package docsite

import (
	"errors"
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"io/fs"
	"os"
	"path/filepath"
	"regexp"
	"slices"
	"strconv"
	"strings"
)

// Commands is the set of command names docs pages may show. The caller
// collects them from the real command constructors; the checker holds no
// hard-coded list.
type Commands struct {
	// Tool lists the summer CLI command names.
	Tool []string
	// App lists the command names every application binary gets from the
	// framework (migrations, queue, serve, admin and the rest).
	App []string
}

// shellLangs are the fence languages read as shell sessions: their lines
// are checked as commands and highlighted with prompts.
var shellLangs = []string{"sh", "shell", "bash", "console"}

// commandSeparators split one shell line into its commands.
var commandSeparators = regexp.MustCompile(`&&|\|\||;|\|`)

// checkCommands verifies every summer and ./bin/<app> command name in shell
// fences and code spans of the pages. Application names may also come from
// bonfire.Command literals in docs/examples and examples.
func (s *site) checkCommands(docs []parsedDoc) ([]Problem, error) {
	if s.opts.Commands == nil {
		return []Problem{{File: s.rel(s.opts.Src), Rule: "command", Message: "no command set supplied"}}, nil
	}
	tool := map[string]bool{}
	for _, n := range s.opts.Commands.Tool {
		tool[n] = true
	}
	app := map[string]bool{}
	for _, n := range s.opts.Commands.App {
		app[n] = true
	}
	for _, dir := range []string{filepath.Join(s.opts.Src, "examples"), filepath.Join(s.opts.Root, "examples")} {
		names, err := exampleCommandNames(dir)
		if err != nil {
			return nil, err
		}
		for _, n := range names {
			app[n] = true
		}
	}
	var problems []Problem
	check := func(d parsedDoc, line int, text string) {
		for _, cmd := range commandSeparators.Split(text, -1) {
			name, isTool, ok := commandWord(cmd)
			if !ok {
				continue
			}
			known := app[name]
			if isTool {
				known = tool[name]
			}
			if !known {
				problems = append(problems, Problem{File: d.file, Line: line, Rule: "command",
					Message: fmt.Sprintf("%q is not a summer or application command", name)})
			}
		}
	}
	for _, d := range docs {
		if d.page == nil {
			continue
		}
		for _, span := range codeSpans(d.doc, d.body, d.line) {
			check(d, span.line, span.text)
		}
		fences, err := collectFences(d.doc, d.body)
		if err != nil {
			return nil, err
		}
		for _, f := range fences {
			if !slices.Contains(shellLangs, f.lang) {
				continue
			}
			for _, line := range f.code {
				check(d, d.line+line.line, line.text)
			}
		}
	}
	return problems, nil
}

// commandWord finds the summer or application command word in one shell
// command. tool is true for summer and `go run ./cmd/summer`, false for
// ./bin/{app} and bin/{app}. ok is false when the line is not one of
// those programs or when flags leave no command word. Flag handling
// matches cobra's stripFlags for a root whose only flag is the bool
// --help / -h: "--" ends the search, --help and -h take no value, any
// other --name or two-character -x consumes the next token, and a token
// that already contains "=" is skipped alone.
func commandWord(cmd string) (name string, tool bool, ok bool) {
	fields := strings.Fields(strings.TrimSpace(cmd))
	if len(fields) > 0 && fields[0] == "$" {
		fields = fields[1:]
	}
	for len(fields) > 0 && isAssignment(fields[0]) {
		fields = fields[1:]
	}
	switch {
	case len(fields) == 0:
		return "", false, false
	case fields[0] == "summer":
		tool = true
		fields = fields[1:]
	case len(fields) >= 3 && fields[0] == "go" && fields[1] == "run" && fields[2] == "./cmd/summer":
		tool = true
		fields = fields[3:]
	case isAppBin(fields[0]):
		fields = fields[1:]
	default:
		return "", false, false
	}
	for len(fields) > 0 {
		s := fields[0]
		switch {
		case s == "--":
			return "", tool, false
		case strings.HasPrefix(s, "-") && strings.Contains(s, "="):
			fields = fields[1:]
		case s == "--help" || s == "-h":
			fields = fields[1:]
		case strings.HasPrefix(s, "--") || (strings.HasPrefix(s, "-") && len(s) == 2):
			if len(fields) < 3 {
				return "", tool, false
			}
			fields = fields[2:]
		case strings.HasPrefix(s, "-"):
			fields = fields[1:]
		default:
			return s, tool, true
		}
	}
	return "", tool, false
}

