// Package runtimeconfig loads and persists the runtime-editable provider
// configuration: the independent LLM vendor groups in models.json (design/04
// §3.1). The .env LLM block is the final fallback; a present-and-valid
// models.json takes precedence and is hot-reloaded at runtime without a restart.
//
// models.json is gitignored (local runtime config) and holds API keys, so this
// package never logs a key and never exposes one un-masked in a Config().
package runtimeconfig

import (
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"time"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/config"
)

// Provider names recognized in models.json. They mirror the model adapter
// factory's protocol names so a group maps directly to a wire protocol.
const (
	ProviderOpenAI    = "openai"
	ProviderAnthropic = "anthropic"

	// modelsFileName is the models.json basename stored under the data dir.
	modelsFileName = "models.json"
)

// ReasoningKind* 是 provider 级推理开关形状的合法取值（裁决 03.4.2 / 08.4.1：
// 不同提供商的思考开关形状各不相同，必须逐 provider 独立适配）。这些常量是
// 形状名的**唯一来源**：配置层（本包）校验它们，模型适配器按它们选 wire 字段，
// 面板按它们渲染下拉框。
//
// 取值刻意用**部署形态**命名（vllm / dashscope）而不是厂商名：同一家厂商的
// 模型在不同形态下的字段形状不同（vLLM 用 chat_template_kwargs.enable_thinking，
// DashScope 兼容模式用顶层 enable_thinking），形状由端点决定，不是由模型名决定。
const (
	// ReasoningKindAuto 是缺省值：按模型名/BaseURL 推断厂商，形状有歧义时
	// 不下发任何开关（只报告），因此它对旧配置零行为变化。
	ReasoningKindAuto = "auto"
	// ReasoningKindDeepSeek 是 DeepSeek：顶层 thinking:{type} + reasoning_effort。
	ReasoningKindDeepSeek = "deepseek"
	// ReasoningKindOpenAI 是 OpenAI 系：只有 reasoning_effort，无布尔开关。
	ReasoningKindOpenAI = "openai"
	// ReasoningKindVLLM 是 vLLM 类部署（承载 Qwen3 等）：
	// chat_template_kwargs.enable_thinking。
	ReasoningKindVLLM = "vllm"
	// ReasoningKindDashScope 是 DashScope 兼容模式：顶层 enable_thinking。
	ReasoningKindDashScope = "dashscope"
)

// ReasoningKinds 返回本 build 接受的 reasoning.kind 取值全集（auto 在首位，
// 与面板下拉框的推荐顺序一致）。它是**校验与面板的同一来源**：管理端点把这份
// 清单随配置一起下发，面板据此渲染下拉框，因此「面板能选的」与「配置层接受的」
// 不可能漂移。空串（未声明）不在此列——它是「不声明形状」而不是一个形状名，
// 面板另行给出该选项。返回新切片，调用方改不动包内状态。
func ReasoningKinds() []string {
	return []string{
		ReasoningKindAuto,
		ReasoningKindDeepSeek,
		ReasoningKindOpenAI,
		ReasoningKindVLLM,
		ReasoningKindDashScope,
	}
}

// ProviderNames 返回本 build 承认的 wire 协议名，用作 per-persona 路由
// （personaProviders）的合法值域。与面板共用同一来源，避免面板给出一个
// 配置层会拒收的协议名。
func ProviderNames() []string {
	return []string{ProviderOpenAI, ProviderAnthropic}
}

// ReasoningOptions 是一个 provider 组的推理开关形状声明。它是「按提供商
// 独立适配」的配置载体（裁决 03.4.2 / 08.4.1）：面板与 models.json 对每个
// 供应商各写一份，因此 vLLM 端点与 DashScope 端点可以同时存在、各自下发
// 自己形状的开关，而不是被套进一个「通用」形状。默认（零值）保守：不声明
// 形状就不下发开关，只报告——发错形状会 400，比不发更糟。
type ReasoningOptions struct {
	// Kind 显式声明该端点的思考开关形状（见 ReasoningKind* 常量）。
	// 空或 "auto" = 按模型名/BaseURL 推断厂商（形状有歧义时不下发）。
	Kind string `json:"kind,omitempty"`
}

