package rules

import (
	"errors"
	"fmt"
	"strings"

	"git.yeij.top/AskaEth/Scoreboard/server/internal/domain"
)

// 哨兵错误：调用方据此区分「格式不对」「版本不兼容」「内容非法」。
var (
	ErrNotRulePack         = errors.New("rules: 不是积分规则包")
	ErrIncompatibleVersion = errors.New("rules: 规则包格式版本不兼容")
	ErrValidation          = errors.New("rules: 规则包校验失败")
	ErrProfileInUse        = errors.New("rules: 积分模板仍被引用，不能删除")
	ErrNilChangeSet        = errors.New("rules: 变更集或目标规则包为空，无法导入")
)

// Issue 是一条校验问题；Path 用点号路径定位到 YAML 中的位置。
type Issue struct {
	Path string `json:"path"`
	Msg  string `json:"msg"`
}

// ValidationError 汇总一次校验中的全部问题，避免「改一个报一个」。
type ValidationError struct {
	Issues []Issue `json:"issues"`
}

func (e *ValidationError) Error() string {
	if len(e.Issues) == 0 {
		return ErrValidation.Error()
	}
	parts := make([]string, 0, len(e.Issues))
	for _, is := range e.Issues {
		parts = append(parts, is.Path+": "+is.Msg)
	}
	return ErrValidation.Error() + ": " + strings.Join(parts, "; ")
}

// Unwrap 让 errors.Is(err, ErrValidation) 成立。
func (e *ValidationError) Unwrap() error { return ErrValidation }

type issueList struct {
	issues []Issue
}

func (l *issueList) addf(path, format string, args ...any) {
	l.issues = append(l.issues, Issue{Path: path, Msg: fmt.Sprintf(format, args...)})
}

// Validate 校验规则包。格式 / 版本不符立即返回哨兵错误，其余问题一次性汇总。
func (p *RulePack) Validate() error {
	if p.Format != FormatName {
		return fmt.Errorf("%w: format=%q，期望 %q", ErrNotRulePack, p.Format, FormatName)
	}
	if p.FormatVersion != FormatVersion {
		return fmt.Errorf("%w: formatVersion=%d，本程序只支持 %d，不做隐式转换",
			ErrIncompatibleVersion, p.FormatVersion, FormatVersion)
	}

	var l issueList
	if strings.TrimSpace(p.Meta.Code) == "" {
		l.addf("meta.code", "不能为空")
	}
	if strings.TrimSpace(p.Meta.Name) == "" {
		l.addf("meta.name", "不能为空")
	}

	if p.Standings.IndividualToTeamWeight < 0 {
		l.addf("standings.individualToTeamWeight", "不能为负，当前 %v", p.Standings.IndividualToTeamWeight)
	}
	validateTieBreak(&l, p.Standings.TieBreak)

	profiles := make(map[string]bool, len(p.Profiles))
	if len(p.Profiles) == 0 {
		l.addf("profiles", "至少要有一个积分模板")
	}
	for i, prof := range p.Profiles {
		path := fmt.Sprintf("profiles[%d]", i)
		validateProfile(&l, path, prof, profiles)
	}

	validateRecordBonus(&l, p.RecordBonus)
	validateTemplates(&l, p.ChannelTemplates, profiles)
	validateOverrides(&l, p.EventOverrides, profiles)

	if len(l.issues) > 0 {
		return &ValidationError{Issues: l.issues}
	}
	return nil
}

func validateTieBreak(l *issueList, tieBreak []string) {
	seen := make(map[string]bool, len(tieBreak))
	for i, key := range tieBreak {
		path := fmt.Sprintf("standings.tieBreak[%d]", i)
		if !knownTieBreakKeys[key] {
			l.addf(path, "未知的排序键 %q", key)
			continue
		}
		if seen[key] {
			l.addf(path, "排序键 %q 重复", key)
		}
		seen[key] = true
	}
}

func validateProfile(l *issueList, path string, prof Profile, seen map[string]bool) {
	if strings.TrimSpace(prof.Code) == "" {
		l.addf(path+".code", "不能为空")
	} else if seen[prof.Code] {
		l.addf(path+".code", "模板编码 %q 重复", prof.Code)
	} else {
		seen[prof.Code] = true
	}
	if strings.TrimSpace(prof.Name) == "" {
		l.addf(path+".name", "不能为空")
	}
	if prof.AwardRanks < 0 {
		l.addf(path+".awardRanks", "不能为负，当前 %d", prof.AwardRanks)
	}
	if prof.TieMode != domain.TieSkip && prof.TieMode != domain.TieAverage && prof.TieMode != domain.TieHigher {
		l.addf(path+".tieMode", "只能是 skip / average / higher，当前 %q", prof.TieMode)
	}
	if prof.RecordBonusMode != "" && prof.RecordBonusMode != domain.RecordBonusMax && prof.RecordBonusMode != domain.RecordBonusSum {
		l.addf(path+".recordBonusMode", "只能是 max / sum，当前 %q", prof.RecordBonusMode)
	}
	if prof.AwardRanks > 0 && len(prof.Rules) == 0 {
		l.addf(path+".rules", "awardRanks=%d 却没有分值明细", prof.AwardRanks)
	}
	ranks := make(map[int]bool, len(prof.Rules))
	for j, r := range prof.Rules {
		rpath := fmt.Sprintf("%s.rules[%d]", path, j)
		if r.Rank < 1 {
			l.addf(rpath+".rank", "名次必须 >= 1，当前 %d", r.Rank)
		} else if ranks[r.Rank] {
			l.addf(rpath+".rank", "名次 %d 重复", r.Rank)
		}
		ranks[r.Rank] = true
		if r.Points < 0 {
			l.addf(rpath+".points", "分值不能为负，当前 %v", r.Points)
		}
	}
}

