package executor

import (
	"bytes"
	"context"
	"fmt"
	"sync"
	"time"

	"github.com/gin-gonic/gin"
	cliproxyauth "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/auth"
	"github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/usage"
	"github.com/tidwall/gjson"
)

type usageReporter struct {
	provider    string
	model       string
	authID      string
	apiKey      string
	requestedAt time.Time
	once        sync.Once
}

func newUsageReporter(ctx context.Context, provider, model string, auth *cliproxyauth.Auth) *usageReporter {
	reporter := &usageReporter{
		provider:    provider,
		model:       model,
		requestedAt: time.Now(),
	}
	if auth != nil {
		reporter.authID = auth.ID
	}
	reporter.apiKey = apiKeyFromContext(ctx)
	return reporter
}

func (r *usageReporter) publish(ctx context.Context, detail usage.Detail) {
	if r == nil {
		return
	}
	if detail.TotalTokens == 0 {
		total := detail.InputTokens + detail.OutputTokens + detail.ReasoningTokens
		if total > 0 {
			detail.TotalTokens = total
		}
	}
	if detail.InputTokens == 0 && detail.OutputTokens == 0 && detail.ReasoningTokens == 0 && detail.CachedTokens == 0 && detail.TotalTokens == 0 {
		return
	}
	r.once.Do(func() {
		usage.PublishRecord(ctx, usage.Record{
			Provider:    r.provider,
			Model:       r.model,
			APIKey:      r.apiKey,
			AuthID:      r.authID,
			RequestedAt: r.requestedAt,
			Detail:      detail,
		})
	})
}

func apiKeyFromContext(ctx context.Context) string {
	if ctx == nil {
		return ""
	}
	ginCtx, ok := ctx.Value("gin").(*gin.Context)
	if !ok || ginCtx == nil {
		return ""
	}
	if v, exists := ginCtx.Get("apiKey"); exists {
		switch value := v.(type) {
		case string:
			return value
		case fmt.Stringer:
			return value.String()
		default:
			return fmt.Sprintf("%v", value)
		}
	}
	return ""
}

func parseCodexUsage(data []byte) (usage.Detail, bool) {
	usageNode := gjson.ParseBytes(data).Get("response.usage")
	if !usageNode.Exists() {
		return usage.Detail{}, false
	}
	detail := usage.Detail{
		InputTokens:  usageNode.Get("input_tokens").Int(),
		OutputTokens: usageNode.Get("output_tokens").Int(),
		TotalTokens:  usageNode.Get("total_tokens").Int(),
	}
	if cached := usageNode.Get("input_tokens_details.cached_tokens"); cached.Exists() {
		detail.CachedTokens = cached.Int()
	}
	if reasoning := usageNode.Get("output_tokens_details.reasoning_tokens"); reasoning.Exists() {
		detail.ReasoningTokens = reasoning.Int()
	}
	return detail, true
}

func parseOpenAIUsage(data []byte) usage.Detail {
	usageNode := gjson.ParseBytes(data).Get("usage")
	if !usageNode.Exists() {
		return usage.Detail{}
	}
	detail := usage.Detail{
		InputTokens:  usageNode.Get("prompt_tokens").Int(),
		OutputTokens: usageNode.Get("completion_tokens").Int(),
		TotalTokens:  usageNode.Get("total_tokens").Int(),
	}
	if cached := usageNode.Get("prompt_tokens_details.cached_tokens"); cached.Exists() {
		detail.CachedTokens = cached.Int()
	}
	if reasoning := usageNode.Get("completion_tokens_details.reasoning_tokens"); reasoning.Exists() {
		detail.ReasoningTokens = reasoning.Int()
	}
	return detail
}

func parseOpenAIStreamUsage(line []byte) (usage.Detail, bool) {
	payload := jsonPayload(line)
	if len(payload) == 0 || !gjson.ValidBytes(payload) {
		return usage.Detail{}, false
	}
	usageNode := gjson.GetBytes(payload, "usage")
	if !usageNode.Exists() {
		return usage.Detail{}, false
	}
	detail := usage.Detail{
		InputTokens:  usageNode.Get("prompt_tokens").Int(),
		OutputTokens: usageNode.Get("completion_tokens").Int(),
		TotalTokens:  usageNode.Get("total_tokens").Int(),
	}
	if cached := usageNode.Get("prompt_tokens_details.cached_tokens"); cached.Exists() {
		detail.CachedTokens = cached.Int()
	}
	if reasoning := usageNode.Get("completion_tokens_details.reasoning_tokens"); reasoning.Exists() {
		detail.ReasoningTokens = reasoning.Int()
	}
	return detail, true
}

func parseClaudeUsage(data []byte) usage.Detail {
	usageNode := gjson.ParseBytes(data).Get("usage")
	if !usageNode.Exists() {
		return usage.Detail{}
	}
	detail := usage.Detail{
		InputTokens:  usageNode.Get("input_tokens").Int(),
		OutputTokens: usageNode.Get("output_tokens").Int(),
		CachedTokens: usageNode.Get("cache_read_input_tokens").Int(),
	}
	if detail.CachedTokens == 0 {
		// fall back to creation tokens when read tokens are absent
		detail.CachedTokens = usageNode.Get("cache_creation_input_tokens").Int()
	}
	detail.TotalTokens = detail.InputTokens + detail.OutputTokens
	return detail
}