// Group is one independent multi-supplier LLM configuration. Each vendor's
// base/key/model/fallback is a self-contained unit, so multiple vendors coexist
// and Provider selects the active wire protocol.
type Group struct {
	ID         string `json:"id"`
	Provider   string `json:"provider"`
	BaseURL    string `json:"baseUrl"`
	APIKey     string `json:"apiKey"`
	Model      string `json:"model"`
	Fallback   string `json:"fallback,omitempty"`
	Multimodal bool   `json:"multimodal,omitempty"`
	// MaxTokens is the group's own token budget, applied to every model in the
	// group's fallback chain (primary and fallback). Zero means "unset": the
	// last-resort fallback step then falls back to LLM_FALLBACK_MAX_TOKENS, and
	// beyond that the adapter default applies.
	MaxTokens int `json:"maxTokens,omitempty"`
	// ContextWindow 声明本组的模型上下文窗口（token）。它是**声明式**的窗口来源
	// （design/04 附录 A.3 第 1 条）：本仓没有任何 provider 侧窗口发现代码，而
	// 上下文溢出压缩预算要按窗口推导（config.DeriveContextBudget），因此窗口必须
	// 由人来声明。0（默认，键被省略）= 未声明，推导回落到
	// config.DefaultModelContextWindow 并记一条 WARN；负数在校验阶段报错。
	//
	// 它是 `.env` 侧 LLM_CONTEXT_WINDOW 的对偶（per-group 播种，见 materialize.go）。
	ContextWindow int `json:"contextWindow,omitempty"`
	// PersonaModels binds an individual persona to its own model name within this
	// group (裁决 03.4.1: the "role" of per-role routing is the persona a turn
	// answers as, not the LLM message role). The carrier is deliberately
	// models.json rather than configs/personas/*.yaml, so the panel can edit the
	// binding together with the rest of the provider configuration and no persona
	// schema change is needed. An unknown persona id falls back to the group's
	// default model, so a removed persona never breaks routing.
	PersonaModels map[string]string `json:"personaModels,omitempty"`
	// PersonaProviders binds an individual persona to another vendor's protocol
	// (裁决 03.4.1 的 per-persona provider). Pair it with PersonaModels; an entry
	// without a provider keeps this group's protocol.
	PersonaProviders map[string]string `json:"personaProviders,omitempty"`
	// Reasoning declares this provider/endpoint's reasoning-switch wire shape
	// (裁决 03.4.2 / 08.4.1). It is a provider-level option because the shape
	// belongs to the endpoint, not to a persona: every group carries its own, so
	// two vendors with different switch shapes coexist without a shared guess.
	// omitzero keeps an undeclared shape out of models.json entirely (an empty
	// object would be schema noise for every group).
	Reasoning ReasoningOptions `json:"reasoning,omitzero"`
}

// ErrInvalidGroup is returned when a group fails schema validation.
var ErrInvalidGroup = errors.New("runtimeconfig: invalid model group")

// DefaultPath returns the models.json path under dataDir.
func DefaultPath(dataDir string) string {
	return filepath.Join(dataDir, modelsFileName)
}

// Validate checks the group's required fields. It fails loudly so a bad group
// never silently produces a half-configured adapter.
func (g Group) Validate() error {
	if strings.TrimSpace(g.ID) == "" {
		return fmt.Errorf("id is required")
	}
	if g.Provider != ProviderOpenAI && g.Provider != ProviderAnthropic {
		return fmt.Errorf("provider %q must be openai or anthropic", g.Provider)
	}
	if strings.TrimSpace(g.BaseURL) == "" {
		return fmt.Errorf("baseUrl is required")
	}
	if strings.TrimSpace(g.Model) == "" {
		return fmt.Errorf("model is required")
	}
	if g.MaxTokens < 0 {
		return fmt.Errorf("maxTokens must be >= 0, got %d", g.MaxTokens)
	}
	if g.ContextWindow < 0 {
		return fmt.Errorf("contextWindow must be >= 0 (0 = 未声明，按回落窗口推导), got %d", g.ContextWindow)
	}
	if err := validatePersonaMap("personaModels", g.PersonaModels, false); err != nil {
		return err
	}
	if err := validatePersonaMap("personaProviders", g.PersonaProviders, true); err != nil {
		return err
	}
	return validateReasoning(g.Provider, g.Reasoning)
}

