package core

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

const (
	defaultPresetsURL          = "https://raw.githubusercontent.com/chenhg5/cc-connect/main/provider-presets.json"
	fallbackPresetsURL         = "https://gitee.com/chenhg5/cc-connect/raw/main/provider-presets.json"
	presetsCacheTTL            = 6 * time.Hour
	presetsHTTPTimeout         = 15 * time.Second
	presetsFallbackHTTPTimeout = 10 * time.Second
)

// ProviderPreset describes a recommended provider available from the remote presets list.
type ProviderPreset struct {
	Name          string                       `json:"name"`
	DisplayName   string                       `json:"display_name"`
	Agents        map[string]PresetAgentConfig `json:"agents"` // per-agent-type configuration (keys: "claudecode", "codex", "gemini", "opencode", ...)
	InviteURL     string                       `json:"invite_url,omitempty"`
	Description   string                       `json:"description,omitempty"`
	DescriptionZh string                       `json:"description_zh,omitempty"`
	Features      []string                     `json:"features,omitempty"`
	Thinking      string                       `json:"thinking,omitempty"`
	Tier          int                          `json:"tier"`
	Featured      bool                         `json:"featured,omitempty"`
	Website       string                       `json:"website,omitempty"`
}

// PresetAgentConfig holds per-agent-type settings within a provider preset.
type PresetAgentConfig struct {
	BaseURL     string             `json:"base_url"`
	Model       string             `json:"model"`
	Models      []string           `json:"models,omitempty"`
	CodexConfig *PresetCodexConfig `json:"codex_config,omitempty"`
}

// PresetCodexConfig holds Codex-specific provider settings that get written
// to Codex's config.toml as [model_providers.<name>].
type PresetCodexConfig struct {
	EnvKey      string            `json:"env_key,omitempty"`
	WireAPI     string            `json:"wire_api,omitempty"`
	HTTPHeaders map[string]string `json:"http_headers,omitempty"`
}

// SupportsAgent returns true if the preset supports the given agent type.
func (p *ProviderPreset) SupportsAgent(agentType string) bool {
	_, ok := p.Agents[agentType]
	return ok
}

// AgentConfig returns the agent-specific config, or nil if unsupported.
func (p *ProviderPreset) AgentConfig(agentType string) *PresetAgentConfig {
	ac, ok := p.Agents[agentType]
	if !ok {
		return nil
	}
	return &ac
}

// ProviderPresetsResponse is the top-level JSON schema for remote presets.
type ProviderPresetsResponse struct {
	Version   int              `json:"version"`
	UpdatedAt string           `json:"updated_at,omitempty"`
	Providers []ProviderPreset `json:"providers"`
}

type presetsCache struct {
	mu        sync.RWMutex
	data      *ProviderPresetsResponse
	fetchedAt time.Time
	url       string
}

var globalPresetsCache = &presetsCache{}

// SetPresetsURL overrides the default presets URL. Call before first fetch.
func SetPresetsURL(url string) {
	globalPresetsCache.mu.Lock()
	defer globalPresetsCache.mu.Unlock()
	globalPresetsCache.url = url
	globalPresetsCache.data = nil // invalidate cache on URL change
}

// FetchProviderPresets returns cached or freshly-fetched provider presets.
func FetchProviderPresets() (*ProviderPresetsResponse, error) {
	return globalPresetsCache.fetch()
}

func (c *presetsCache) fetch() (*ProviderPresetsResponse, error) {
	c.mu.RLock()
	if c.data != nil && time.Since(c.fetchedAt) < presetsCacheTTL {
		defer c.mu.RUnlock()
		return c.data, nil
	}
	c.mu.RUnlock()

	c.mu.Lock()
	defer c.mu.Unlock()

	// double-check after acquiring write lock
	if c.data != nil && time.Since(c.fetchedAt) < presetsCacheTTL {
		return c.data, nil
	}

	primaryURL := c.url
	if primaryURL == "" {
		primaryURL = defaultPresetsURL
	}

	result, err := fetchPresetsFromURL(primaryURL, presetsHTTPTimeout)
	if err != nil {
		slog.Warn("primary presets fetch failed, trying fallback", "url", primaryURL, "error", err)
		result, err = fetchPresetsFromURL(fallbackPresetsURL, presetsFallbackHTTPTimeout)
	}
	if err != nil {
		if c.data != nil {
			slog.Warn("all presets sources failed, using stale cache", "error", err)
			return c.data, nil
		}
		return nil, fmt.Errorf("fetch presets: %w", err)
	}

	c.data = result
	c.fetchedAt = time.Now()
	return c.data, nil
}

func fetchPresetsFromURL(url string, timeout time.Duration) (*ProviderPresetsResponse, error) {
	slog.Debug("fetching provider presets", "url", url)
	client := &http.Client{Timeout: timeout}
	resp, err := client.Get(url)
	if err != nil {
		return nil, fmt.Errorf("HTTP GET %s: %w", url, err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("HTTP GET %s: status %d", url, resp.StatusCode)
	}

	body, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
	if err != nil {
		return nil, fmt.Errorf("read body from %s: %w", url, err)
	}

	var result ProviderPresetsResponse
	if err := json.Unmarshal(body, &result); err != nil {
		return nil, fmt.Errorf("parse JSON from %s: %w", url, err)
	}
	return &result, nil
}