package executor

import (
	"bufio"
	"bytes"
	"context"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"

	"github.com/router-for-me/CLIProxyAPI/v6/internal/config"
	"github.com/router-for-me/CLIProxyAPI/v6/internal/util"
	cliproxyauth "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/auth"
	cliproxyexecutor "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/executor"
	sdktranslator "github.com/router-for-me/CLIProxyAPI/v6/sdk/translator"
	log "github.com/sirupsen/logrus"
	"github.com/tidwall/sjson"
)

// OpenAICompatExecutor implements a stateless executor for OpenAI-compatible providers.
// It performs request/response translation and executes against the provider base URL
// using per-auth credentials (API key) and per-auth HTTP transport (proxy) from context.
type OpenAICompatExecutor struct {
	provider string
	cfg      *config.Config
}

// NewOpenAICompatExecutor creates an executor bound to a provider key (e.g., "openrouter").
func NewOpenAICompatExecutor(provider string, cfg *config.Config) *OpenAICompatExecutor {
	return &OpenAICompatExecutor{provider: provider, cfg: cfg}
}

// Identifier implements cliproxyauth.ProviderExecutor.
func (e *OpenAICompatExecutor) Identifier() string { return e.provider }

// PrepareRequest is a no-op for now (credentials are added via headers at execution time).
func (e *OpenAICompatExecutor) PrepareRequest(_ *http.Request, _ *cliproxyauth.Auth) error {
	return nil
}

func (e *OpenAICompatExecutor) Execute(ctx context.Context, auth *cliproxyauth.Auth, req cliproxyexecutor.Request, opts cliproxyexecutor.Options) (resp cliproxyexecutor.Response, err error) {
	reporter := newUsageReporter(ctx, e.Identifier(), req.Model, auth)
	defer reporter.trackFailure(ctx, &err)

	baseURL, apiKey := e.resolveCredentials(auth)
	if baseURL == "" {
		err = statusErr{code: http.StatusUnauthorized, msg: "missing provider baseURL"}
		return
	}

	// Translate inbound request to OpenAI format
	from := opts.SourceFormat
	to := sdktranslator.FromString("openai")
	originalPayload := bytes.Clone(req.Payload)
	if len(opts.OriginalRequest) > 0 {
		originalPayload = bytes.Clone(opts.OriginalRequest)
	}
	originalTranslated := sdktranslator.TranslateRequest(from, to, req.Model, originalPayload, opts.Stream)
	translated := sdktranslator.TranslateRequest(from, to, req.Model, bytes.Clone(req.Payload), opts.Stream)
	modelOverride := e.resolveUpstreamModel(req.Model, auth)
	if modelOverride != "" {
		translated = e.overrideModel(translated, modelOverride)
	}
	translated = applyPayloadConfigWithRoot(e.cfg, req.Model, to.String(), "", translated, originalTranslated)
	allowCompat := e.allowCompatReasoningEffort(req.Model, auth)
	translated = ApplyReasoningEffortMetadata(translated, req.Metadata, req.Model, "reasoning_effort", allowCompat)
	translated = NormalizeThinkingConfig(translated, req.Model, allowCompat)
	if errValidate := ValidateThinkingConfig(translated, req.Model); errValidate != nil {
		return resp, errValidate
	}

	url := strings.TrimSuffix(baseURL, "/") + "/chat/completions"
	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(translated))
	if err != nil {
		return resp, err
	}
	httpReq.Header.Set("Content-Type", "application/json")
	if apiKey != "" {
		httpReq.Header.Set("Authorization", "Bearer "+apiKey)
	}
	httpReq.Header.Set("User-Agent", "cli-proxy-openai-compat")
	var attrs map[string]string
	if auth != nil {
		attrs = auth.Attributes
	}
	util.ApplyCustomHeadersFromAttrs(httpReq, attrs)
	var authID, authLabel, authType, authValue string
	if auth != nil {
		authID = auth.ID
		authLabel = auth.Label
		authType, authValue = auth.AccountInfo()
	}
	recordAPIRequest(ctx, e.cfg, upstreamRequestLog{
		URL:       url,
		Method:    http.MethodPost,
		Headers:   httpReq.Header.Clone(),
		Body:      translated,
		Provider:  e.Identifier(),
		AuthID:    authID,
		AuthLabel: authLabel,
		AuthType:  authType,
		AuthValue: authValue,
	})

