package main

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

const defaultBrainURL = "http://koala:30330"

// brainClient calls the brain HTTP REST API exposed alongside the MCP
// endpoint at the same host:port. /mcp serves MCP framing; /query and /write
// serve plain REST. We use the REST surface because the CLI is a
// shell-friendly client; MCP framing is unnecessary.
type brainClient struct {
	baseURL string
	http    *http.Client
}

func newBrainClient() *brainClient {
	u := os.Getenv("BRAIN_URL")
	if u == "" {
		u = defaultBrainURL
	}
	return &brainClient{
		baseURL: u,
		http:    &http.Client{Timeout: 5 * time.Second},
	}
}

// QueryHit mirrors a single result from the brain's /query endpoint.
type QueryHit struct {
	Path    string `json:"path"`
	Title   string `json:"title"`
	Excerpt string `json:"excerpt"`
	Score   int    `json:"score"`
}

// QueryResult mirrors the /query response envelope.
type QueryResult struct {
	Results []QueryHit `json:"results"`
}

func (c *brainClient) Query(ctx context.Context, topic string, limit int) (*QueryResult, error) {
	payload, err := json.Marshal(struct {
		Query string `json:"query"`
		Limit int    `json:"limit"`
	}{Query: topic, Limit: limit})
	if err != nil {
		return nil, fmt.Errorf("marshal payload: %w", err)
	}

	u := c.baseURL + "/query"
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, u, bytes.NewReader(payload))
	if err != nil {
		return nil, fmt.Errorf("build request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.http.Do(req)
	if err != nil {
		return nil, fmt.Errorf("brain POST /query: %w", err)
	}
	defer func() { _ = resp.Body.Close() }()
	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("brain POST /query: status %d: %s", resp.StatusCode, string(body))
	}
	var out QueryResult
	if err := json.NewDecoder(resp.Body).Decode(&out); err != nil {
		return nil, fmt.Errorf("decode /query response: %w", err)
	}
	return &out, nil
}

// WriteResult mirrors the /write response envelope.
type WriteResult struct {
	Path string `json:"path"`
}

func (c *brainClient) Write(ctx context.Context, kind, slug string, content io.Reader) (*WriteResult, error) {
	body, err := io.ReadAll(content)
	if err != nil {
		return nil, fmt.Errorf("read content: %w", err)
	}
	payload, err := json.Marshal(struct {
		Type    string `json:"type"`
		Slug    string `json:"slug"`
		Content string `json:"content"`
	}{Type: kind, Slug: slug, Content: string(body)})
	if err != nil {
		return nil, fmt.Errorf("marshal payload: %w", err)
	}

	u := c.baseURL + "/write"
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, u, bytes.NewReader(payload))
	if err != nil {
		return nil, fmt.Errorf("build request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.http.Do(req)
	if err != nil {
		return nil, fmt.Errorf("brain POST /write: %w", err)
	}
	defer func() { _ = resp.Body.Close() }()
	if resp.StatusCode != http.StatusOK {
		respBody, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("brain POST /write: status %d: %s", resp.StatusCode, string(respBody))
	}
	var out WriteResult
	if err := json.NewDecoder(resp.Body).Decode(&out); err != nil {
		return nil, fmt.Errorf("decode /write response: %w", err)
	}
	return &out, nil
}

// PassRateResult mirrors the /pass-rate response envelope.
type PassRateResult struct {
	Skill    string   `json:"skill"`
	Window   string   `json:"window"`
	Pass     int      `json:"pass"`
	Fail     int      `json:"fail"`
	Skip     int      `json:"skip"`
	Total    int      `json:"total"`
	PassRate *float64 `json:"pass_rate"`
}

func (c *brainClient) PassRate(ctx context.Context, skill, window string) (*PassRateResult, error) {
	q := url.Values{}
	q.Set("skill", skill)
	q.Set("window", window)
	u := c.baseURL + "/pass-rate?" + q.Encode()

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u, nil)
	if err != nil {
		return nil, fmt.Errorf("build request: %w", err)
	}
	resp, err := c.http.Do(req)
	if err != nil {
		return nil, fmt.Errorf("brain GET /pass-rate: %w", err)
	}
	defer func() { _ = resp.Body.Close() }()
	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("brain GET /pass-rate: status %d: %s", resp.StatusCode, string(body))
	}
	var out PassRateResult
	if err := json.NewDecoder(resp.Body).Decode(&out); err != nil {
		return nil, fmt.Errorf("decode /pass-rate response: %w", err)
	}
	return &out, nil
}