// Package client provides a synchronous facade over foreman's async /jobs API.
//
// Why: orchestration callers need a simple blocking call to submit chat work
// to a foreman daemon without managing webhooks or polling themselves. This is
// the Level 1 integration described in ADR-0011.
// What: submits a job via POST /jobs, waits for completion using either a local
// webhook receiver (preferred) or polling fallback, and returns the result.
// Test: spin up a real foreman server via internal packages, submit jobs through
// the client, verify results for happy path, failure, timeout, and auth.
package client

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"time"
)

// Client communicates with a foreman daemon's async /jobs API.
type Client struct {
	baseURL       string
	token         string
	webhookSecret string
	httpClient    *http.Client
	pollInterval  time.Duration
	forcePolling  bool
}

// Option configures a Client.
type Option func(*Client)

// New creates a new foreman client targeting the given base URL.
//
// Why: callers need a single entry point with sensible defaults and optional overrides.
// What: returns a Client configured with the base URL and any provided options.
// Test: create with New, verify baseURL is trimmed and defaults are applied.
func New(baseURL string, opts ...Option) *Client {
	c := &Client{
		baseURL:      baseURL,
		httpClient:   &http.Client{Timeout: 0}, // no global timeout; per-request via context
		pollInterval: 2 * time.Second,
	}
	for _, opt := range opts {
		opt(c)
	}
	return c
}

// WithToken sets the bearer token for authenticating with foreman.
//
// Why: foreman supports optional static bearer auth (ADR-0010).
// What: configures the Authorization header on all outbound requests.
// Test: create with WithToken, submit a job, verify the header is present.
func WithToken(token string) Option {
	return func(c *Client) {
		c.token = token
	}
}

// WithWebhookSecret sets the HMAC secret for verifying inbound webhook payloads.
//
// Why: callers receiving webhooks need to verify authenticity (ADR-0005).
// What: stores the secret for HMAC-SHA256 verification on received events.
// Test: create with a secret, receive a webhook, verify signature check passes.
func WithWebhookSecret(secret string) Option {
	return func(c *Client) {
		c.webhookSecret = secret
	}
}

// WithHTTPClient sets a custom HTTP client for outbound requests.
//
// Why: callers may need custom TLS, timeouts, or transport settings.
// What: replaces the default http.Client.
// Test: create with a custom client, verify it is used for requests.
func WithHTTPClient(hc *http.Client) Option {
	return func(c *Client) {
		c.httpClient = hc
	}
}

// WithPollInterval sets the interval for polling GET /jobs/{id} in fallback mode.
//
// Why: the default 2s may be too frequent or too slow for some callers.
// What: overrides the default poll interval.
// Test: create with a custom interval, verify polling uses it.
func WithPollInterval(d time.Duration) Option {
	return func(c *Client) {
		c.pollInterval = d
	}
}

// WithPollingMode forces the client to use polling instead of attempting a
// webhook receiver. Useful when the caller knows it is behind NAT or a firewall.
//
// Why: webhook receivers require the foreman daemon to reach back to the caller,
// which is not always possible (NAT, firewalls, containers).
// What: disables the webhook receiver attempt and uses polling exclusively.
// Test: create with WithPollingMode, verify no listener is started.
func WithPollingMode() Option {
	return func(c *Client) {
		c.forcePolling = true
	}
}

// SubmitRequest is the payload for submitting a job to foreman.
type SubmitRequest struct {
	Model    string            `json:"model"`
	Messages []json.RawMessage `json:"messages"`
	Stream   *bool             `json:"stream,omitempty"`
	Tools    json.RawMessage   `json:"tools,omitempty"`
	Options  json.RawMessage   `json:"options,omitempty"`
	Think    json.RawMessage   `json:"think,omitempty"`
}

// Result is the final outcome of a submitted job.
type Result struct {
	JobID       string          `json:"job_id"`
	State       string          `json:"state"`
	Model       string          `json:"model"`
	Attempt     int             `json:"attempt"`
	Result      json.RawMessage `json:"result,omitempty"`
	Error       string          `json:"error,omitempty"`
	Artifacts   []Artifact      `json:"artifacts,omitempty"`
	CreatedAt   time.Time       `json:"created_at"`
	CompletedAt *time.Time      `json:"completed_at,omitempty"`
}

// Artifact is metadata and optional inline data for a job artifact.
type Artifact struct {
	Name        string `json:"name"`
	ContentType string `json:"content_type"`
	Size        int64  `json:"size"`
	Data        string `json:"data,omitempty"`
	URL         string `json:"url,omitempty"`
}

// ModelInfo describes an installed model, as returned by GET /api/tags.
type ModelInfo struct {
	Name       string          `json:"name"`
	Model      string          `json:"model"`
	ModifiedAt time.Time       `json:"modified_at"`
	Size       int64           `json:"size"`
	Digest     string          `json:"digest"`
	Details    json.RawMessage `json:"details,omitempty"`
}

