// ingestion/internal/extract/extract.go
package extract

import (
	"fmt"
	"io"
	"os"
	"strings"
)

// Text reads the file at path and returns its plain-text content.
// Supported extensions: .md, .txt (passthrough), .pdf (via pdftotext),
// .docx/.xlsx/.pptx/.png/.jpg/.jpeg (via docmark, ADR-0013 -- requires
// DOCMARK_URL to be set; see docmark.go).
func Text(path string) (string, error) {
	ext := strings.ToLower(fileExt(path))
	switch ext {
	case ".md", ".txt":
		b, err := os.ReadFile(path)
		if err != nil {
			return "", fmt.Errorf("read %s: %w", path, err)
		}
		return string(b), nil
	case ".pdf":
		return extractPDF(path)
	case ".docx", ".xlsx", ".pptx", ".png", ".jpg", ".jpeg":
		return extractViaDocmark(path)
	default:
		return "", fmt.Errorf("unsupported file extension: %s", ext)
	}
}

// fileExt returns the file extension including the dot, lowercased.
func fileExt(path string) string {
	for i := len(path) - 1; i >= 0; i-- {
		if path[i] == '.' {
			return path[i:]
		}
		if path[i] == '/' || path[i] == '\\' {
			break
		}
	}
	return ""
}

// TextIn is Text for a file read through an os.Root (hyperguild#153): the
// read cannot leave the root, so a path checked earlier cannot be swapped
// for a symlink pointing elsewhere before it is read. Formats that need an
// external tool (pdf, docmark) are copied to a temp file from the handle
// opened through the root, then extracted from the copy.
func TextIn(r *os.Root, rel string) (string, error) {
	fi, err := r.Lstat(rel)
	if err != nil {
		return "", fmt.Errorf("stat %s: %w", rel, err)
	}
	if !fi.Mode().IsRegular() {
		return "", fmt.Errorf("%s: not a regular file", rel)
	}
	f, err := r.Open(rel)
	if err != nil {
		return "", fmt.Errorf("open %s: %w", rel, err)
	}
	defer func() { _ = f.Close() }()
	ext := strings.ToLower(fileExt(rel))
	switch ext {
	case ".md", ".txt":
		b, err := io.ReadAll(f)
		if err != nil {
			return "", fmt.Errorf("read %s: %w", rel, err)
		}
		return string(b), nil
	case ".pdf", ".docx", ".xlsx", ".pptx", ".png", ".jpg", ".jpeg":
		tmp, err := os.CreateTemp("", "ingest-*"+ext)
		if err != nil {
			return "", fmt.Errorf("temp copy: %w", err)
		}
		defer func() { _ = os.Remove(tmp.Name()) }()
		if _, err := io.Copy(tmp, f); err != nil {
			_ = tmp.Close()
			return "", fmt.Errorf("copy %s: %w", rel, err)
		}
		if err := tmp.Close(); err != nil {
			return "", fmt.Errorf("copy %s: %w", rel, err)
		}
		return Text(tmp.Name())
	default:
		return "", fmt.Errorf("unsupported file extension: %s", ext)
	}
}