	httpClient := newProxyAwareHTTPClient(ctx, e.cfg, auth, 0)
	httpResp, err := httpClient.Do(httpReq)
	if err != nil {
		recordAPIResponseError(ctx, e.cfg, err)
		return resp, err
	}
	defer func() {
		if errClose := httpResp.Body.Close(); errClose != nil {
			log.Errorf("openai compat executor: close response body error: %v", errClose)
		}
	}()
	recordAPIResponseMetadata(ctx, e.cfg, httpResp.StatusCode, httpResp.Header.Clone())
	if httpResp.StatusCode < 200 || httpResp.StatusCode >= 300 {
		b, _ := io.ReadAll(httpResp.Body)
		appendAPIResponseChunk(ctx, e.cfg, b)
		log.Warnf("openai-compat executor: upstream API error, status: %d, body: %s", httpResp.StatusCode, summarizeErrorBody(httpResp.Header.Get("Content-Type"), b))
		err = statusErr{code: httpResp.StatusCode, msg: string(b)}
		return resp, err
	}
	body, err := io.ReadAll(httpResp.Body)
	if err != nil {
		recordAPIResponseError(ctx, e.cfg, err)
		return resp, err
	}
	appendAPIResponseChunk(ctx, e.cfg, body)
	reporter.publish(ctx, parseOpenAIUsage(body))
	// Ensure we at least record the request even if upstream doesn't return usage
	reporter.ensurePublished(ctx)
	// Translate response back to source format when needed
	var param any
	out := sdktranslator.TranslateNonStream(ctx, to, from, req.Model, bytes.Clone(opts.OriginalRequest), translated, body, &param)
	resp = cliproxyexecutor.Response{Payload: []byte(out)}
	return resp, nil
}

func (e *OpenAICompatExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.Auth, req cliproxyexecutor.Request, opts cliproxyexecutor.Options) (stream <-chan cliproxyexecutor.StreamChunk, err error) {
	reporter := newUsageReporter(ctx, e.Identifier(), req.Model, auth)
	defer reporter.trackFailure(ctx, &err)

	baseURL, apiKey := e.resolveCredentials(auth)
	if baseURL == "" {
		err = statusErr{code: http.StatusUnauthorized, msg: "missing provider baseURL"}
		return nil, err
	}
	from := opts.SourceFormat
	to := sdktranslator.FromString("openai")
	originalPayload := bytes.Clone(req.Payload)
	if len(opts.OriginalRequest) > 0 {
		originalPayload = bytes.Clone(opts.OriginalRequest)
	}
	originalTranslated := sdktranslator.TranslateRequest(from, to, req.Model, originalPayload, true)
	translated := sdktranslator.TranslateRequest(from, to, req.Model, bytes.Clone(req.Payload), true)
	modelOverride := e.resolveUpstreamModel(req.Model, auth)
	if modelOverride != "" {
		translated = e.overrideModel(translated, modelOverride)
	}
	translated = applyPayloadConfigWithRoot(e.cfg, req.Model, to.String(), "", translated, originalTranslated)
	allowCompat := e.allowCompatReasoningEffort(req.Model, auth)
	translated = ApplyReasoningEffortMetadata(translated, req.Metadata, req.Model, "reasoning_effort", allowCompat)
	translated = NormalizeThinkingConfig(translated, req.Model, allowCompat)
	if errValidate := ValidateThinkingConfig(translated, req.Model); errValidate != nil {
		return nil, errValidate
	}

