// V15.4 — Ollama Cloud dynamic context-length sync.
//
// Why: the static map in context_limits.go has to be hand-maintained
// for every new Ollama Cloud model. Cloud ships new models monthly,
// and a missing entry silently disables compaction for runs on that
// model (compactionThresholdForModel returns 0 on MaxContextTokens
// miss). Dynamic sync removes the maintenance burden and means new
// cloud models work out-of-the-box.
//
// How: at boot, mort kicks off a CloudOllamaLimitCache.RefreshAll in a
// background goroutine. RefreshAll calls /api/tags to list every
// available cloud model, then concurrently calls /api/show for each
// to extract `<family>.context_length` from the response's model_info
// map. The cache is consulted by the executor's
// compactionThresholdForModel via the cache-aware
// MaxContextTokensWithCache helper.
//
// Periodic refresh: a daily ticker re-runs RefreshAll so newly
// released models surface without a mort restart. The interval is
// intentionally not configurable — cloud model context lengths don't
// change for a given tag (only the tag pointer can move, e.g. :cloud
// → larger model), so daily is conservative.

package model

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"strings"
	"sync"
	"time"
)

// defaultCloudEndpoint is the public Ollama Cloud base URL. Override
// in tests via NewCloudOllamaLimitCache's endpoint arg.
const defaultCloudEndpoint = "https://ollama.com"

// CloudOllamaLimitCache holds context-length values for Ollama Cloud
// models, populated dynamically via /api/tags + /api/show. Construct
// with NewCloudOllamaLimitCache. Safe for concurrent use.
//
// Empty when OLLAMA_API_KEY is unset — Refresh returns a clear error
// and the cache stays empty. Lookups return (0, false) and callers
// fall back to the static map / disabled compaction.
type CloudOllamaLimitCache struct {
	mu       sync.RWMutex
	limit    map[string]int
	negative map[string]time.Time // model → fetch-failure time (for TTL)

	endpoint   string
	apiKey     string
	httpClient *http.Client

	// refreshConcurrency caps the number of concurrent /api/show calls
	// during RefreshAll. Default 8 — enough to finish a ~50-model
	// catalog in well under a minute without hammering Cloud.
	refreshConcurrency int

	// negativeTTL is how long a /api/show miss is cached before we
	// retry. Prevents hammering Cloud on a typo or recently-removed
	// model. Default 10 minutes.
	negativeTTL time.Duration
}

// NewCloudOllamaLimitCache constructs a fresh cache. apiKey can be
// empty — RefreshAll then returns an error and the cache stays empty.
// endpoint defaults to https://ollama.com when empty. httpClient
// defaults to a 15s-timeout client.
func NewCloudOllamaLimitCache(endpoint, apiKey string, httpClient *http.Client) *CloudOllamaLimitCache {
	if strings.TrimSpace(endpoint) == "" {
		endpoint = defaultCloudEndpoint
	}
	endpoint = strings.TrimRight(endpoint, "/")
	if httpClient == nil {
		httpClient = &http.Client{Timeout: 15 * time.Second}
	}
	return &CloudOllamaLimitCache{
		limit:              make(map[string]int),
		negative:           make(map[string]time.Time),
		endpoint:           endpoint,
		apiKey:             apiKey,
		httpClient:         httpClient,
		refreshConcurrency: 8,
		negativeTTL:        10 * time.Minute,
	}
}

// SetNegativeTTL overrides the negative-cache lifetime. Tests use this
// to control retry behaviour without sleeping.
func (c *CloudOllamaLimitCache) SetNegativeTTL(d time.Duration) {
	if c == nil || d < 0 {
		return
	}
	c.mu.Lock()
	c.negativeTTL = d
	c.mu.Unlock()
}

// Lookup returns the cached context length for an Ollama Cloud model
// name (e.g. "qwen3.5:cloud", "qwen3-coder:480b"). Returns (0, false)
// on miss. Lookup never makes HTTP calls — it's the hot path consulted
// by the executor before every run.
//
// modelName accepts either the bare model:tag form or the prefixed
// "ollama-cloud/model:tag" form; the prefix is stripped.
func (c *CloudOllamaLimitCache) Lookup(modelName string) (int, bool) {
	if c == nil {
		return 0, false
	}
	key := stripCloudPrefix(modelName)
	if key == "" {
		return 0, false
	}
	c.mu.RLock()
	defer c.mu.RUnlock()
	v, ok := c.limit[key]
	return v, ok
}

// Size returns the number of cached entries. Useful for logging /
// health checks.
func (c *CloudOllamaLimitCache) Size() int {
	if c == nil {
		return 0
	}
	c.mu.RLock()
	defer c.mu.RUnlock()
	return len(c.limit)
}