// isAssignment reports a leading VAR=value token: a name of letters,
// digits and underscores that does not start with a digit.
func isAssignment(tok string) bool {
	name, _, ok := strings.Cut(tok, "=")
	if !ok || name == "" || (name[0] >= '0' && name[0] <= '9') {
		return false
	}
	for _, r := range name {
		if r != '_' && (r < '0' || r > '9') && (r < 'A' || r > 'Z') && (r < 'a' || r > 'z') {
			return false
		}
	}
	return true
}

// isAppBin reports ./bin/{app} and bin/{app}, with app in [A-Za-z0-9._-].
func isAppBin(tok string) bool {
	rest, ok := strings.CutPrefix(tok, "./bin/")
	if !ok {
		rest, ok = strings.CutPrefix(tok, "bin/")
	}
	if !ok || rest == "" || strings.Contains(rest, "/") {
		return false
	}
	for _, r := range rest {
		if r != '.' && r != '_' && r != '-' && (r < '0' || r > '9') && (r < 'A' || r > 'Z') && (r < 'a' || r > 'z') {
			return false
		}
	}
	return true
}

// exampleCommandNames returns the string-literal Name of every
// bonfire.Command composite literal (including the elided elements of a
// []bonfire.Command literal) in the non-test Go files under dir. It parses
// the files; the tool never imports example code.
func exampleCommandNames(dir string) ([]string, error) {
	if _, err := os.Stat(dir); errors.Is(err, fs.ErrNotExist) {
		return nil, nil
	}
	var names []string
	fset := token.NewFileSet()
	err := filepath.WalkDir(dir, func(p string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}
		name := d.Name()
		if d.IsDir() {
			if p != dir && (strings.HasPrefix(name, ".") || strings.HasPrefix(name, "_") || name == "testdata" || name == "node_modules" || name == "vendor") {
				return filepath.SkipDir
			}
			return nil
		}
		if !strings.HasSuffix(name, ".go") || strings.HasSuffix(name, "_test.go") {
			return nil
		}
		f, err := parser.ParseFile(fset, p, nil, parser.SkipObjectResolution)
		if err != nil {
			return fmt.Errorf("docsite: parse %s: %w", p, err)
		}
		ast.Inspect(f, func(n ast.Node) bool {
			lit, ok := n.(*ast.CompositeLit)
			if !ok {
				return true
			}
			switch {
			case isBonfireCommand(lit.Type):
				names = appendCommandName(names, lit)
			case isBonfireCommandSlice(lit.Type):
				for _, e := range lit.Elts {
					if el, ok := e.(*ast.CompositeLit); ok && el.Type == nil {
						names = appendCommandName(names, el)
					}
				}
			}
			return true
		})
		return nil
	})
	if err != nil {
		return nil, fmt.Errorf("docsite: scan %s: %w", dir, err)
	}
	return names, nil
}

func isBonfireCommand(expr ast.Expr) bool {
	sel, ok := expr.(*ast.SelectorExpr)
	if !ok {
		return false
	}
	pkg, ok := sel.X.(*ast.Ident)
	return ok && pkg.Name == "bonfire" && sel.Sel.Name == "Command"
}

func isBonfireCommandSlice(expr ast.Expr) bool {
	arr, ok := expr.(*ast.ArrayType)
	return ok && isBonfireCommand(arr.Elt)
}

func appendCommandName(names []string, lit *ast.CompositeLit) []string {
	for _, e := range lit.Elts {
		kv, ok := e.(*ast.KeyValueExpr)
		if !ok {
			continue
		}
		key, ok := kv.Key.(*ast.Ident)
		if !ok || key.Name != "Name" {
			continue
		}
		if bl, ok := kv.Value.(*ast.BasicLit); ok && bl.Kind == token.STRING {
			if v, err := strconv.Unquote(bl.Value); err == nil {
				names = append(names, v)
			}
		}
	}
	return names
}