package agent

import (
	"context"
	"time"

	"chat-agent-system/internal/config"
)

type Request struct {
	WorkDir      string        `json:"work_dir"`
	Prompt       string        `json:"prompt"`
	Instructions string        `json:"instructions"`
	Targets      []string      `json:"targets"`
	Timeout      time.Duration `json:"timeout"`
	// ToolProfile is workspace (default, document tools) or reasoning (no tools).
	ToolProfile string `json:"tool_profile,omitempty"`
	// OnEvent 可选过程事件回调（nil = 调用方不需要过程，后端行为与现状完全一致）。
	// 实现方必须保证：回调在 Execute 返回前完成（同步调用或等待收尾），无泄漏 goroutine；
	// 回调内不得阻塞（消费方自行节流/异步入队）。
	OnEvent func(ev ProcessEvent)
}

// ProcessEvent 对 agentx 事件与远程 runner NDJSON 过程帧的统一投影，
// 供小队过程流式展示消费（见 .doc/system-design/2026-09-28-agent-process-streaming-and-subagent-view-design.md）。
type ProcessEvent struct {
	Type   string // text_delta | reasoning_delta | tool_call_delta | tool_execution_start | tool_execution_end | message_end | ...
	Text   string // delta 文本（Type 为 *_delta 时）
	Tool   string // 工具名（tool_* 时）
	Detail string // 工具参数/结果摘要（tool_execution_* 时）
}

const (
	ToolProfileWorkspace = "workspace"
	ToolProfileReasoning = "reasoning"
)

type Result struct {
	Success     bool              `json:"success"`
	Patches     map[string][]byte `json:"patches"`
	Logs        string            `json:"logs"`
	ErrorReason string            `json:"error_reason"`
	// Retryable marks a provider-transient failure that may receive a
	// fresh step invocation. Permanent missing deliverables stay false.
	Retryable bool `json:"retryable,omitempty"`
	// PromptTokens and CompletionTokens are set by pi-native when the provider reports usage.
	PromptTokens     int `json:"prompt_tokens,omitempty"`
	CompletionTokens int `json:"completion_tokens,omitempty"`
}

type Backend interface {
	Name() string
	Execute(ctx context.Context, req Request) (*Result, error)
}

func NewBackend(name string, cfg *config.Config) Backend {
	var inner Backend
	switch name {
	case "pi-agent":
		inner = &PiAgentBackend{cfg: cfg}
	case "pi-native":
		inner = &fallbackBackend{
			primary:  NewPiNativeBackend(cfg),
			fallback: &PiAgentBackend{cfg: cfg},
		}
	default:
		inner = &StubBackend{}
	}
	max := 8
	if cfg != nil && cfg.MaxConcurrentAgents > 0 {
		max = cfg.MaxConcurrentAgents
	}
	return WrapWithConcurrencyLimit(inner, max)
}