// Package project 内的 issue_service.go 实装 IssueService。
//
// 校验要点：
//   - requirement 必须与 issue 同 project（fakeRepo / sql 都按 project_id 索引，
//     此处的校验主要在 service 层把 RequirementNumber 解析为 RequirementID）。
//   - 已 closed requirement：拒绝挂新 issue；已挂载 issue 仍可改其它字段，
//     但不能从游离/别处移过来。
//   - 已归档 project：所有写操作拒绝。
package project

import (
	"context"

	"github.com/google/uuid"

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

type issueService struct {
	repo  Repository
	audit audit.Recorder
}

// NewIssueService 构造 IssueService。
func NewIssueService(repo Repository, rec audit.Recorder) IssueService {
	return &issueService{repo: repo, audit: rec}
}

// resolveRequirement 把 *number 解析为 *Requirement，并校验同 project + 未关闭。
// number == nil → 返回 (nil, nil) 表示不挂载。
func (s *issueService) resolveRequirement(ctx context.Context, p *Project, number *int) (*Requirement, error) {
	if number == nil {
		return nil, nil
	}
	r, err := s.repo.GetRequirementByNumber(ctx, p.ID, *number)
	if err != nil {
		return nil, err
	}
	if r.Status == StatusClosed {
		return nil, errs.New(errs.CodeRequirementClosed, "目标需求已关闭，无法挂载")
	}
	return r, nil
}

func (s *issueService) Create(ctx context.Context, c Caller, slug string, in CreateIssueInput) (*Issue, error) {
	if in.Title == "" {
		return nil, errs.New(errs.CodeInvalidInput, "title 必填")
	}
	p, err := loadProjectForWrite(ctx, s.repo, c, slug)
	if err != nil {
		return nil, err
	}
	r, err := s.resolveRequirement(ctx, p, in.RequirementNumber)
	if err != nil {
		return nil, err
	}
	var reqID *uuid.UUID
	if r != nil {
		reqID = &r.ID
	}
	in1 := &Issue{
		ID: uuid.New(), ProjectID: p.ID, RequirementID: reqID,
		Title: in.Title, Description: in.Description,
		AssigneeID: in.AssigneeID, CreatedBy: c.UserID,
	}
	out, err := s.createWithRetry(ctx, in1)
	if err != nil {
		return nil, err
	}
	meta := map[string]any{"project_id": p.ID.String(), "number": out.Number}
	if reqID != nil {
		meta["requirement_id"] = reqID.String()
	}
	s.recordAudit(ctx, c, "issue.create", out.ID.String(), meta)
	return out, nil
}

func (s *issueService) createWithRetry(ctx context.Context, in *Issue) (*Issue, error) {
	for attempt := 0; attempt < 2; attempt++ {
		out, err := s.repo.CreateIssue(ctx, in)
		if err == nil {
			return out, nil
		}
		if !IsUniqueViolation(err) {
			return nil, err
		}
	}
	return nil, errs.New(errs.CodeInternal, "issue number 持续冲突")
}

func (s *issueService) Get(ctx context.Context, c Caller, slug string, number int) (*Issue, error) {
	p, err := loadProjectForRead(ctx, s.repo, c, slug)
	if err != nil {
		return nil, err
	}
	return s.repo.GetIssueByNumber(ctx, p.ID, number)
}

func (s *issueService) List(ctx context.Context, c Caller, slug string, f IssueFilter) ([]*Issue, error) {
	p, err := loadProjectForRead(ctx, s.repo, c, slug)
	if err != nil {
		return nil, err
	}
	if f.Status != "" && f.Status != StatusOpen && f.Status != StatusClosed {
		return nil, errs.New(errs.CodeInvalidInput, "status 非法")
	}
	// f.Requirement 三态：nil / *==0 (none) / *>0 (number → id)
	var reqID *uuid.UUID
	if f.Requirement != nil && *f.Requirement > 0 {
		r, err := s.repo.GetRequirementByNumber(ctx, p.ID, *f.Requirement)
		if err != nil {
			return nil, err
		}
		reqID = &r.ID
	}
	return s.repo.ListIssues(ctx, p.ID, f, reqID)
}

func (s *issueService) Update(ctx context.Context, c Caller, slug string, number int, in UpdateIssueInput) (*Issue, error) {
	p, err := loadProjectForWrite(ctx, s.repo, c, slug)
	if err != nil {
		return nil, err
	}
	cur, err := s.repo.GetIssueByNumber(ctx, p.ID, number)
	if err != nil {
		return nil, err
	}

	title, desc := cur.Title, cur.Description
	if in.Title != nil {
		title = *in.Title
	}
	if in.Description != nil {
		desc = *in.Description
	}