func parseClaudeStreamUsage(line []byte) (usage.Detail, bool) {
	payload := jsonPayload(line)
	if len(payload) == 0 || !gjson.ValidBytes(payload) {
		return usage.Detail{}, false
	}
	usageNode := gjson.GetBytes(payload, "usage")
	if !usageNode.Exists() {
		return usage.Detail{}, false
	}
	detail := usage.Detail{
		InputTokens:  usageNode.Get("input_tokens").Int(),
		OutputTokens: usageNode.Get("output_tokens").Int(),
		CachedTokens: usageNode.Get("cache_read_input_tokens").Int(),
	}
	if detail.CachedTokens == 0 {
		detail.CachedTokens = usageNode.Get("cache_creation_input_tokens").Int()
	}
	detail.TotalTokens = detail.InputTokens + detail.OutputTokens
	return detail, true
}

func parseGeminiCLIUsage(data []byte) usage.Detail {
	usageNode := gjson.ParseBytes(data)
	node := usageNode.Get("response.usageMetadata")
	if !node.Exists() {
		node = usageNode.Get("response.usage_metadata")
	}
	if !node.Exists() {
		return usage.Detail{}
	}
	detail := usage.Detail{
		InputTokens:     node.Get("promptTokenCount").Int(),
		OutputTokens:    node.Get("candidatesTokenCount").Int(),
		ReasoningTokens: node.Get("thoughtsTokenCount").Int(),
		TotalTokens:     node.Get("totalTokenCount").Int(),
	}
	if detail.TotalTokens == 0 {
		detail.TotalTokens = detail.InputTokens + detail.OutputTokens + detail.ReasoningTokens
	}
	return detail
}

func parseGeminiUsage(data []byte) usage.Detail {
	usageNode := gjson.ParseBytes(data)
	node := usageNode.Get("usageMetadata")
	if !node.Exists() {
		node = usageNode.Get("usage_metadata")
	}
	if !node.Exists() {
		return usage.Detail{}
	}
	detail := usage.Detail{
		InputTokens:     node.Get("promptTokenCount").Int(),
		OutputTokens:    node.Get("candidatesTokenCount").Int(),
		ReasoningTokens: node.Get("thoughtsTokenCount").Int(),
		TotalTokens:     node.Get("totalTokenCount").Int(),
	}
	if detail.TotalTokens == 0 {
		detail.TotalTokens = detail.InputTokens + detail.OutputTokens + detail.ReasoningTokens
	}
	return detail
}

func parseGeminiStreamUsage(line []byte) (usage.Detail, bool) {
	payload := jsonPayload(line)
	if len(payload) == 0 || !gjson.ValidBytes(payload) {
		return usage.Detail{}, false
	}
	node := gjson.GetBytes(payload, "usageMetadata")
	if !node.Exists() {
		node = gjson.GetBytes(payload, "usage_metadata")
	}
	if !node.Exists() {
		return usage.Detail{}, false
	}
	detail := usage.Detail{
		InputTokens:     node.Get("promptTokenCount").Int(),
		OutputTokens:    node.Get("candidatesTokenCount").Int(),
		ReasoningTokens: node.Get("thoughtsTokenCount").Int(),
		TotalTokens:     node.Get("totalTokenCount").Int(),
	}
	if detail.TotalTokens == 0 {
		detail.TotalTokens = detail.InputTokens + detail.OutputTokens + detail.ReasoningTokens
	}
	return detail, true
}

func parseGeminiCLIStreamUsage(line []byte) (usage.Detail, bool) {
	payload := jsonPayload(line)
	if len(payload) == 0 || !gjson.ValidBytes(payload) {
		return usage.Detail{}, false
	}
	node := gjson.GetBytes(payload, "response.usageMetadata")
	if !node.Exists() {
		node = gjson.GetBytes(payload, "usage_metadata")
	}
	if !node.Exists() {
		return usage.Detail{}, false
	}
	detail := usage.Detail{
		InputTokens:     node.Get("promptTokenCount").Int(),
		OutputTokens:    node.Get("candidatesTokenCount").Int(),
		ReasoningTokens: node.Get("thoughtsTokenCount").Int(),
		TotalTokens:     node.Get("totalTokenCount").Int(),
	}
	if detail.TotalTokens == 0 {
		detail.TotalTokens = detail.InputTokens + detail.OutputTokens + detail.ReasoningTokens
	}
	return detail, true
}

func jsonPayload(line []byte) []byte {
	trimmed := bytes.TrimSpace(line)
	if len(trimmed) == 0 {
		return nil
	}
	if bytes.Equal(trimmed, []byte("[DONE]")) {
		return nil
	}
	if bytes.HasPrefix(trimmed, []byte("event:")) {
		return nil
	}
	if bytes.HasPrefix(trimmed, []byte("data:")) {
		trimmed = bytes.TrimSpace(trimmed[len("data:"):])
	}
	if len(trimmed) == 0 || trimmed[0] != '{' {
		return nil
	}
	return trimmed
}