// validateReasoning checks a provider-level reasoning shape declaration. A blank
// or "auto" kind is always valid (the conservative default: infer from the model
// name/base URL, and send nothing when the shape is ambiguous). Any other kind
// must be a shape this build implements and has evidence for; and the
// openai-compatible shape names are rejected on an anthropic group, whose switch
// shape is defined by its own protocol — failing loudly beats a silently inert
// option.
func validateReasoning(provider string, r ReasoningOptions) error {
	kind := strings.TrimSpace(r.Kind)
	switch kind {
	case "", ReasoningKindAuto, ReasoningKindDeepSeek, ReasoningKindOpenAI,
		ReasoningKindVLLM, ReasoningKindDashScope:
	default:
		return fmt.Errorf("reasoning.kind %q must be one of %s", kind, strings.Join(ReasoningKinds(), "/"))
	}
	if provider == ProviderAnthropic && kind != "" && kind != ReasoningKindAuto {
		return fmt.Errorf("reasoning.kind %q applies to the openai-compatible provider only", kind)
	}
	return nil
}

// validatePersonaMap checks a persona-keyed binding map: every key must be a
// non-empty persona id and every value a non-empty value. When providers is true
// the values must additionally be a known protocol, so a typo in a per-persona
// provider fails the group loudly instead of silently routing to the default.
func validatePersonaMap(field string, m map[string]string, providers bool) error {
	for persona, value := range m {
		if strings.TrimSpace(persona) == "" {
			return fmt.Errorf("%s: persona id must not be empty", field)
		}
		if strings.TrimSpace(value) == "" {
			return fmt.Errorf("%s: value for persona %q must not be empty", field, persona)
		}
		if providers && value != ProviderOpenAI && value != ProviderAnthropic {
			return fmt.Errorf("%s: provider %q for persona %q must be openai or anthropic", field, value, persona)
		}
	}
	return nil
}

// PersonaRoute returns the per-persona model/provider binding, if one is
// configured for persona. An empty model (or an unknown persona) is reported as
// ok=false so the caller keeps the group's default binding.
func (g Group) PersonaRoute(persona string) (model, provider string, ok bool) {
	persona = strings.TrimSpace(persona)
	if persona == "" {
		return "", "", false
	}
	model = strings.TrimSpace(g.PersonaModels[persona])
	if model == "" {
		return "", "", false
	}
	return model, strings.TrimSpace(g.PersonaProviders[persona]), true
}

// ToLLMConfig maps a group to the flat LLMConfig consumed by the adapter
// factory. The group's provider selects which config block is populated.
func (g Group) ToLLMConfig() config.LLMConfig {
	if g.Provider == ProviderAnthropic {
		return config.LLMConfig{
			Provider:          ProviderAnthropic,
			AnthropicBaseURL:  g.BaseURL,
			AnthropicAPIKey:   g.APIKey,
			AnthropicModel:    g.Model,
			AnthropicFallback: g.Fallback,
			ReasoningKind:     strings.TrimSpace(g.Reasoning.Kind),
		}
	}
	return config.LLMConfig{
		Provider:      ProviderOpenAI,
		BaseURL:       g.BaseURL,
		APIKey:        g.APIKey,
		Model:         g.Model,
		Fallback:      g.Fallback,
		ReasoningKind: strings.TrimSpace(g.Reasoning.Kind),
	}
}

