package cli

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"mime/multipart"
	"net/http"
	"path/filepath"
	"strings"
	"time"
)

// APIClient is a REST client for the Multica server API.
// Used by ctrl subcommands (agent, runtime, status, etc.).
//
// TODO: Add Authorization header support. Agent routes (/api/agents/...)
// require JWT auth via middleware.Auth, but this client currently sends
// no auth token. CLI agent commands will fail with 401 until this is added.
type APIClient struct {
	BaseURL     string
	WorkspaceID string
	Token       string
	AgentID     string // When set, requests are attributed to this agent instead of the user.
	TaskID      string // When set, sent as X-Task-ID for agent-task validation.
	HTTPClient  *http.Client
}

// NewAPIClient creates a new API client for ctrl commands.
func NewAPIClient(baseURL, workspaceID, token string) *APIClient {
	return &APIClient{
		BaseURL:     strings.TrimRight(baseURL, "/"),
		WorkspaceID: workspaceID,
		Token:       token,
		HTTPClient:  &http.Client{Timeout: 15 * time.Second},
	}
}

func (c *APIClient) setHeaders(req *http.Request) {
	if c.Token != "" {
		req.Header.Set("Authorization", "Bearer "+c.Token)
	}
	if c.WorkspaceID != "" {
		req.Header.Set("X-Workspace-ID", c.WorkspaceID)
	}
	if c.AgentID != "" {
		req.Header.Set("X-Agent-ID", c.AgentID)
	}
	if c.TaskID != "" {
		req.Header.Set("X-Task-ID", c.TaskID)
	}
}

// GetJSON performs a GET request and decodes the JSON response.
func (c *APIClient) GetJSON(ctx context.Context, path string, out any) error {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, c.BaseURL+path, nil)
	if err != nil {
		return err
	}
	c.setHeaders(req)

	resp, err := c.HTTPClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 400 {
		data, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
		return fmt.Errorf("GET %s returned %d: %s", path, resp.StatusCode, strings.TrimSpace(string(data)))
	}
	if out == nil {
		return nil
	}
	return json.NewDecoder(resp.Body).Decode(out)
}

// GetJSONWithHeaders performs a GET request, decodes the JSON response, and
// returns the response headers. Useful when callers need header values like
// X-Total-Count for pagination.
func (c *APIClient) GetJSONWithHeaders(ctx context.Context, path string, out any) (http.Header, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, c.BaseURL+path, nil)
	if err != nil {
		return nil, err
	}
	c.setHeaders(req)

	resp, err := c.HTTPClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 400 {
		data, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
		return nil, fmt.Errorf("GET %s returned %d: %s", path, resp.StatusCode, strings.TrimSpace(string(data)))
	}
	if out != nil {
		if err := json.NewDecoder(resp.Body).Decode(out); err != nil {
			return resp.Header, err
		}
	}
	return resp.Header, nil
}

// DeleteJSON performs a DELETE request.
func (c *APIClient) DeleteJSON(ctx context.Context, path string) error {
	req, err := http.NewRequestWithContext(ctx, http.MethodDelete, c.BaseURL+path, nil)
	if err != nil {
		return err
	}
	c.setHeaders(req)

	resp, err := c.HTTPClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 400 {
		data, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
		return fmt.Errorf("DELETE %s returned %d: %s", path, resp.StatusCode, strings.TrimSpace(string(data)))
	}
	return nil
}

// PostJSON performs a POST request with a JSON body.
func (c *APIClient) PostJSON(ctx context.Context, path string, body any, out any) error {
	data, err := json.Marshal(body)
	if err != nil {
		return err
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.BaseURL+path, bytes.NewReader(data))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")
	c.setHeaders(req)

	resp, err := c.HTTPClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 400 {
		respData, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
		return fmt.Errorf("POST %s returned %d: %s", path, resp.StatusCode, strings.TrimSpace(string(respData)))
	}
	if out == nil {
		return nil
	}
	return json.NewDecoder(resp.Body).Decode(out)
}

// PutJSON performs a PUT request with a JSON body.
func (c *APIClient) PutJSON(ctx context.Context, path string, body any, out any) error {
	data, err := json.Marshal(body)
	if err != nil {
		return err
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPut, c.BaseURL+path, bytes.NewReader(data))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")
	c.setHeaders(req)

	resp, err := c.HTTPClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 400 {
		respData, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
		return fmt.Errorf("PUT %s returned %d: %s", path, resp.StatusCode, strings.TrimSpace(string(respData)))
	}
	if out == nil {
		return nil
	}
	return json.NewDecoder(resp.Body).Decode(out)
}

// UploadFile uploads a file via multipart form to /api/upload-file.
// It returns the attachment ID from the server response.
func (c *APIClient) UploadFile(ctx context.Context, fileData []byte, filename string, issueID string) (string, error) {
	var body bytes.Buffer
	writer := multipart.NewWriter(&body)

	part, err := writer.CreateFormFile("file", filepath.Base(filename))
	if err != nil {
		return "", fmt.Errorf("create form file: %w", err)
	}
	if _, err := part.Write(fileData); err != nil {
		return "", fmt.Errorf("write file data: %w", err)
	}

	if issueID != "" {
		if err := writer.WriteField("issue_id", issueID); err != nil {
			return "", fmt.Errorf("write issue_id field: %w", err)
		}
	}

	if err := writer.Close(); err != nil {
		return "", fmt.Errorf("close multipart writer: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.BaseURL+"/api/upload-file", &body)
	if err != nil {
		return "", err
	}
	req.Header.Set("Content-Type", writer.FormDataContentType())
	c.setHeaders(req)

	resp, err := c.HTTPClient.Do(req)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 400 {
		respData, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
		return "", fmt.Errorf("upload file returned %d: %s", resp.StatusCode, strings.TrimSpace(string(respData)))
	}

	var result map[string]any
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
		return "", fmt.Errorf("decode upload response: %w", err)
	}

	id, _ := result["id"].(string)
	if id == "" {
		return "", fmt.Errorf("upload response missing attachment id")
	}
	return id, nil
}

// DownloadFile downloads a file from the given URL and returns the response body.
// This is used for downloading attachments via their signed download_url.
// Downloads are limited to 100 MB to match the upload size limit.
func (c *APIClient) DownloadFile(ctx context.Context, downloadURL string) ([]byte, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, downloadURL, nil)
	if err != nil {
		return nil, err
	}

	resp, err := c.HTTPClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 400 {
		body, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
		return nil, fmt.Errorf("download returned %d: %s", resp.StatusCode, strings.TrimSpace(string(body)))
	}

	const maxDownloadSize = 100 << 20 // 100 MB
	return io.ReadAll(io.LimitReader(resp.Body, maxDownloadSize))
}

// HealthCheck hits the /health endpoint and returns the response body.
func (c *APIClient) HealthCheck(ctx context.Context) (string, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, c.BaseURL+"/health", nil)
	if err != nil {
		return "", err
	}
	resp, err := c.HTTPClient.Do(req)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

	data, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
	if resp.StatusCode >= 400 {
		return "", fmt.Errorf("health check returned %d: %s", resp.StatusCode, strings.TrimSpace(string(data)))
	}
	return strings.TrimSpace(string(data)), nil
}
