// session_service.go 实现 SessionService 接口。Create 走完整事务（worktree
// acquire + supervisor.Spawn）的实现见 F3；本文件仅放骨架 + ResolveBranch
// pure helper。
package acp

import (
	"context"
	"fmt"
	"strings"

	"github.com/google/uuid"

	"github.com/yan1h/agent-coding-workflow/internal/audit"
	"github.com/yan1h/agent-coding-workflow/internal/infra/errs"
	"github.com/yan1h/agent-coding-workflow/internal/project"
	"github.com/yan1h/agent-coding-workflow/internal/workspace"
)

// SessionServiceConfig 是 service 的限流配置（从 AcpConfig 派生）。
type SessionServiceConfig struct {
	MaxActiveGlobal  int
	MaxActivePerUser int
}

// ProjectAccess 是 acp 模块对 project 模块的窄接口；adapter 在 app.go 实现。
type ProjectAccess interface {
	GetProjectByWorkspace(ctx context.Context, wsID uuid.UUID) (*project.Project, error)
	GetIssueByNumber(ctx context.Context, projectID uuid.UUID, number int) (*project.Issue, error)
	GetRequirementByNumber(ctx context.Context, projectID uuid.UUID, number int) (*project.Requirement, error)
}

type sessionService struct {
	repo   Repository
	wsSvc  workspace.WorkspaceService
	wtSvc  workspace.WorktreeService
	wsRepo workspace.Repository
	pa     ProjectAccess
	sup    *Supervisor
	audit  audit.Recorder
	cfg    SessionServiceConfig
}

// NewSessionService 构造 SessionService。
func NewSessionService(repo Repository, wsSvc workspace.WorkspaceService,
	wtSvc workspace.WorktreeService, wsRepo workspace.Repository,
	pa ProjectAccess, sup *Supervisor, rec audit.Recorder,
	cfg SessionServiceConfig) SessionService {
	return &sessionService{
		repo: repo, wsSvc: wsSvc, wtSvc: wtSvc, wsRepo: wsRepo,
		pa: pa, sup: sup, audit: rec, cfg: cfg,
	}
}

// ResolveBranch 是 spec §8.1 的纯函数实现：根据 CreateSessionInput 决定
// (branch, isMainWorktree)。允许独立单测，不依赖 service 状态。
//
// 规则（按优先级）：
//  1. in.Branch 显式：直接用；isMain = (== ws.DefaultBranch)
//  2. in.IssueNumber：拉 issue，校验 workspace 关联，命名 "issue/<slug>-<num>"
//  3. in.RequirementNumber：拉 requirement，校验 workspace，命名 "req/<slug>-<num>"
//  4. 都没给：fallback "acp-auto/<8-hex>"，isMain = false
func ResolveBranch(ctx context.Context, ws *workspace.Workspace, sessionID uuid.UUID,
	in CreateSessionInput, projectSlug string, pa ProjectAccess) (string, bool, error) {

	if in.Branch != nil && *in.Branch != "" {
		br := *in.Branch
		return br, br == ws.DefaultBranch, nil
	}

	if in.IssueNumber != nil {
		iss, err := pa.GetIssueByNumber(ctx, ws.ProjectID, *in.IssueNumber)
		if err != nil {
			return "", false, err
		}
		if iss.WorkspaceID != nil && *iss.WorkspaceID != ws.ID {
			return "", false, errs.New(errs.CodeInvalidInput,
				fmt.Sprintf("issue #%d already linked to other workspace", *in.IssueNumber))
		}
		return fmt.Sprintf("issue/%s-%d", projectSlug, iss.Number), false, nil
	}

	if in.RequirementNumber != nil {
		req, err := pa.GetRequirementByNumber(ctx, ws.ProjectID, *in.RequirementNumber)
		if err != nil {
			return "", false, err
		}
		if req.WorkspaceID != nil && *req.WorkspaceID != ws.ID {
			return "", false, errs.New(errs.CodeInvalidInput,
				fmt.Sprintf("requirement #%d already linked to other workspace", *in.RequirementNumber))
		}
		return fmt.Sprintf("req/%s-%d", projectSlug, req.Number), false, nil
	}

	short := strings.ReplaceAll(sessionID.String(), "-", "")
	if len(short) > 8 {
		short = short[:8]
	}
	return fmt.Sprintf("acp-auto/%s", short), false, nil
}

// Create / Get / List / Terminate 在 F3 实现；先放占位让接口断言通过。
func (s *sessionService) Create(ctx context.Context, c Caller, in CreateSessionInput) (*Session, error) {
	return nil, errs.New(errs.CodeInternal, "SessionService.Create not implemented (F3)")
}

func (s *sessionService) Get(ctx context.Context, c Caller, id uuid.UUID) (*Session, error) {
	return nil, errs.New(errs.CodeInternal, "SessionService.Get not implemented (F3)")
}

func (s *sessionService) List(ctx context.Context, c Caller, all bool) ([]*Session, error) {
	return nil, errs.New(errs.CodeInternal, "SessionService.List not implemented (F3)")
}

func (s *sessionService) Terminate(ctx context.Context, c Caller, id uuid.UUID) error {
	return errs.New(errs.CodeInternal, "SessionService.Terminate not implemented (F3)")
}