func validateRecordBonus(l *issueList, rb RecordBonus) {
	if rb.Mode != "" && rb.Mode != domain.RecordBonusMax && rb.Mode != domain.RecordBonusSum {
		l.addf("recordBonus.mode", "只能是 max / sum，当前 %q", rb.Mode)
	}
	if rb.Enabled && len(rb.Levels) == 0 {
		l.addf("recordBonus.levels", "启用破纪录加分却没有配置档位")
	}
	seen := make(map[string]bool, len(rb.Levels))
	for i, lv := range rb.Levels {
		path := fmt.Sprintf("recordBonus.levels[%d]", i)
		if strings.TrimSpace(lv.Code) == "" {
			l.addf(path+".code", "不能为空")
		} else if seen[lv.Code] {
			l.addf(path+".code", "档位编码 %q 重复", lv.Code)
		} else {
			seen[lv.Code] = true
		}
		if strings.TrimSpace(lv.Name) == "" {
			l.addf(path+".name", "不能为空")
		}
		if lv.Points < 0 {
			l.addf(path+".points", "分值不能为负，当前 %v", lv.Points)
		}
	}
}

func validateTemplates(l *issueList, templates []ChannelTemplate, profiles map[string]bool) {
	seen := make(map[string]bool, len(templates))
	for i, t := range templates {
		path := fmt.Sprintf("channelTemplates[%d]", i)
		key := matchKey(t.Match)
		if key == "" {
			l.addf(path+".match", "至少要指定 eventType / resultType / sportCode 之一")
		} else if seen[key] {
			l.addf(path+".match", "匹配条件 %s 重复", key)
		}
		seen[key] = true
		if len(t.Channels) == 0 {
			l.addf(path+".channels", "模板至少要有一个计分通道")
		}
		validateChannels(l, path+".channels", t.Channels, profiles)
	}
}

func validateOverrides(l *issueList, overrides []EventOverride, profiles map[string]bool) {
	seen := make(map[string]bool, len(overrides))
	for i, o := range overrides {
		path := fmt.Sprintf("eventOverrides[%d]", i)
		if strings.TrimSpace(o.EventCode) == "" {
			l.addf(path+".eventCode", "不能为空")
		} else if seen[o.EventCode] {
			l.addf(path+".eventCode", "项目编码 %q 重复", o.EventCode)
		} else {
			seen[o.EventCode] = true
		}
		if o.Multiplier != nil && *o.Multiplier < 0 {
			l.addf(path+".multiplier", "不能为负，当前 %v", *o.Multiplier)
		}
		if o.Channels != nil {
			validateChannels(l, path+".channels", *o.Channels, profiles)
		}
	}
}

func validateChannels(l *issueList, path string, channels []Channel, profiles map[string]bool) {
	seen := make(map[string]bool, len(channels))
	for i, ch := range channels {
		cpath := fmt.Sprintf("%s[%d]", path, i)
		if ch.Scope != domain.ScopeAthlete && ch.Scope != domain.ScopeTeam {
			l.addf(cpath+".scope", "只能是 athlete / team，当前 %q", ch.Scope)
		}
		switch ch.Basis {
		case domain.BasisResult, domain.BasisManual, domain.BasisAggregate:
		default:
			l.addf(cpath+".basis", "只能是 result / manual / aggregate，当前 %q", ch.Basis)
		}
		if strings.TrimSpace(ch.Profile) == "" {
			l.addf(cpath+".profile", "不能为空")
		} else if !profiles[ch.Profile] {
			l.addf(cpath+".profile", "引用了不存在的积分模板 %q", ch.Profile)
		}
		// 落库有 UNIQUE(event_id, scope, basis) 约束，这里先挡住，避免导入时才炸。
		key := string(ch.Scope) + "/" + string(ch.Basis)
		if seen[key] {
			l.addf(cpath, "同一组配置里出现重复通道 %s", key)
		}
		seen[key] = true
	}
}

func matchKey(m ChannelMatch) string {
	var parts []string
	if m.EventType != "" {
		parts = append(parts, "eventType="+string(m.EventType))
	}
	if m.ResultType != "" {
		parts = append(parts, "resultType="+string(m.ResultType))
	}
	if m.SportCode != "" {
		parts = append(parts, "sportCode="+m.SportCode)
	}
	return strings.Join(parts, ",")
}

func matchEvent(m ChannelMatch, e EventInfo) bool {
	if m.EventType != "" && m.EventType != e.EventType {
		return false
	}
	if m.ResultType != "" && m.ResultType != e.ResultType {
		return false
	}
	if m.SportCode != "" && m.SportCode != e.SportCode {
		return false
	}
	return true
}