package service

import (
	"net/http"
	"slices"
	"strings"

	"github.com/Wei-Shaw/sub2api/internal/domain"
	"github.com/Wei-Shaw/sub2api/internal/pkg/claude"
	infraerrors "github.com/Wei-Shaw/sub2api/internal/pkg/errors"
	"github.com/Wei-Shaw/sub2api/internal/pkg/openai"
)

// GroupModelAllowlist 是 service 层的分组模型白名单（与 domain.GroupModelAllowlist
// 字段一致，ent 持久化用 domain 类型，边界处显式转换）。
type GroupModelAllowlist struct {
	Enabled bool     `json:"enabled"`
	Models  []string `json:"models,omitempty"`
}

// DomainGroupModelAllowlist 把 service 白名单转换为 ent 持久化使用的 domain 类型。
func DomainGroupModelAllowlist(cfg GroupModelAllowlist) domain.GroupModelAllowlist {
	return domain.GroupModelAllowlist{Enabled: cfg.Enabled, Models: cfg.Models}
}

// GroupModelAllowlistFromDomain 把 ent 读出的 domain 白名单转换为 service 类型。
func GroupModelAllowlistFromDomain(cfg domain.GroupModelAllowlist) GroupModelAllowlist {
	return GroupModelAllowlist{Enabled: cfg.Enabled, Models: cfg.Models}
}

// supplementUnmappedOpenAIModels ensures a partial mapping catalog does not
// hide models from unmapped OpenAI accounts. An empty catalog is left unchanged
// so callers retain their existing discovery fallback.
func supplementUnmappedOpenAIModels(accounts []Account, models []string) []string {
	if len(models) == 0 {
		return models
	}
	for i := range accounts {
		account := &accounts[i]
		if account.Platform == PlatformOpenAI && len(account.GetModelMapping()) == 0 {
			return dedupeAndSortModelIDs(slices.Concat(models, openai.DefaultModelIDs()))
		}
	}
	return models
}

// normalizeGroupModelAllowlist 归一化管理端提交的分组模型白名单：
// 条目 TrimSpace、按小写去重保序；`*` 只允许出现在条目末尾；
// enabled=true 且列表为空视为配置错误，返回 400 而不是运行时静默放行/拒绝。
func normalizeGroupModelAllowlist(cfg GroupModelAllowlist) (GroupModelAllowlist, error) {
	out := GroupModelAllowlist{Enabled: cfg.Enabled}
	if len(cfg.Models) == 0 {
		if out.Enabled {
			return out, infraerrors.New(http.StatusBadRequest, "INVALID_MODEL_ALLOWLIST", "model allowlist cannot be enabled with an empty model list")
		}
		return out, nil
	}

	seen := make(map[string]struct{}, len(cfg.Models))
	out.Models = make([]string, 0, len(cfg.Models))
	for _, model := range cfg.Models {
		model = strings.TrimSpace(model)
		if model == "" {
			continue
		}
		if strings.Contains(strings.TrimSuffix(model, "*"), "*") {
			return out, infraerrors.New(http.StatusBadRequest, "INVALID_MODEL_ALLOWLIST", `wildcard "*" is only allowed at the end of an allowlist entry`)
		}
		key := strings.ToLower(model)
		if _, ok := seen[key]; ok {
			continue
		}
		seen[key] = struct{}{}
		out.Models = append(out.Models, model)
	}
	if len(out.Models) == 0 {
		if out.Enabled {
			return out, infraerrors.New(http.StatusBadRequest, "INVALID_MODEL_ALLOWLIST", "model allowlist cannot be enabled with an empty model list")
		}
		out.Models = nil
	}
	return out, nil
}

// ModelAllowlistEnabled 报告该分组是否启用了模型白名单。
// 开启后所有携带模型的网关请求与模型列表接口都受白名单约束。
func (g *Group) ModelAllowlistEnabled() bool {
	return g != nil && g.ModelAllowlist.Enabled
}

