package progdoc

import (
	"bufio"
	"io"
	"strings"
)

type goFileMeta struct {
	Name  string
	Value string
}

type goFilePart struct {
	Meta []goFileMeta
	Body string
}

func (g goFilePart) FirstMeta(name string) string {
	for _, meta := range g.Meta {
		if meta.Name == name {
			return meta.Value
		}
	}
	return ""
}

type goFileDocs struct {
	Parts []goFilePart
}

func (g goFileDocs) PartsWithMeta(name string) []goFilePart {
	var parts []goFilePart
	for _, part := range g.Parts {
		if part.FirstMeta(name) != "" {
			parts = append(parts, part)
		}
	}
	return parts
}

func (g goFileDocs) FirstPartWithMeta(name string) goFilePart {
	parts := g.PartsWithMeta(name)
	if len(parts) > 0 {
		return parts[0]
	}
	return goFilePart{}
}

func (g goFileDocs) HasDocs() bool {
	return len(g.Parts) > 0
}

func parseGoFileDocs(r io.Reader) (goFileDocs, error) {
	scanner := bufio.NewScanner(r)
	var docs goFileDocs
	var currentPart *goFilePart
	var inDocBlock bool

	for scanner.Scan() {
		line := scanner.Text()
		trimmed := strings.TrimSpace(line)

		// Check if this is the start of a doc block (///)
		if strings.HasPrefix(trimmed, "///") {
			// Finalize previous part if exists
			if currentPart != nil {
				currentPart.Body = strings.TrimSpace(currentPart.Body)
				docs.Parts = append(docs.Parts, *currentPart)
			}
			// Start a new part
			currentPart = &goFilePart{}
			inDocBlock = true

			// Process the first line content after ///
			content := strings.TrimPrefix(trimmed, "///")
			content = strings.TrimPrefix(content, " ")
			if content != "" {
				processPart(currentPart, content)
			}
			continue
		}

		// Check if this continues a doc block (//)
		if inDocBlock && strings.HasPrefix(trimmed, "//") && !strings.HasPrefix(trimmed, "///") {
			// Extract content after //
			content := strings.TrimPrefix(trimmed, "//")
			content = strings.TrimPrefix(content, " ")
			processPart(currentPart, content)
			continue
		}

		// If we hit a non-comment line, end the doc block
		if inDocBlock && !strings.HasPrefix(trimmed, "//") {
			inDocBlock = false
			if currentPart != nil {
				currentPart.Body = strings.TrimSpace(currentPart.Body)
				docs.Parts = append(docs.Parts, *currentPart)
				currentPart = nil
			}
		}
	}

	// Finalize any remaining part
	if currentPart != nil {
		currentPart.Body = strings.TrimSpace(currentPart.Body)
		docs.Parts = append(docs.Parts, *currentPart)
	}

	if err := scanner.Err(); err != nil {
		return goFileDocs{}, err
	}

	return docs, nil
}

func processPart(part *goFilePart, line string) {
	// Check if this is a meta line (starts with :)
	if strings.HasPrefix(line, ":") {
		// Parse meta value
		rest := strings.TrimPrefix(line, ":")
		fields := strings.Fields(rest)
		if len(fields) > 0 {
			name := fields[0]
			value := strings.Join(fields[1:], " ")
			part.Meta = append(part.Meta, goFileMeta{Name: name, Value: value})
		}
	} else {
		// Add to body
		if part.Body != "" {
			part.Body += "\n"
		}
		part.Body += line
	}
}