package gitea

import (
	"bytes"
	"context"
	"encoding/base64"
	"fmt"
	"path"
	"sort"
	"strings"
)

type CodeSearchHit struct {
	Path    string  `json:"path"`
	Snippet string  `json:"snippet"`
	HTMLURL string  `json:"html_url"`
	Score   float64 `json:"score,omitempty"`
}

// codeSearchMaxFiles bounds how many files a single SearchCode call will fetch
// and scan, so one call against a huge repo can't run indefinitely.
const codeSearchMaxFiles = 2000

// codeSearchMaxFileSize skips blobs larger than this (per the tree listing,
// before any fetch) — almost certainly binary/vendor/generated content, not
// worth the cost of fetching just to reject.
const codeSearchMaxFileSize = 512 * 1024

// codeSearchBinaryExts are skipped WITHOUT fetching — a cheap pre-filter for
// obviously-binary content by extension, checked against the tree listing.
var codeSearchBinaryExts = map[string]bool{
	".png": true, ".jpg": true, ".jpeg": true, ".gif": true, ".ico": true, ".webp": true, ".bmp": true,
	".pdf": true, ".zip": true, ".tar": true, ".gz": true, ".bz2": true, ".xz": true, ".7z": true,
	".exe": true, ".dll": true, ".so": true, ".dylib": true, ".bin": true, ".class": true, ".jar": true,
	".woff": true, ".woff2": true, ".ttf": true, ".eot": true, ".otf": true,
	".mp3": true, ".mp4": true, ".mov": true, ".avi": true, ".webm": true,
	".pyc": true, ".o": true, ".a": true,
}

// SearchCode does a client-side "git grep"-equivalent search. Gitea's REST API
// has no code-content-search endpoint — confirmed against a live 1.25.5
// instance's swagger spec (only /repos/search, /repos/issues/search,
// /topics/search etc exist). The web UI's OWN code search falls back to
// server-side `git grep` because no Repository Indexer is enabled on that
// instance, and that fallback is an HTML-only route, not JSON API. So this
// walks the tree, fetches text-like blobs (bounded by codeSearchMaxFiles /
// codeSearchMaxFileSize), and substring-matches q — case-insensitive, literal
// (not a regex, to keep behavior predictable and avoid a ReDoS surface from
// user-supplied input) — against file contents.
//
// Pagination is over the FULL sorted result set, recomputed on every call —
// there is no server-side index to page through incrementally, so requesting
// page 2 re-scans the tree. Acceptable for the repo sizes this targets; a real
// indexer (bleve/elasticsearch) enabled server-side would be the long-term
// fix, and is an infra decision, not something gitea-mcp controls.
func (c *Client) SearchCode(ctx context.Context, owner, repo, q string, page, limit int) ([]CodeSearchHit, error) {
	if q == "" {
		return nil, fmt.Errorf("q is required: %w", ErrValidation)
	}
	if page < 1 {
		page = 1
	}
	if limit < 1 {
		limit = 30
	}

	r, err := c.GetRepo(ctx, owner, repo)
	if err != nil {
		return nil, fmt.Errorf("resolve repo: %w", err)
	}
	branch := r.DefaultBranch
	if branch == "" {
		branch = "main"
	}

	tree, err := c.GetTree(ctx, owner, repo, branch, true)
	if err != nil {
		return nil, fmt.Errorf("tree walk: %w", err)
	}

	qLower := strings.ToLower(q)
	all := make([]CodeSearchHit, 0)
	scanned := 0
	for _, e := range tree.Tree {
		if ctx.Err() != nil {
			break
		}
		if e.Type != "blob" {
			continue
		}
		if codeSearchBinaryExts[strings.ToLower(path.Ext(e.Path))] {
			continue
		}
		if e.Size > codeSearchMaxFileSize {
			continue
		}
		if scanned >= codeSearchMaxFiles {
			break
		}
		scanned++

		fc, ferr := c.GetFileContents(ctx, owner, repo, e.Path, branch)
		if ferr != nil {
			continue // vanished/unreadable between tree walk and read — skip, don't fail the whole search
		}
		decoded, derr := base64.StdEncoding.DecodeString(fc.Content)
		if derr != nil {
			continue
		}
		if bytes.IndexByte(decoded, 0) >= 0 {
			continue // binary content the extension filter missed
		}

		content := string(decoded)
		contentLower := strings.ToLower(content)
		count := strings.Count(contentLower, qLower)
		if count == 0 {
			continue
		}

		idx := strings.Index(contentLower, qLower)
		all = append(all, CodeSearchHit{
			Path:    e.Path,
			Snippet: codeSearchSnippet(content, idx, len(q)),
			HTMLURL: fmt.Sprintf("%s/%s/%s/src/branch/%s/%s", c.baseURL, owner, repo, branch, e.Path),
			Score:   float64(count),
		})
	}

	sort.Slice(all, func(i, j int) bool {
		if all[i].Score != all[j].Score {
			return all[i].Score > all[j].Score
		}
		return all[i].Path < all[j].Path
	})

	start := (page - 1) * limit
	if start >= len(all) {
		return []CodeSearchHit{}, nil
	}
	end := start + limit
	if end > len(all) {
		end = len(all)
	}
	return all[start:end], nil
}

// codeSearchSnippet returns a short window of text centered on a match,
// trimmed to a single line-ish window so results read like a grep hit rather
// than a content dump.
func codeSearchSnippet(content string, idx, matchLen int) string {
	const window = 60
	start := idx - window
	if start < 0 {
		start = 0
	}
	end := idx + matchLen + window
	if end > len(content) {
		end = len(content)
	}
	snippet := strings.ReplaceAll(content[start:end], "\n", " ")
	return strings.TrimSpace(snippet)
}