	url := strings.TrimSuffix(baseURL, "/") + "/chat/completions"
	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(translated))
	if err != nil {
		return nil, err
	}
	httpReq.Header.Set("Content-Type", "application/json")
	if apiKey != "" {
		httpReq.Header.Set("Authorization", "Bearer "+apiKey)
	}
	httpReq.Header.Set("User-Agent", "cli-proxy-openai-compat")
	var attrs map[string]string
	if auth != nil {
		attrs = auth.Attributes
	}
	util.ApplyCustomHeadersFromAttrs(httpReq, attrs)
	httpReq.Header.Set("Accept", "text/event-stream")
	httpReq.Header.Set("Cache-Control", "no-cache")
	var authID, authLabel, authType, authValue string
	if auth != nil {
		authID = auth.ID
		authLabel = auth.Label
		authType, authValue = auth.AccountInfo()
	}
	recordAPIRequest(ctx, e.cfg, upstreamRequestLog{
		URL:       url,
		Method:    http.MethodPost,
		Headers:   httpReq.Header.Clone(),
		Body:      translated,
		Provider:  e.Identifier(),
		AuthID:    authID,
		AuthLabel: authLabel,
		AuthType:  authType,
		AuthValue: authValue,
	})

	httpClient := newProxyAwareHTTPClient(ctx, e.cfg, auth, 0)
	httpResp, err := httpClient.Do(httpReq)
	if err != nil {
		recordAPIResponseError(ctx, e.cfg, err)
		return nil, err
	}
	recordAPIResponseMetadata(ctx, e.cfg, httpResp.StatusCode, httpResp.Header.Clone())
	if httpResp.StatusCode < 200 || httpResp.StatusCode >= 300 {
		b, _ := io.ReadAll(httpResp.Body)
		appendAPIResponseChunk(ctx, e.cfg, b)
		log.Warnf("openai-compat executor: upstream API error, status: %d, body: %s", httpResp.StatusCode, summarizeErrorBody(httpResp.Header.Get("Content-Type"), b))
		if errClose := httpResp.Body.Close(); errClose != nil {
			log.Errorf("openai compat executor: close response body error: %v", errClose)
		}
		err = statusErr{code: httpResp.StatusCode, msg: string(b)}
		return nil, err
	}
	out := make(chan cliproxyexecutor.StreamChunk)
	stream = out
	go func() {
		defer close(out)
		defer func() {
			if errClose := httpResp.Body.Close(); errClose != nil {
				log.Errorf("openai compat executor: close response body error: %v", errClose)
			}
		}()
		scanner := bufio.NewScanner(httpResp.Body)
		scanner.Buffer(nil, 52_428_800) // 50MB
		var param any
		for scanner.Scan() {
			line := scanner.Bytes()
			appendAPIResponseChunk(ctx, e.cfg, line)
			if detail, ok := parseOpenAIStreamUsage(line); ok {
				reporter.publish(ctx, detail)
			}
			if len(line) == 0 {
				continue
			}
			// OpenAI-compatible streams are SSE: lines typically prefixed with "data: ".
			// Pass through translator; it yields one or more chunks for the target schema.
			chunks := sdktranslator.TranslateStream(ctx, to, from, req.Model, bytes.Clone(opts.OriginalRequest), translated, bytes.Clone(line), &param)
			for i := range chunks {
				out <- cliproxyexecutor.StreamChunk{Payload: []byte(chunks[i])}
			}
		}
		if errScan := scanner.Err(); errScan != nil {
			recordAPIResponseError(ctx, e.cfg, errScan)
			reporter.publishFailure(ctx)
			out <- cliproxyexecutor.StreamChunk{Err: errScan}
		}
		// Ensure we record the request if no usage chunk was ever seen
		reporter.ensurePublished(ctx)
	}()
	return stream, nil
}

func (e *OpenAICompatExecutor) CountTokens(ctx context.Context, auth *cliproxyauth.Auth, req cliproxyexecutor.Request, opts cliproxyexecutor.Options) (cliproxyexecutor.Response, error) {
	from := opts.SourceFormat
	to := sdktranslator.FromString("openai")
	translated := sdktranslator.TranslateRequest(from, to, req.Model, bytes.Clone(req.Payload), false)

	modelForCounting := req.Model
	if modelOverride := e.resolveUpstreamModel(req.Model, auth); modelOverride != "" {
		translated = e.overrideModel(translated, modelOverride)
		modelForCounting = modelOverride
	}

	enc, err := tokenizerForModel(modelForCounting)
	if err != nil {
		return cliproxyexecutor.Response{}, fmt.Errorf("openai compat executor: tokenizer init failed: %w", err)
	}

	count, err := countOpenAIChatTokens(enc, translated)
	if err != nil {
		return cliproxyexecutor.Response{}, fmt.Errorf("openai compat executor: token counting failed: %w", err)
	}

	usageJSON := buildOpenAIUsageJSON(count)
	translatedUsage := sdktranslator.TranslateTokenCount(ctx, to, from, count, usageJSON)
	return cliproxyexecutor.Response{Payload: []byte(translatedUsage)}, nil
}

