package gateway

// Agent-facing management API.
//
// The Web UI has always driven the gateway through /api/*, so the management
// surface already exists. What it lacked was anything an agent could *rely* on:
// no way to discover the contract, no single call that answers "what is the
// current state", and per-endpoint response shapes that make scripting brittle.
//
// This file adds a versioned, self-describing facade under /api/v1 without
// touching the existing endpoints, so the Web UI keeps working unchanged while
// agents get a stable contract:
//
//	GET    /api/v1                      — machine-readable index of every endpoint
//	GET    /api/v1/overview             — one call: sources + auto chain + keys + health
//	GET    /api/v1/sources              — sources, credentials masked
//	GET    /api/v1/sources/{name}       — one source
//	GET    /api/v1/auto                 — scheduling chain + live slot states
//	GET    /api/v1/keys                 — key metadata (never the secret)
//	GET    /api/v1/models               — every model id the gateway can route
//	GET    /api/v1/health               — per-source health, no auth needed beyond the key
//
// Auth is the same gateway key as everywhere else (Authorization: Bearer, or
// ?api_key=, or the gw_key cookie). Read endpoints accept any role; writes
// still require admin, enforced by the same middleware the UI goes through.

import (
	"errors"
	"net/http"
	"net/url"
	"sort"
	"strings"

	"llmsproxy/internal/config"
)

// apiV1Routes dispatches /api/v1/*. Kept separate from routes() so the original
// switch stays readable and the versioned surface can grow on its own.
func (g *Gateway) apiV1Routes(w http.ResponseWriter, r *http.Request) {
	path := strings.TrimPrefix(r.URL.Path, "/api/v1")
	path = strings.Trim(path, "/")

	switch {
	case path == "":
		g.apiV1Index(w, r)
	case path == "overview":
		g.apiV1Overview(w, r)
	case path == "health":
		g.apiV1Health(w, r)
	case path == "models":
		g.apiV1Models(w, r)
	case path == "sources":
		if r.Method != http.MethodGet {
			writeError(w, http.StatusMethodNotAllowed, "method_not_allowed", "use GET")
			return
		}
		writeJSON(w, http.StatusOK, map[string]interface{}{"sources": maskSources(g.core.Sources())})
	case strings.HasPrefix(path, "sources/"):
		name, err := decodePathSegment(strings.TrimPrefix(path, "sources/"))
		if err != nil {
			writeError(w, http.StatusBadRequest, "invalid_request", err.Error())
			return
		}
		if r.Method != http.MethodGet {
			writeError(w, http.StatusMethodNotAllowed, "method_not_allowed",
				"use PUT/DELETE on /api/sources/{name} to modify a source")
			return
		}
		for _, s := range g.core.Sources() {
			if s.Name == name {
				// ?reveal=credentials is admin-only and is what the Web UI's
				// edit dialog uses: a form that round-trips a source must be
				// able to show the current key, otherwise saving an unrelated
				// field would blank it. Everything else stays masked.
				if r.URL.Query().Get("reveal") == "credentials" {
					if reqRole(r.Context()) != "admin" {
						writeError(w, http.StatusForbidden, "forbidden",
							"admin role required to reveal credentials")
						return
					}
					writeJSON(w, http.StatusOK, map[string]interface{}{"source": s})
					return
				}
				writeJSON(w, http.StatusOK, map[string]interface{}{"source": maskSource(s)})
				return
			}
		}
		writeError(w, http.StatusNotFound, "not_found", "no such source: "+name)
	case path == "auto":
		if r.Method != http.MethodGet {
			writeError(w, http.StatusMethodNotAllowed, "method_not_allowed", "use GET")
			return
		}
		writeJSON(w, http.StatusOK, map[string]interface{}{
			"rules":       g.core.AutoRules(),
			"image_rules": g.core.AutoImageRules(),
			"states":      g.core.AutoSlotStates(),
		})
	case path == "keys":
		if reqRole(r.Context()) != "admin" {
			writeError(w, http.StatusForbidden, "forbidden", "admin role required")
			return
		}
		if r.Method != http.MethodGet {
			writeError(w, http.StatusMethodNotAllowed, "method_not_allowed",
				"use POST/PUT/DELETE on /api/keys to manage keys")
			return
		}
		keys := g.core.ListKeys()
		out := make([]map[string]interface{}, 0, len(keys))
		for _, k := range keys {
			out = append(out, map[string]interface{}{
				"name":       k.Name,
				"role":       k.Role,
				"models":     k.Models,
				"note":       k.Note,
				"created_at": k.CreatedAt,
				"seed":       k.Seed,
				// The secret itself is never echoed. An operator that needs it
				// already has it from creation time or from config.yaml.
				"key_prefix": maskKey(k.Key),
			})
		}
		writeJSON(w, http.StatusOK, map[string]interface{}{"keys": out})
	default:
		g.apiV1Index(w, r)
	}
}