	// requirement 三态：未传（in.RequirementNumber == nil）→ 保持
	//                 传 nil 指针（**nil）→ detach
	//                 传值（*RequirementNumber 不是 nil）→ resolve & validate
	reqID := cur.RequirementID
	auditFrom := ""
	auditTo := ""
	if in.RequirementNumber != nil {
		auditFrom = "<unchanged>"
		if cur.RequirementID != nil {
			auditFrom = cur.RequirementID.String()
		}
		if *in.RequirementNumber == nil {
			reqID = nil
			auditTo = "<none>"
		} else {
			r, err := s.resolveRequirement(ctx, p, *in.RequirementNumber)
			if err != nil {
				return nil, err
			}
			reqID = &r.ID
			auditTo = r.ID.String()
		}
	}

	out, err := s.repo.UpdateIssueCore(ctx, cur.ID, title, desc, reqID)
	if err != nil {
		return nil, err
	}
	meta := map[string]any{"changed_fields": "<various>"}
	if auditFrom != "" {
		meta["from_requirement"] = auditFrom
		meta["to_requirement"] = auditTo
	}
	s.recordAudit(ctx, c, "issue.update", out.ID.String(), meta)
	return out, nil
}

func (s *issueService) Assign(ctx context.Context, c Caller, slug string, number int, assignee *uuid.UUID) (*Issue, error) {
	p, err := loadProjectForWrite(ctx, s.repo, c, slug)
	if err != nil {
		return nil, err
	}
	cur, err := s.repo.GetIssueByNumber(ctx, p.ID, number)
	if err != nil {
		return nil, err
	}
	from := "<none>"
	if cur.AssigneeID != nil {
		from = cur.AssigneeID.String()
	}
	to := "<none>"
	if assignee != nil {
		to = assignee.String()
	}
	out, err := s.repo.UpdateIssueAssignee(ctx, cur.ID, assignee)
	if err != nil {
		return nil, err
	}
	s.recordAudit(ctx, c, "issue.assign", out.ID.String(), map[string]any{"from": from, "to": to})
	return out, nil
}

func (s *issueService) Close(ctx context.Context, c Caller, slug string, number int) error {
	p, err := loadProjectForWrite(ctx, s.repo, c, slug)
	if err != nil {
		return err
	}
	cur, err := s.repo.GetIssueByNumber(ctx, p.ID, number)
	if err != nil {
		return err
	}
	if cur.Status == StatusClosed {
		return nil
	}
	if err := s.repo.CloseIssue(ctx, cur.ID); err != nil {
		return err
	}
	s.recordAudit(ctx, c, "issue.close", cur.ID.String(), nil)
	return nil
}

func (s *issueService) Reopen(ctx context.Context, c Caller, slug string, number int) error {
	p, err := loadProjectForWrite(ctx, s.repo, c, slug)
	if err != nil {
		return err
	}
	cur, err := s.repo.GetIssueByNumber(ctx, p.ID, number)
	if err != nil {
		return err
	}
	if cur.Status == StatusOpen {
		return nil
	}
	if err := s.repo.ReopenIssue(ctx, cur.ID); err != nil {
		return err
	}
	s.recordAudit(ctx, c, "issue.reopen", cur.ID.String(), nil)
	return nil
}

func (s *issueService) recordAudit(ctx context.Context, c Caller, action, targetID string, meta map[string]any) {
	if s.audit == nil {
		return
	}
	uid := c.UserID
	_ = s.audit.Record(context.WithoutCancel(ctx), audit.Entry{
		UserID: &uid, Action: action, TargetType: "issue", TargetID: targetID, Metadata: meta,
	})
}