// LookupOrFetch returns the cached context length OR, on miss, makes a
// single /api/show call to populate the cache. Negative results
// (model not found, /api/show returns no context_length) are cached
// for negativeTTL to prevent hammering Cloud on a typo. Returns
// (0, false) when the model is genuinely unknown and (size, true) on
// any successful resolve.
//
// Why this exists: Ollama Cloud's /api/tags lists canonical model
// names only (e.g. "qwen3.5:397b") but accepts aliases on /api/show
// (e.g. "qwen3.5:cloud" → same 397b model). The boot-time RefreshAll
// only sees the canonical names, so common aliases miss the cache.
// LookupOrFetch fills the gap.
//
// The cache is therefore self-healing: any unknown model gets one
// live /api/show call, the result lands in the cache, and subsequent
// runs hit immediately. Periodic RefreshAll overwrites everything
// with the canonical-name results but additionally-fetched aliases
// linger as positive entries.
func (c *CloudOllamaLimitCache) LookupOrFetch(ctx context.Context, modelName string) (int, bool) {
	if c == nil {
		return 0, false
	}
	key := stripCloudPrefix(modelName)
	if key == "" {
		return 0, false
	}
	// Fast path: positive hit.
	c.mu.RLock()
	if v, ok := c.limit[key]; ok {
		c.mu.RUnlock()
		return v, true
	}
	// Negative cache check.
	if t, ok := c.negative[key]; ok && time.Since(t) < c.negativeTTL {
		c.mu.RUnlock()
		return 0, false
	}
	c.mu.RUnlock()
	// No API key configured → can't fetch. Don't write a negative
	// entry (when the key gets configured later we want the next call
	// to re-try immediately).
	if strings.TrimSpace(c.apiKey) == "" {
		return 0, false
	}
	// Slow path: live /api/show.
	n, err := c.fetchContextLength(ctx, key)
	if err != nil || n <= 0 {
		slog.Debug("cloud limit cache: lazy fetch miss",
			"model", key, "err", err)
		c.mu.Lock()
		c.negative[key] = time.Now()
		c.mu.Unlock()
		return 0, false
	}
	c.set(key, n)
	slog.Info("cloud limit cache: lazy fetch hit", "model", key, "context_length", n)
	return n, true
}

// set stores a context length. n <= 0 is a no-op.
func (c *CloudOllamaLimitCache) set(modelName string, n int) {
	if c == nil || n <= 0 {
		return
	}
	key := stripCloudPrefix(modelName)
	if key == "" {
		return
	}
	c.mu.Lock()
	c.limit[key] = n
	c.mu.Unlock()
}

// RefreshAll queries /api/tags then concurrently calls /api/show for
// every listed model, populating the cache. Returns the number of
// models successfully cached and the first error encountered (a
// /api/tags failure aborts; individual /api/show failures are logged
// but don't abort the whole refresh).
//
// Safe to call repeatedly. Cache entries are overwritten with the
// fresh values; entries for models that have been removed from Cloud
// are NOT pruned (cheap to keep; pruning risks dropping an entry just
// before a run that needs it).
func (c *CloudOllamaLimitCache) RefreshAll(ctx context.Context) (int, error) {
	if c == nil {
		return 0, fmt.Errorf("cloud limit cache: nil receiver")
	}
	if strings.TrimSpace(c.apiKey) == "" {
		return 0, fmt.Errorf("cloud limit cache: OLLAMA_API_KEY unset")
	}
	tags, err := c.fetchTags(ctx)
	if err != nil {
		return 0, fmt.Errorf("cloud limit cache: /api/tags: %w", err)
	}

	concurrency := c.refreshConcurrency
	if concurrency <= 0 {
		concurrency = 8
	}
	sem := make(chan struct{}, concurrency)
	var wg sync.WaitGroup
	var (
		mu      sync.Mutex
		success int
	)
	for _, name := range tags {
		name := name
		wg.Add(1)
		sem <- struct{}{}
		go func() {
			defer wg.Done()
			defer func() { <-sem }()
			ctxLen, ferr := c.fetchContextLength(ctx, name)
			if ferr != nil {
				slog.Debug("cloud limit cache: /api/show miss",
					"model", name, "err", ferr)
				return
			}
			c.set(name, ctxLen)
			mu.Lock()
			success++
			mu.Unlock()
		}()
	}
	wg.Wait()
	slog.Info("cloud limit cache: refresh complete",
		"models_total", len(tags), "cached", success)
	return success, nil
}

// StartPeriodicRefresh runs RefreshAll once immediately, then on every
// interval tick. Cancellation via ctx stops the loop. Logs each
// outcome; never returns an error to the caller (this is a background
// task — failures are warnings, not show-stoppers).
//
// Typical usage: a goroutine spawned at mort boot.
//
//	go cache.StartPeriodicRefresh(ctx, 24*time.Hour)
func (c *CloudOllamaLimitCache) StartPeriodicRefresh(ctx context.Context, interval time.Duration) {
	if c == nil {
		return
	}
	if interval <= 0 {
		interval = 24 * time.Hour
	}
	doOne := func() {
		n, err := c.RefreshAll(ctx)
		if err != nil {
			slog.Warn("cloud limit cache: refresh failed",
				"err", err, "cached_size", c.Size())
			return
		}
		slog.Info("cloud limit cache: refreshed",
			"newly_cached_or_updated", n, "cached_size", c.Size())
	}
	doOne()
	t := time.NewTicker(interval)
	defer t.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-t.C:
			doOne()
		}
	}
}