// MaskedKey returns a redacted form of the API key for display/logging. It never
// reveals more than the trailing 4 characters, so a key never lands verbatim in
// a log line or a wire response.
func (g Group) MaskedKey() string {
	k := strings.TrimSpace(g.APIKey)
	if k == "" {
		return ""
	}
	if len(k) <= 4 {
		return "****"
	}
	return "****" + k[len(k)-4:]
}

// LoadModels reads path and returns the effective LLM groups. When the file is
// absent it synthesizes a single group from env (the .env fallback). A
// present-but-invalid file falls back to env and returns a non-nil warning so
// the caller can log it; the returned groups are always non-empty.
func LoadModels(path string, env config.LLMConfig) ([]Group, error) {
	files, readErr := loadFile(path)
	if readErr == nil {
		return files, nil
	}
	// A missing file is the normal case (gitignored runtime config); only a
	// present-but-invalid file warrants a warning to the caller.
	var warn error
	if !os.IsNotExist(readErr) {
		warn = fmt.Errorf("runtimeconfig: %s: %w", path, readErr)
	}
	return GroupFromEnv(env), warn
}

// loadFile decodes and validates the models.json array. A nil/blank file, a
// JSON decode error or an empty array all return an error so the caller falls
// back to env.
func loadFile(path string) ([]Group, error) {
	raw, err := os.ReadFile(path)
	if err != nil {
		return nil, err
	}
	if len(strings.TrimSpace(string(raw))) == 0 {
		return nil, fmt.Errorf("%w: empty file", ErrInvalidGroup)
	}
	var groups []Group
	dec := json.NewDecoder(strings.NewReader(string(raw)))
	if err := dec.Decode(&groups); err != nil {
		return nil, fmt.Errorf("%w: decode: %v", ErrInvalidGroup, err)
	}
	if len(groups) == 0 {
		return nil, fmt.Errorf("%w: no groups", ErrInvalidGroup)
	}
	for i, g := range groups {
		if err := g.Validate(); err != nil {
			return nil, fmt.Errorf("%w: group %d: %v", ErrInvalidGroup, i, err)
		}
	}
	return groups, nil
}

// GroupFromEnv synthesizes a single group from the active env LLM block: the
// anthropic block when LLM_PROVIDER=anthropic, otherwise the flat OpenAI-compatible
// block. It is the .env fallback used when models.json is absent or invalid.
//
// Multimodal 来自 LLM_MULTIMODAL，默认 false。语义（裁决 14.4.1）：它是本组
// `multimodal` 字段的 **env 声明**——「主模型自身能否收图」，而不是「本部署有没有
// 视觉能力」。默认 false 与引入本键之前的行为逐字节一致：
// 扁平 env 块只有这一个键能声明收图能力，而**声称端点可能不具备的能力，比把图
// 交给 vision/OCR 工具更糟**——工具至少会返回一段文本描述（design/06 §0 首条）。
// 因此只有显式写 `LLM_MULTIMODAL=true` 才让主模型直接收图，**绝不凭 baseURL /
// 模型名猜测**（与 reasoning.kind 的口径一致：声明才生效，不推断）。LLM_VISION_MODEL
// / LLM_OCR_MODEL 配的是**视觉/OCR 工具调用的模型**，与本组能否收图互不代表。
//
// 非法值（不是 bool，如 `maybe`）在 config.Load 解码阶段**直接报错**，启动失败，
// 不静默回退成 false——静默的「配了当没配」正是本键要消灭的东西。
//
// Reasoning.Kind is carried through so an env-only deployment can still declare
// its endpoint's switch shape (LLM_REASONING_KIND); its env default is blank,
// which keeps every existing deployment at "auto" (no new field is ever sent).
func GroupFromEnv(env config.LLMConfig) []Group {
	if env.Provider == ProviderAnthropic {
		return []Group{{
			ID:            ProviderAnthropic,
			Provider:      ProviderAnthropic,
			BaseURL:       env.AnthropicBaseURL,
			APIKey:        env.AnthropicAPIKey,
			Model:         env.AnthropicModel,
			Fallback:      env.AnthropicFallback,
			Multimodal:    env.Multimodal,
			ContextWindow: env.ContextWindow,
			Reasoning:     ReasoningOptions{Kind: strings.TrimSpace(env.ReasoningKind)},
		}}
	}
	return []Group{{
		ID:            ProviderOpenAI,
		Provider:      ProviderOpenAI,
		BaseURL:       env.BaseURL,
		APIKey:        env.APIKey,
		Model:         env.Model,
		Fallback:      env.Fallback,
		Multimodal:    env.Multimodal,
		ContextWindow: env.ContextWindow,
		Reasoning:     ReasoningOptions{Kind: strings.TrimSpace(env.ReasoningKind)},
	}}
}