// Allows 判断客户端请求的模型是否命中白名单。
// 准入只看客户端书写的模型名，与账号映射、渠道映射、合成路由改写无关；
// 候选形式覆盖代码中已有的模型名等价规则（Gemini models/ 前缀、
// Antigravity/Claude -thinking 宽容规则、OpenAI 推理后缀），不做模糊匹配。
func (a GroupModelAllowlist) Allows(model string) bool {
	if !a.Enabled {
		return true
	}
	model = strings.TrimSpace(model)
	if model == "" {
		return true
	}
	candidates := groupModelAllowlistCandidates(model)
	for _, entry := range a.Models {
		entry = strings.TrimSpace(entry)
		if entry == "" {
			continue
		}
		entry = strings.ToLower(entry)
		if strings.HasSuffix(entry, "*") {
			prefix := strings.TrimSuffix(entry, "*")
			for _, candidate := range candidates {
				if strings.HasPrefix(candidate, prefix) {
					return true
				}
			}
			continue
		}
		for _, candidate := range candidates {
			if candidate == entry {
				return true
			}
		}
	}
	return false
}

// groupModelAllowlistCandidates 返回客户端模型名在白名单匹配中的候选形式（均已小写）。
func groupModelAllowlistCandidates(model string) []string {
	candidates := make([]string, 0, 4)
	add := func(value string) {
		value = strings.ToLower(strings.TrimSpace(value))
		if value == "" {
			return
		}
		for _, existing := range candidates {
			if existing == value {
				return
			}
		}
		candidates = append(candidates, value)
	}

	add(model)
	add(strings.TrimPrefix(model, "models/"))
	add(claude.NormalizeModelID(strings.TrimSuffix(model, "-thinking")))
	add(NormalizeOpenAICompatRequestedModel(model))
	return candidates
}

// FilterForListing 按白名单条目顺序生成模型列表输出。
// 精确条目沿用既有规则：只有出现在 source（账号映射键 ∪ 平台默认列表）的模式
// 集合中才输出；通配条目展开为 source 中所有匹配项并保持 source 顺序；全局去重。
func (a GroupModelAllowlist) FilterForListing(source []string) []string {
	if !a.Enabled {
		return source
	}
	if len(a.Models) == 0 {
		// 开启但为空的配置在管理端已被拒绝；对遗留脏数据保持“看到什么 = 能调什么”，
		// 列表与准入同时返回空。
		return nil
	}

	patterns := make([]string, 0, len(source))
	for _, pattern := range source {
		pattern = strings.TrimSpace(pattern)
		if pattern != "" {
			patterns = append(patterns, pattern)
		}
	}
	if len(patterns) == 0 {
		return nil
	}

	seen := make(map[string]struct{}, len(a.Models)+len(patterns))
	filtered := make([]string, 0, len(patterns))
	add := func(model string) {
		key := strings.ToLower(model)
		if _, ok := seen[key]; ok {
			return
		}
		seen[key] = struct{}{}
		filtered = append(filtered, model)
	}

	for _, entry := range a.Models {
		entry = strings.TrimSpace(entry)
		if entry == "" {
			continue
		}
		if strings.HasSuffix(entry, "*") {
			// 空 前缀（裸 `*` 条目）匹配全部来源，与 Allows 的全放行语义一致。
			prefix := strings.ToLower(strings.TrimSuffix(entry, "*"))
			for _, pattern := range patterns {
				if strings.HasPrefix(strings.ToLower(pattern), prefix) {
					add(pattern)
				}
			}
			continue
		}
		if allowlistSourcePatternAllowsModel(patterns, entry) {
			add(entry)
		}
	}
	return filtered
}

// allowlistSourcePatternAllowsModel 沿用 filterModelsByCustomList 时代的匹配规则：
// 精确相等、source 通配模式的前缀匹配，以及 Claude 归一化（-thinking 后缀）
// 后的精确匹配。比较与 Allows 一律大小写不敏感，保证「准入允许 ⇒ 列表可见」。
func allowlistSourcePatternAllowsModel(patterns []string, model string) bool {
	for _, pattern := range patterns {
		if strings.EqualFold(pattern, model) {
			return true
		}
		if strings.HasSuffix(pattern, "*") && strings.HasPrefix(strings.ToLower(model), strings.ToLower(strings.TrimSuffix(pattern, "*"))) {
			return true
		}
	}
	normalizedClaudeModel := claude.NormalizeModelID(strings.TrimSuffix(model, "-thinking"))
	if !strings.EqualFold(normalizedClaudeModel, model) {
		for _, pattern := range patterns {
			if strings.EqualFold(pattern, normalizedClaudeModel) {
				return true
			}
		}
	}
	return false
}