// fetchTags calls GET /api/tags and returns the model names.
func (c *CloudOllamaLimitCache) fetchTags(ctx context.Context) ([]string, error) {
	url := c.endpoint + "/api/tags"
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
	if err != nil {
		return nil, err
	}
	c.applyAuth(req)
	resp, err := c.httpClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	body, err := io.ReadAll(io.LimitReader(resp.Body, maxLimitCacheResponseBytes))
	if err != nil {
		return nil, err
	}
	if resp.StatusCode/100 != 2 {
		return nil, fmt.Errorf("status %d: %s", resp.StatusCode, truncate(body, 400))
	}
	var parsed struct {
		Models []struct {
			Name  string `json:"name"`
			Model string `json:"model"`
		} `json:"models"`
	}
	if err := json.Unmarshal(body, &parsed); err != nil {
		return nil, fmt.Errorf("parse /api/tags: %w", err)
	}
	out := make([]string, 0, len(parsed.Models))
	for _, m := range parsed.Models {
		name := m.Name
		if name == "" {
			name = m.Model
		}
		if name == "" {
			continue
		}
		out = append(out, name)
	}
	return out, nil
}

// fetchContextLength calls POST /api/show for a model and extracts
// the largest *.context_length value from model_info. Returns the
// length and nil on success; (0, err) on any failure.
//
// Why "largest" rather than family-keyed: the family field in the
// /api/show response is sometimes empty or doesn't match the
// model_info key prefix exactly (Ollama Cloud returns the
// architecture as the prefix, which usually but not always matches
// `family`). Scanning for any `*.context_length` is robust.
func (c *CloudOllamaLimitCache) fetchContextLength(ctx context.Context, modelName string) (int, error) {
	url := c.endpoint + "/api/show"
	body, _ := json.Marshal(map[string]string{"name": modelName})
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
	if err != nil {
		return 0, err
	}
	req.Header.Set("Content-Type", "application/json")
	c.applyAuth(req)
	resp, err := c.httpClient.Do(req)
	if err != nil {
		return 0, err
	}
	defer resp.Body.Close()
	respBody, err := io.ReadAll(io.LimitReader(resp.Body, maxLimitCacheResponseBytes))
	if err != nil {
		return 0, err
	}
	if resp.StatusCode/100 != 2 {
		return 0, fmt.Errorf("status %d: %s", resp.StatusCode, truncate(respBody, 400))
	}
	n, err := parseContextLengthJSON(respBody)
	if err != nil {
		return 0, err
	}
	return n, nil
}

// parseContextLengthJSON extracts the largest `*.context_length` int
// from an /api/show response body. Exported-ish (lowercase but tested
// in the same package) so the unit test can exercise it without
// spinning up an httptest server.
func parseContextLengthJSON(body []byte) (int, error) {
	var parsed struct {
		ModelInfo map[string]any `json:"model_info"`
	}
	if err := json.Unmarshal(body, &parsed); err != nil {
		return 0, fmt.Errorf("parse: %w", err)
	}
	best := 0
	for k, v := range parsed.ModelInfo {
		if !strings.HasSuffix(k, ".context_length") {
			continue
		}
		n := toInt(v)
		if n > best {
			best = n
		}
	}
	if best <= 0 {
		return 0, fmt.Errorf("no context_length in model_info")
	}
	return best, nil
}

// toInt coerces a JSON-decoded value to int. Handles float64 (the
// json default) and json.Number; returns 0 for anything else.
func toInt(v any) int {
	switch x := v.(type) {
	case float64:
		return int(x)
	case int:
		return x
	case int64:
		return int(x)
	case json.Number:
		if n, err := x.Int64(); err == nil {
			return int(n)
		}
	}
	return 0
}

// applyAuth sets the Bearer token when an API key is configured.
func (c *CloudOllamaLimitCache) applyAuth(req *http.Request) {
	if strings.TrimSpace(c.apiKey) == "" {
		return
	}
	req.Header.Set("Authorization", "Bearer "+strings.TrimSpace(c.apiKey))
}

// stripCloudPrefix strips an "ollama-cloud/" prefix (and surrounding
// whitespace). Returns the bare model:tag form.
func stripCloudPrefix(s string) string {
	s = strings.TrimSpace(s)
	if strings.HasPrefix(s, "ollama-cloud/") {
		s = s[len("ollama-cloud/"):]
	}
	return s
}

// truncate caps a byte slice for error messages.
func truncate(b []byte, n int) string {
	if len(b) <= n {
		return string(b)
	}
	return string(b[:n]) + "...(truncated)"
}

// maxLimitCacheResponseBytes bounds the ollama.com limit-cache HTTP responses
// (/api/tags, /api/show) so a misbehaving endpoint can't stream an unbounded
// body before the 15s timeout fires. 1 MiB is far above any real response.
const maxLimitCacheResponseBytes = 1 << 20