// EmbedRequest is the payload for the embedding endpoint.
type EmbedRequest struct {
	Model     string          `json:"model"`
	Input     json.RawMessage `json:"input"`
	KeepAlive json.RawMessage `json:"keep_alive,omitempty"`
	Options   json.RawMessage `json:"options,omitempty"`
}

// EmbedResponse is the response from the embedding endpoint.
type EmbedResponse struct {
	Model      string      `json:"model,omitempty"`
	Embeddings [][]float64 `json:"embeddings,omitempty"`
}

// jobSubmitRequest is the wire format for POST /jobs on the foreman server.
type jobSubmitRequest struct {
	Model           string            `json:"model"`
	Messages        []json.RawMessage `json:"messages"`
	Stream          *bool             `json:"stream,omitempty"`
	Tools           json.RawMessage   `json:"tools,omitempty"`
	Options         json.RawMessage   `json:"options,omitempty"`
	Think           json.RawMessage   `json:"think,omitempty"`
	StateWebhookURL string            `json:"state_webhook_url,omitempty"`
}

// jobSubmitResponse is the wire format for the POST /jobs response.
type jobSubmitResponse struct {
	JobID string `json:"job_id"`
}

// jobStatusResponse mirrors the GET /jobs/{id} response from the foreman server.
type jobStatusResponse struct {
	JobID       string     `json:"job_id"`
	State       string     `json:"state"`
	Model       string     `json:"model"`
	CreatedAt   time.Time  `json:"created_at"`
	StartedAt   *time.Time `json:"started_at"`
	CompletedAt *time.Time `json:"completed_at"`
	Attempt     int        `json:"attempt"`
	Result      json.RawMessage `json:"result"`
	Error       *string         `json:"error"`
	Artifacts   []Artifact      `json:"artifacts"`
}

// tagsResponse mirrors the GET /api/tags response.
type tagsResponse struct {
	Models []ModelInfo `json:"models"`
}

// Submit sends a chat job to foreman and blocks until it completes or the context
// is cancelled. It attempts to use a local webhook receiver for push notification;
// if that fails (or forcePolling is set), it falls back to polling GET /jobs/{id}.
//
// Why: orchestration callers want a synchronous call signature over the async API
// without managing their own webhook infrastructure.
// What: POSTs to /jobs, waits for terminal state via webhook or polling, returns
// the final result or error.
// Test: submit a job to a test server, verify the returned Result contains the
// completion, artifacts, and correct state.
func (c *Client) Submit(ctx context.Context, req SubmitRequest) (*Result, error) {
	if req.Model == "" {
		return nil, fmt.Errorf("model is required")
	}

	// Attempt webhook receiver mode first, fall back to polling.
	if !c.forcePolling {
		result, err := c.submitWithWebhook(ctx, req)
		if err == nil {
			return result, nil
		}
		// If the webhook listener failed to bind, fall back to polling.
		// Any other error (context cancelled, server error) is returned directly.
		if !isBindError(err) {
			return nil, err
		}
	}

	return c.submitWithPolling(ctx, req)
}

// submitWithPolling submits a job and polls GET /jobs/{id} until a terminal state.
func (c *Client) submitWithPolling(ctx context.Context, req SubmitRequest) (*Result, error) {
	wireReq := jobSubmitRequest{
		Model:    req.Model,
		Messages: req.Messages,
		Stream:   req.Stream,
		Tools:    req.Tools,
		Options:  req.Options,
		Think:    req.Think,
	}

	jobID, err := c.postJob(ctx, wireReq)
	if err != nil {
		return nil, fmt.Errorf("submit job: %w", err)
	}

	return c.pollUntilDone(ctx, jobID)
}

// postJob POSTs a job to the foreman server and returns the job ID.
func (c *Client) postJob(ctx context.Context, req jobSubmitRequest) (string, error) {
	body, err := json.Marshal(req)
	if err != nil {
		return "", fmt.Errorf("marshal job request: %w", err)
	}

	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+"/jobs", bytes.NewReader(body))
	if err != nil {
		return "", fmt.Errorf("create POST /jobs request: %w", err)
	}
	httpReq.Header.Set("Content-Type", "application/json")
	c.setAuth(httpReq)

	resp, err := c.httpClient.Do(httpReq)
	if err != nil {
		return "", fmt.Errorf("POST /jobs: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusAccepted {
		var errResp struct {
			Error string `json:"error"`
		}
		json.NewDecoder(resp.Body).Decode(&errResp)
		return "", fmt.Errorf("POST /jobs returned %d: %s", resp.StatusCode, errResp.Error)
	}

	var submitResp jobSubmitResponse
	if err := json.NewDecoder(resp.Body).Decode(&submitResp); err != nil {
		return "", fmt.Errorf("decode POST /jobs response: %w", err)
	}

	return submitResp.JobID, nil
}

// pollUntilDone polls GET /jobs/{id} at pollInterval until the job reaches a
// terminal state (done or failed) or the context is cancelled.
func (c *Client) pollUntilDone(ctx context.Context, jobID string) (*Result, error) {
	ticker := time.NewTicker(c.pollInterval)
	defer ticker.Stop()

	for {
		status, err := c.getJobStatus(ctx, jobID)
		if err != nil {
			return nil, fmt.Errorf("poll job %s: %w", jobID, err)
		}

		if status.State == "done" || status.State == "failed" {
			return statusToResult(status), nil
		}

		select {
		case <-ctx.Done():
			return nil, fmt.Errorf("context cancelled while polling job %s: %w", jobID, ctx.Err())
		case <-ticker.C:
		}
	}
}