// Refresh is a no-op for API-key based compatibility providers.
func (e *OpenAICompatExecutor) Refresh(ctx context.Context, auth *cliproxyauth.Auth) (*cliproxyauth.Auth, error) {
	log.Debugf("openai compat executor: refresh called")
	_ = ctx
	return auth, nil
}

func (e *OpenAICompatExecutor) resolveCredentials(auth *cliproxyauth.Auth) (baseURL, apiKey string) {
	if auth == nil {
		return "", ""
	}
	if auth.Attributes != nil {
		baseURL = strings.TrimSpace(auth.Attributes["base_url"])
		apiKey = strings.TrimSpace(auth.Attributes["api_key"])
	}
	return
}

func (e *OpenAICompatExecutor) resolveUpstreamModel(alias string, auth *cliproxyauth.Auth) string {
	if alias == "" || auth == nil || e.cfg == nil {
		return ""
	}
	compat := e.resolveCompatConfig(auth)
	if compat == nil {
		return ""
	}
	for i := range compat.Models {
		model := compat.Models[i]
		if model.Alias != "" {
			if strings.EqualFold(model.Alias, alias) {
				if model.Name != "" {
					return model.Name
				}
				return alias
			}
			continue
		}
		if strings.EqualFold(model.Name, alias) {
			return model.Name
		}
	}
	return ""
}

func (e *OpenAICompatExecutor) allowCompatReasoningEffort(model string, auth *cliproxyauth.Auth) bool {
	trimmed := strings.TrimSpace(model)
	if trimmed == "" || e == nil || e.cfg == nil {
		return false
	}
	compat := e.resolveCompatConfig(auth)
	if compat == nil || len(compat.Models) == 0 {
		return false
	}
	for i := range compat.Models {
		entry := compat.Models[i]
		if strings.EqualFold(strings.TrimSpace(entry.Alias), trimmed) {
			return true
		}
		if strings.EqualFold(strings.TrimSpace(entry.Name), trimmed) {
			return true
		}
	}
	return false
}

func (e *OpenAICompatExecutor) resolveCompatConfig(auth *cliproxyauth.Auth) *config.OpenAICompatibility {
	if auth == nil || e.cfg == nil {
		return nil
	}
	candidates := make([]string, 0, 3)
	if auth.Attributes != nil {
		if v := strings.TrimSpace(auth.Attributes["compat_name"]); v != "" {
			candidates = append(candidates, v)
		}
		if v := strings.TrimSpace(auth.Attributes["provider_key"]); v != "" {
			candidates = append(candidates, v)
		}
	}
	if v := strings.TrimSpace(auth.Provider); v != "" {
		candidates = append(candidates, v)
	}
	for i := range e.cfg.OpenAICompatibility {
		compat := &e.cfg.OpenAICompatibility[i]
		for _, candidate := range candidates {
			if candidate != "" && strings.EqualFold(strings.TrimSpace(candidate), compat.Name) {
				return compat
			}
		}
	}
	return nil
}

func (e *OpenAICompatExecutor) overrideModel(payload []byte, model string) []byte {
	if len(payload) == 0 || model == "" {
		return payload
	}
	payload, _ = sjson.SetBytes(payload, "model", model)
	return payload
}

type statusErr struct {
	code       int
	msg        string
	retryAfter *time.Duration
}

func (e statusErr) Error() string {
	if e.msg != "" {
		return e.msg
	}
	return fmt.Sprintf("status %d", e.code)
}
func (e statusErr) StatusCode() int            { return e.code }
func (e statusErr) RetryAfter() *time.Duration { return e.retryAfter }