// apiV1Index is the discovery document: it names every endpoint with its
// method, auth requirement and purpose, so an agent does not have to scrape the
// HTML to find out what it can call.
func (g *Gateway) apiV1Index(w http.ResponseWriter, r *http.Request) {
	type ep struct {
		Method      string `json:"method"`
		Path        string `json:"path"`
		Auth        string `json:"auth"`
		Summary     string `json:"summary"`
		WriteEffect string `json:"writes,omitempty"`
	}
	index := map[string]interface{}{
		"api_version": "v1",
		"description": "llmsproxy management API. Authenticate with a gateway key: " +
			"'Authorization: Bearer <key>', '?api_key=<key>', or the gw_key cookie. " +
			"Read endpoints accept any role; mutations require an admin key.",
		"discovery": []ep{
			{Method: "GET", Path: "/api/v1", Auth: "any", Summary: "this document"},
			{Method: "GET", Path: "/api/v1/overview", Auth: "any",
				Summary: "current state in one call: sources, auto chain, key count, source health"},
			{Method: "GET", Path: "/api/v1/health", Auth: "any",
				Summary: "per-source health snapshot only"},
			{Method: "GET", Path: "/api/v1/models", Auth: "any",
				Summary: "every model id the gateway can route, grouped by owning source"},
			{Method: "GET", Path: "/api/v1/sources", Auth: "any",
				Summary: "all sources with credentials masked"},
			{Method: "GET", Path: "/api/v1/sources/{name}", Auth: "any", Summary: "one source"},
			{Method: "GET", Path: "/api/v1/auto", Auth: "any",
				Summary: "AUTO scheduling chain and live per-slot state"},
			{Method: "GET", Path: "/api/v1/keys", Auth: "admin",
				Summary: "gateway key metadata; secrets are never returned"},

			{Method: "GET", Path: "/api/sources", Auth: "admin", Summary: "raw source list (includes api_key)"},
			{Method: "POST", Path: "/api/sources", Auth: "admin", Summary: "add or replace a source",
				WriteEffect: "writes config.yaml (api_key sealed at rest)"},
			{Method: "PUT", Path: "/api/sources/{name}", Auth: "admin", Summary: "update one source",
				WriteEffect: "writes config.yaml"},
			{Method: "DELETE", Path: "/api/sources/{name}", Auth: "admin", Summary: "delete a source",
				WriteEffect: "writes config.yaml"},

			{Method: "GET", Path: "/api/auto", Auth: "any", Summary: "scheduling chain (readable by any role)"},
			{Method: "PUT", Path: "/api/auto", Auth: "admin", Summary: "replace the scheduling chain",
				WriteEffect: "writes config.yaml (the AUTO chain lives here)"},

			{Method: "GET", Path: "/api/keys", Auth: "admin", Summary: "gateway keys"},
			{Method: "POST", Path: "/api/keys", Auth: "admin", Summary: "create a gateway key",
				WriteEffect: "writes config.yaml"},
			{Method: "DELETE", Path: "/api/keys/{name}", Auth: "admin", Summary: "delete a gateway key",
				WriteEffect: "writes config.yaml"},

