-native/exec"
)

// contractBackend 把 Backend 适配为 exec.ContractBackend。
// 独立类型的原因：旧门面 Execute(ctx, exec.Request) 与契约的
// Execute(ctx, exec.ContractRequest) 签名冲突，同名方法不能并存；
// 包装让现有 squad 消费（旧门面）与契约消费（conformance/Core）互不影响。
type contractBackend struct{ b *Backend }

// Contract 返回该后端的契约形态（N1 WP6；旧门面保持不变）。
func (b *Backend) Contract() exec.ContractBackend {
	return contractBackend{b: b}
}

func (c contractBackend) Descriptor() exec.BackendDescriptor {
	return exec.BackendDescriptor{
		Name:         c.b.Name(),
		Capabilities: []exec.Capability{exec.CapText, exec.CapStream, exec.CapTools},
	}
}

func (c contractBackend) Execute(ctx context.Context, req exec.ContractRequest) (*exec.ContractResult, error) {
	var onEvent func(ev exec.ProcessEvent)
	if req.OnEvent != nil {
		next := req.OnEvent
		onEvent = func(ev exec.ProcessEvent) {
			next(exec.Event{Kind: exec.EventKind(ev.Type), Text: ev.Text, Tool: ev.Tool, Detail: ev.Detail})
		}
	}
	// 契约语义：空 ToolPolicy.Profile 等同 reasoning（无工具纯文本任务）。
	profile := strings.TrimSpace(req.ToolPolicy.Profile)
	if profile == "" {
		profile = exec.ToolProfileReasoning
	}
	old := exec.Request{
		Prompt:        req.Prompt,
		Instructions:  req.Instructions,
		ExecutionID:   req.ExecutionID,
		Targets:       append([]string(nil), req.Targets...),
		ToolProfile:   profile,
		ToolAllowlist: append([]string(nil), req.ToolPolicy.Allowlist...),
		WorkDir:       req.Workspace.Root,
		OnEvent:       onEvent,
	}
	if b := req.ContractBudget; b.MaxPromptTokens > 0 || b.MaxCompletionTokens > 0 || !b.Deadline.IsZero() {
		old.Budget = &exec.Budget{
			MaxPromptTokens:     b.MaxPromptTokens,
			MaxCompletionTokens: b.MaxCompletionTokens,
			Deadline:            b.Deadline,
		}
	}
	res, err := c.b.Execute(ctx, old)
	if err != nil {
		// 传输/实现级错误：按契约映射为 Unknown，不经 Go error 返回业务终态。
		return &exec.ContractResult{
			Outcome: exec.OutcomeUnknown,
			Err:     &exec.Error{Code: exec.ErrProviderUnavailable, Reason: err.Error(), SideEffects: exec.SideEffectPossible},
		}, nil
	}
	out := &exec.ContractResult{
		Logs: res.Logs,
		Usage: exec.Usage{
			PromptTokens:     res.PromptTokens,
			CompletionTokens: res.CompletionTokens,
		},
	}
	switch {
	case res.Success:
		out.Outcome = exec.OutcomeSucceeded
		out.Files = res.Patches
	case errors.Is(ctx.Err(), context.Canceled):
		out.Outcome = exec.OutcomeCanceled
		out.Err = &exec.Error{Code: exec.ErrCanceled, Reason: res.ErrorReason, SideEffects: exec.SideEffectPossible}
	case errors.Is(ctx.Err(), context.DeadlineExceeded):
		out.Outcome = exec.OutcomeFailed
		out.Err = &exec.Error{Code: exec.ErrDeadlineExceeded, Reason: res.ErrorReason, SideEffects: exec.SideEffectPossible}
	default:
		out.Outcome = exec.OutcomeFailed
		out.Err = &exec.Error{Code: exec.ErrProviderRejected, Reason: res.ErrorReason, Retryable: res.Retryable, SideEffects: exec.SideEffectPossible}
	}
	return out, nil
}