// getJobStatus fetches the current state of a job via GET /jobs/{id}.
func (c *Client) getJobStatus(ctx context.Context, jobID string) (*jobStatusResponse, error) {
	httpReq, err := http.NewRequestWithContext(ctx, http.MethodGet, c.baseURL+"/jobs/"+jobID, nil)
	if err != nil {
		return nil, fmt.Errorf("create GET /jobs/%s request: %w", jobID, err)
	}
	c.setAuth(httpReq)

	resp, err := c.httpClient.Do(httpReq)
	if err != nil {
		return nil, fmt.Errorf("GET /jobs/%s: %w", jobID, err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		var errResp struct {
			Error string `json:"error"`
		}
		json.NewDecoder(resp.Body).Decode(&errResp)
		return nil, fmt.Errorf("GET /jobs/%s returned %d: %s", jobID, resp.StatusCode, errResp.Error)
	}

	var status jobStatusResponse
	if err := json.NewDecoder(resp.Body).Decode(&status); err != nil {
		return nil, fmt.Errorf("decode GET /jobs/%s response: %w", jobID, err)
	}

	return &status, nil
}

// Tags returns the list of models installed on the foreman target.
//
// Why: callers need to discover available models before submitting work.
// What: GETs /api/tags and returns parsed model info.
// Test: call Tags on a test server with known models, verify the list matches.
func (c *Client) Tags(ctx context.Context) ([]ModelInfo, error) {
	httpReq, err := http.NewRequestWithContext(ctx, http.MethodGet, c.baseURL+"/api/tags", nil)
	if err != nil {
		return nil, fmt.Errorf("create GET /api/tags request: %w", err)
	}
	c.setAuth(httpReq)

	resp, err := c.httpClient.Do(httpReq)
	if err != nil {
		return nil, fmt.Errorf("GET /api/tags: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("GET /api/tags returned %d", resp.StatusCode)
	}

	var tags tagsResponse
	if err := json.NewDecoder(resp.Body).Decode(&tags); err != nil {
		return nil, fmt.Errorf("decode /api/tags response: %w", err)
	}

	return tags.Models, nil
}

// Embed sends an embedding request to the foreman target. Embeddings bypass the
// queue and are proxied directly to the always-resident embedder (ADR-0013).
//
// Why: callers need embeddings without waiting behind chat jobs in the queue.
// What: POSTs to /api/embed and returns the parsed response.
// Test: call Embed on a test server with a stub embedder, verify embeddings returned.
func (c *Client) Embed(ctx context.Context, req EmbedRequest) (*EmbedResponse, error) {
	body, err := json.Marshal(req)
	if err != nil {
		return nil, fmt.Errorf("marshal embed request: %w", err)
	}

	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+"/api/embed", bytes.NewReader(body))
	if err != nil {
		return nil, fmt.Errorf("create POST /api/embed request: %w", err)
	}
	httpReq.Header.Set("Content-Type", "application/json")
	c.setAuth(httpReq)

	resp, err := c.httpClient.Do(httpReq)
	if err != nil {
		return nil, fmt.Errorf("POST /api/embed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("POST /api/embed returned %d", resp.StatusCode)
	}

	var embedResp EmbedResponse
	if err := json.NewDecoder(resp.Body).Decode(&embedResp); err != nil {
		return nil, fmt.Errorf("decode /api/embed response: %w", err)
	}

	return &embedResp, nil
}

// setAuth adds the bearer token to the request if configured.
func (c *Client) setAuth(req *http.Request) {
	if c.token != "" {
		req.Header.Set("Authorization", "Bearer "+c.token)
	}
}

// statusToResult converts a jobStatusResponse to a Result.
func statusToResult(s *jobStatusResponse) *Result {
	r := &Result{
		JobID:       s.JobID,
		State:       s.State,
		Model:       s.Model,
		Attempt:     s.Attempt,
		Result:      s.Result,
		Artifacts:   s.Artifacts,
		CreatedAt:   s.CreatedAt,
		CompletedAt: s.CompletedAt,
	}
	if s.Error != nil {
		r.Error = *s.Error
	}
	if r.Artifacts == nil {
		r.Artifacts = []Artifact{}
	}
	return r
}