package main

// ai_tasks.go 一句话生成多条待办/工单：调用 AI 把自然语言拆解成结构化草稿，
// 前端预览确认后再逐条走 SaveTodo / SaveTicket 正常落库。

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"strings"
	"time"

	"view/service/ai"
)

// AITaskDraft 是 AI 生成的一条草稿（todo 与 ticket 共用，前端按 kind 取字段）。
type AITaskDraft struct {
	Kind        string `json:"kind"` // todo | ticket
	Title       string `json:"title"`
	Content     string `json:"content"`     // todo 备注
	Description string `json:"description"` // ticket 描述
	Type        string `json:"type"`        // ticket: feature | bug | task | improvement
	Priority    string `json:"priority"`    // low | medium | high
	StartAt     string `json:"startAt"`     // ticket: YYYY-MM-DD
	DueAt       string `json:"dueAt"`       // todo: YYYY-MM-DDTHH:MM；ticket: YYYY-MM-DD
}

// AIGenerateTasks 把一句话拆解成多条待办或工单草稿（不落库，由前端确认后保存）。
func (a *App) AIGenerateTasks(kind, text string) ([]AITaskDraft, error) {
	if e := a.ready(); e != nil {
		return nil, e
	}
	if kind != "todo" && kind != "ticket" {
		return nil, errors.New("BAD_REQUEST")
	}
	text = strings.TrimSpace(text)
	if text == "" {
		return nil, errors.New("AI_EMPTY_MESSAGE")
	}
	provider, e := a.aiProvider()
	if e != nil {
		return nil, e
	}
	if e := a.checkAIPolicy(); e != nil {
		return nil, e
	}
	msgs := []ai.Message{
		{Role: "system", Content: aiTaskPrompt(kind)},
		{Role: "user", Content: text},
	}
	ctx, cancel := context.WithTimeout(a.ctx, 2*time.Minute)
	defer cancel()
	stream, e := provider.ChatStream(ctx, msgs)
	if e != nil {
		a.store.Log("error", "AI", "AI 任务生成请求失败", e.Error())
		return nil, e
	}
	var sb strings.Builder
	var usage *ai.Usage
	for chunk := range stream {
		if chunk.Usage != nil {
			usage = chunk.Usage
		}
		if chunk.Err != nil {
			a.store.Log("error", "AI", "AI 任务生成失败", chunk.Err.Error())
			return nil, chunk.Err
		}
		sb.WriteString(chunk.Content)
	}
	if usage != nil {
		go a.reportAIUsage(provider.Name(), usage.PromptTokens, usage.CompletionTokens, usage.Estimated)
	}
	drafts, pe := parseAITaskDrafts(kind, sb.String())
	if pe != nil {
		a.store.Log("warning", "AI", "AI 任务生成解析失败", sb.String())
		return nil, pe
	}
	a.store.Log("info", "AI", "AI 任务生成完成", fmt.Sprintf("kind=%s count=%d", kind, len(drafts)))
	return drafts, nil
}

func aiTaskPrompt(kind string) string {
	now := time.Now()
	weekdays := []string{"日", "一", "二", "三", "四", "五", "六"}
	head := fmt.Sprintf("今天是 %s（星期%s），当前时间 %s。\n", now.Format("2006-01-02"), weekdays[int(now.Weekday())], now.Format("15:04"))
	if kind == "ticket" {
		return head + `你是研发工单拆解助手。把用户的一句话拆成 1~10 条工单。
只输出 JSON 数组，禁止任何解释、markdown 围栏或多余文字。每个元素：
{"title":"简短标题(<=40字)","description":"补充细节，可为空","type":"feature|bug|task|improvement","priority":"low|medium|high","startAt":"YYYY-MM-DD","dueAt":"YYYY-MM-DD"}
规则：标题用与用户输入相同的语言；startAt 默认今天；dueAt 不得早于 startAt，用户未提及工期时按任务量合理估算（1~7 天）；能从用户话中推断出的日期（如“周五前”“下周”）必须转换为具体日期。`
	}
	return head + `你是待办事项拆解助手。把用户的一句话拆成 1~10 条待办。
只输出 JSON 数组，禁止任何解释、markdown 围栏或多余文字。每个元素：
{"title":"简短标题(<=40字)","content":"补充细节，可为空","priority":"low|medium|high","dueAt":"YYYY-MM-DDTHH:MM 或空字符串"}
规则：标题用与用户输入相同的语言；只有用户明确或可合理推断截止时间时才填 dueAt（如“明天下午”→ 明天 18:00），否则留空字符串。`
}

// parseAITaskDrafts 从模型输出中提取 JSON 数组并规范化字段。
func parseAITaskDrafts(kind, raw string) ([]AITaskDraft, error) {
	raw = stripFence(strings.TrimSpace(raw))
	start, end := strings.Index(raw, "["), strings.LastIndex(raw, "]")
	if start < 0 || end <= start {
		return nil, errors.New("AI_BAD_RESPONSE")
	}
	var list []AITaskDraft
	if json.Unmarshal([]byte(raw[start:end+1]), &list) != nil {
		return nil, errors.New("AI_BAD_RESPONSE")
	}
	today := time.Now().Format("2006-01-02")
	out := make([]AITaskDraft, 0, len(list))
	for _, d := range list {
		d.Kind = kind
		d.Title = strings.TrimSpace(d.Title)
		if d.Title == "" {
			continue
		}
		if r := []rune(d.Title); len(r) > 120 {
			d.Title = string(r[:120])
		}
		if d.Priority != "low" && d.Priority != "medium" && d.Priority != "high" {
			d.Priority = "medium"
		}
		if kind == "ticket" {
			switch d.Type {
			case "feature", "bug", "task", "improvement":
			default:
				d.Type = "task"
			}
			d.Content = ""
			if !validDateStr(d.StartAt) {
				d.StartAt = today
			}
			if !validDateStr(d.DueAt) {
				d.DueAt = time.Now().AddDate(0, 0, 3).Format("2006-01-02")
			}
			if d.DueAt < d.StartAt {
				d.DueAt = d.StartAt
			}
		} else {
			d.Type, d.Description, d.StartAt = "", "", ""
			d.DueAt = normalizeTodoDue(d.DueAt)
		}
		out = append(out, d)
		if len(out) >= 20 {
			break
		}
	}
	if len(out) == 0 {
		return nil, errors.New("AI_EMPTY_RESULT")
	}
	return out, nil
}

func validDateStr(s string) bool {
	_, e := time.Parse("2006-01-02", strings.TrimSpace(s))
	return e == nil
}

// normalizeTodoDue 接受 YYYY-MM-DDTHH:MM 或纯日期（补 18:00），其余返回空。
func normalizeTodoDue(s string) string {
	s = strings.TrimSpace(s)
	if s == "" {
		return ""
	}
	if _, e := time.Parse("2006-01-02T15:04", s); e == nil {
		return s
	}
	if validDateStr(s) {
		return s + "T18:00"
	}
	return ""
}