// Find returns the group with the given id, if present. It is the read half of
// the admin read-modify-write merge, so a partial edit starts from the stored
// group instead of zero values.
func Find(groups []Group, id string) (Group, bool) {
	if strings.TrimSpace(id) == "" {
		return Group{}, false
	}
	for _, g := range groups {
		if g.ID == id {
			return g, true
		}
	}
	return Group{}, false
}

// Upsert returns a copy of groups with g inserted or replaced in place by ID,
// preserving order. A blank ID is assigned a generated id so a panel save
// without an explicit id still produces a stable, addressable group.
func Upsert(groups []Group, g Group) []Group {
	if strings.TrimSpace(g.ID) == "" {
		g.ID = NewID()
	}
	out := make([]Group, 0, len(groups)+1)
	replaced := false
	for _, cur := range groups {
		if cur.ID == g.ID {
			out = append(out, g)
			replaced = true
			continue
		}
		out = append(out, cur)
	}
	if !replaced {
		out = append(out, g)
	}
	return out
}

// Activate returns groups with g promoted to the front (index 0 = the group a
// new request uses by default). An existing group with the same id is replaced
// and re-prepended, so a panel save both updates the group and makes it the live
// provider. A blank ID is assigned a generated id.
func Activate(groups []Group, g Group) []Group {
	if strings.TrimSpace(g.ID) == "" {
		g.ID = NewID()
	}
	out := make([]Group, 0, len(groups)+1)
	out = append(out, g)
	for _, cur := range groups {
		if cur.ID == g.ID {
			continue
		}
		out = append(out, cur)
	}
	return out
}

// SaveModels writes groups as a pretty-printed JSON array to path with mode
// 0600 (the file holds API keys). It writes to a temp file then renames so a
// concurrent reader never sees a partial file. Every group is validated first.
func SaveModels(path string, groups []Group) error {
	dir := filepath.Dir(path)
	if dir != "" && dir != "." {
		if err := os.MkdirAll(dir, 0o755); err != nil {
			return fmt.Errorf("runtimeconfig: mkdir: %w", err)
		}
	}
	for _, g := range groups {
		if err := g.Validate(); err != nil {
			return fmt.Errorf("runtimeconfig: save: %w", err)
		}
	}
	raw, err := json.MarshalIndent(groups, "", "  ")
	if err != nil {
		return fmt.Errorf("runtimeconfig: marshal: %w", err)
	}
	tmp := path + ".tmp"
	if err := os.WriteFile(tmp, raw, 0o600); err != nil {
		return fmt.Errorf("runtimeconfig: write %s: %w", tmp, err)
	}
	if err := os.Rename(tmp, path); err != nil {
		return fmt.Errorf("runtimeconfig: rename: %w", err)
	}
	return nil
}

// NewID returns a 16-byte hex id, used for a group saved without an explicit id.
func NewID() string {
	b := make([]byte, 16)
	if _, err := rand.Read(b); err != nil {
		return fmt.Sprintf("id-%d", newTimeUnixNano())
	}
	return hex.EncodeToString(b)
}

// newTimeUnixNano returns the current unix-nano as an integer, as a fallback id
// source when the crypto RNG fails.
func newTimeUnixNano() int64 {
	return time.Now().UnixNano()
}