			{Method: "GET", Path: "/api/status", Auth: "any", Summary: "per-source health detail"},
			{Method: "GET", Path: "/api/stats", Auth: "any", Summary: "usage aggregates"},
			{Method: "GET", Path: "/api/stats/records", Auth: "any", Summary: "paged request records"},
			{Method: "GET", Path: "/api/adapters", Auth: "admin", Summary: "installed Lua adapters"},
			{Method: "GET", Path: "/api/source_templates", Auth: "admin", Summary: "source templates"},
			{Method: "POST", Path: "/v1/chat/completions", Auth: "any", Summary: "OpenAI-compatible inference"},
		},
		"conventions": map[string]interface{}{
			"errors":       "{ \"error\": { \"type\": <code>, \"message\": <text> } }",
			"path_escape":  "URL-encode source and key names; {name} is a single path segment",
			"idempotency":  "POST /api/sources and PUT /api/sources/{name} both upsert by name",
			"config_truth": "all configuration lives in config.yaml; API writes are persisted immediately",
			"credentials": "credentials are masked by default. GET /api/v1/sources/{name}?reveal=credentials " +
				"returns them in the clear and is admin-only — the Web UI edit dialog uses it, because a form " +
				"that round-trips a source must show the current key or saving another field would blank it.",
		},
	}
	writeJSON(w, http.StatusOK, index)
}

// apiV1Overview is the "what is the current state" call an agent makes first.
// One round trip instead of five.
func (g *Gateway) apiV1Overview(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		writeError(w, http.StatusMethodNotAllowed, "method_not_allowed", "use GET")
		return
	}
	sources := g.core.Sources()
	names := make([]string, 0, len(sources))
	modelCount := 0
	for _, s := range sources {
		names = append(names, s.Name)
		modelCount += len(s.Models)
	}
	keys := g.core.ListKeys()
	adminCount, userCount := 0, 0
	for _, k := range keys {
		if k.Role == "admin" {
			adminCount++
		} else {
			userCount++
		}
	}
	writeJSON(w, http.StatusOK, map[string]interface{}{
		"api_version": "v1",
		"summary": map[string]interface{}{
			"source_count":      len(sources),
			"model_count":       modelCount,
			"gateway_key_count": len(keys),
			"admin_key_count":   adminCount,
			"user_key_count":    userCount,
			"auto_slots":        len(g.core.AutoRules()),
		},
		"sources":    maskSources(sources),
		"auto":       g.core.AutoRules(),
		"auto_image": g.core.AutoImageRules(),
		"health":     g.sourceHealthBrief(),
		"caller": map[string]interface{}{
			"role": reqRole(r.Context()),
			"key":  maskKey(reqKey(r.Context())),
		},
	})
}

func (g *Gateway) apiV1Health(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		writeError(w, http.StatusMethodNotAllowed, "method_not_allowed", "use GET")
		return
	}
	writeJSON(w, http.StatusOK, map[string]interface{}{"sources": g.sourceHealthBrief()})
}

// apiV1Models lists routable model ids per source, which is what an agent needs
// to build a valid request — /v1/models flattens them and hides the owner.
func (g *Gateway) apiV1Models(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		writeError(w, http.StatusMethodNotAllowed, "method_not_allowed", "use GET")
		return
	}
	bySource := map[string][]string{}
	var all []string
	for _, s := range g.core.Sources() {
		for _, m := range s.Models {
			bySource[s.Name] = append(bySource[s.Name], m.ID)
			all = append(all, m.ID)
		}
	}
	sort.Strings(all)
	all = dedupeStrings(all)
	writeJSON(w, http.StatusOK, map[string]interface{}{
		"count":     len(all),
		"models":    all,
		"by_source": bySource,
		"note":      "request a model as \"<source>:<model>\" to pin one source, or the bare id to let the gateway choose",
	})
}

