package embeddingprovider

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"math"
	"net/http"
	"net/url"
	"strings"
	"time"

	"data-terminal-cloud/internal/developmentembedding"
	"data-terminal-cloud/internal/outbox"
)

const Dimensions = developmentembedding.Dimensions

type Result struct {
	Vector      []float64
	ProviderRef string
}

type Provider interface {
	Embed(context.Context, string) (Result, error)
}

type Local struct{}

func (Local) Embed(_ context.Context, content string) (Result, error) {
	if strings.TrimSpace(content) == "" {
		return Result{}, errors.New("embedding content is required")
	}
	return Result{Vector: developmentembedding.Vector(content), ProviderRef: "local-deterministic-hash-v1"}, nil
}

type Ark struct {
	endpoint string
	apiKey   string
	model    string
	client   *http.Client
}

func NewArk(baseURL, apiKey, model string, timeout time.Duration) (*Ark, error) {
	baseURL = strings.TrimRight(strings.TrimSpace(baseURL), "/")
	apiKey = strings.TrimSpace(apiKey)
	model = strings.TrimSpace(model)
	parsed, err := url.Parse(baseURL)
	if err != nil || parsed.Host == "" || (parsed.Scheme != "http" && parsed.Scheme != "https") {
		return nil, errors.New("Ark base URL must be an absolute HTTP(S) URL")
	}
	if apiKey == "" || model == "" || timeout <= 0 {
		return nil, errors.New("Ark API key, embedding model and positive timeout are required")
	}
	return &Ark{endpoint: baseURL + "/embeddings", apiKey: apiKey, model: model, client: &http.Client{Timeout: timeout}}, nil
}

func (a *Ark) Embed(ctx context.Context, content string) (Result, error) {
	content = strings.TrimSpace(content)
	if content == "" {
		return Result{}, errors.New("embedding content is required")
	}
	body, err := json.Marshal(map[string]any{
		"model": a.model, "input": content, "encoding_format": "float", "dimensions": Dimensions,
	})
	if err != nil {
		return Result{}, err
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, a.endpoint, bytes.NewReader(body))
	if err != nil {
		return Result{}, fmt.Errorf("build Ark embedding request: %w", err)
	}
	req.Header.Set("Authorization", "Bearer "+a.apiKey)
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("User-Agent", "voice-platform-memory-embedding/1.0")
	resp, err := a.client.Do(req)
	if err != nil {
		return Result{}, outbox.Retryable(fmt.Errorf("call Ark embedding model: %w", err))
	}
	defer resp.Body.Close()
	responseBody, readErr := io.ReadAll(io.LimitReader(resp.Body, 4<<20))
	if readErr != nil {
		return Result{}, outbox.Retryable(fmt.Errorf("read Ark embedding response: %w", readErr))
	}
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		requestErr := fmt.Errorf("Ark embedding model returned HTTP %d", resp.StatusCode)
		if resp.StatusCode == http.StatusRequestTimeout || resp.StatusCode == http.StatusTooEarly || resp.StatusCode == http.StatusTooManyRequests || resp.StatusCode >= 500 {
			return Result{}, outbox.Retryable(requestErr)
		}
		return Result{}, requestErr
	}
	var response struct {
		Data []struct {
			Index     int       `json:"index"`
			Embedding []float64 `json:"embedding"`
		} `json:"data"`
	}
	if err = json.Unmarshal(responseBody, &response); err != nil || len(response.Data) != 1 || response.Data[0].Index != 0 {
		return Result{}, outbox.Retryable(errors.New("Ark embedding response has no usable vector"))
	}
	if err = Validate(response.Data[0].Embedding); err != nil {
		return Result{}, outbox.Retryable(err)
	}
	return Result{Vector: response.Data[0].Embedding, ProviderRef: "ark:" + a.model}, nil
}

func Validate(vector []float64) error {
	if len(vector) != Dimensions {
		return fmt.Errorf("embedding dimensions=%d want=%d", len(vector), Dimensions)
	}
	for _, value := range vector {
		if math.IsNaN(value) || math.IsInf(value, 0) {
			return errors.New("embedding contains a non-finite value")
		}
	}
	return nil
}

func Literal(vector []float64) (string, error) {
	if err := Validate(vector); err != nil {
		return "", err
	}
	return developmentembedding.Literal(vector), nil
}