// ---- helpers ----

// maskSources returns sources with credentials replaced by a presence marker.
// The UI still uses /api/sources (which returns real values, because its edit
// form round-trips them); this is the safe view for programmatic callers.
func maskSources(srcs []config.Source) []map[string]interface{} {
	out := make([]map[string]interface{}, 0, len(srcs))
	for _, s := range srcs {
		out = append(out, maskSource(s))
	}
	return out
}

func maskSource(s config.Source) map[string]interface{} {
	return map[string]interface{}{
		"name":           s.Name,
		"base_url":       s.BaseURL,
		"adapter":        s.Adapter,
		"endpoint":       s.Endpoint,
		"image_endpoint": s.ImageEndpoint,
		"api_key":        maskKey(s.APIKey),
		"api_key_set":    s.APIKey != "",
		"models":         s.Models,
		"headers":        maskHeaders(s.Headers),
		"proxy_url":      s.ProxyURL,
		"meta":           s.Meta,
		"temperature":    s.Temperature,
		"max_tokens":     s.MaxTokens,
		"max_concurrent": s.MaxConcurrent,
		"rpm":            s.RPM,
	}
}

func maskKey(k string) string {
	if k == "" {
		return ""
	}
	if strings.HasPrefix(k, "enc:v1:") {
		return "(sealed)"
	}
	if len(k) <= 10 {
		return k[:2] + "…"
	}
	return k[:6] + "…" + k[len(k)-4:]
}

func maskHeaders(h map[string]string) map[string]string {
	if h == nil {
		return nil
	}
	out := make(map[string]string, len(h))
	for k, v := range h {
		out[k] = maskKey(v)
	}
	return out
}

// sourceHealthBrief reuses the same registry status the UI's /api/status shows,
// so the agent view and the UI view cannot drift apart. Recent-traffic counters
// come from the same stats window, because a source that is actually serving
// traffic must never look down just because a probe was rate-limited.
func (g *Gateway) sourceHealthBrief() []map[string]interface{} {
	sts := g.core.Registry().Status()
	recent := g.stats.SourceRecent(300)
	avgs := g.stats.SourceAverages(300)
	for i := range sts {
		if v, ok := recent[sts[i].Name]; ok {
			sts[i].RecentOK = v[0]
			sts[i].RecentErr = v[1]
		}
		if a, ok := avgs[sts[i].Name]; ok {
			sts[i].AvgFirstByteMs = a.AvgFirstByteMs
			sts[i].AvgTokPerS = a.AvgTokPerS
		}
	}
	out := make([]map[string]interface{}, 0, len(sts))
	for _, s := range sts {
		row := map[string]interface{}{
			"name":           s.Name,
			"adapter":        s.Adapter,
			"healthy":        s.Healthy,
			"available":      s.Available,
			"live_available": s.LiveAvailable,
			"model_count":    len(s.Models),
		}
		if s.LastError != "" {
			row["last_error"] = s.LastError
		}
		if s.LastChecked > 0 {
			row["last_checked"] = s.LastChecked
		}
		if s.RecentOK > 0 || s.RecentErr > 0 {
			row["recent_ok"] = s.RecentOK
			row["recent_err"] = s.RecentErr
		}
		if s.AvgFirstByteMs > 0 {
			row["avg_first_byte_ms"] = s.AvgFirstByteMs
		}
		if s.AvgTokPerS > 0 {
			row["avg_tok_per_s"] = s.AvgTokPerS
		}
		if s.FailCount > 0 {
			row["fail_count"] = s.FailCount
		}
		if s.Permanent {
			row["permanent"] = true
		}
		out = append(out, row)
	}
	return out
}

// decodePathSegment URL-decodes one path segment and rejects an empty result,
// so a name containing a slash cannot be silently mis-resolved.
func decodePathSegment(seg string) (string, error) {
	s, err := url.PathUnescape(seg)
	if err != nil {
		return "", err
	}
	if s == "" {
		return "", errEmptySegment
	}
	return s, nil
}

func dedupeStrings(in []string) []string {
	out := in[:0]
	var last string
	for i, s := range in {
		if i == 0 || s != last {
			out = append(out, s)
		}
		last = s
	}
	return out
}

// errEmptySegment marks a path like /api/v1/sources/ with no name after it.
var errEmptySegment = errors.New("empty path segment")