package main

import (
    "./ui"
)

const (
    ModAlt rune     = 1 << 31 - 1
)


// A command
type Command struct {
    Name        string
    Doc         string
    Action      func(ctx CommandContext) error
}

// Execute the command
func (cmd *Command) Do(ctx CommandContext) error {
    return cmd.Action(ctx)
}


// The command context
type CommandContext interface {
    // Returns the current frame.  If no frame is defined, returns nil.
    Frame() *Frame
}

// A command mapping
type CommandMapping struct {
    Commands        map[string]*Command
    KeyMappings      map[rune]*Command
}

// Creates a new, empty command mapping
func NewCommandMapping() *CommandMapping {
    return &CommandMapping{make(map[string]*Command), make(map[rune]*Command)}
}

// Adds a new command
func (cm *CommandMapping) Define(name string, doc string, opts string, fn func(ctx CommandContext) error) {
    cm.Commands[name] = &Command{name, doc, fn}
}

// Adds a key mapping
func (cm *CommandMapping) MapKey(key rune, cmd *Command) {
    cm.KeyMappings[key] = cmd
}

// Searches for a command by name.  Returns the command or null
func (cm *CommandMapping) Command(name string) *Command {
    return cm.Commands[name]
}

// Searches for a command by key mapping
func (cm *CommandMapping) KeyMapping(key rune) *Command {
    return cm.KeyMappings[key]
}

// Registers the standard view navigation commands.  These commands require the frame
func (cm *CommandMapping) RegisterViewCommands() {
    cm.Define("move-down",  "Moves the cursor down one row", "",        gridNavOperation(func(grid *ui.Grid) { grid.MoveBy(0, 1) }))
    cm.Define("move-up",    "Moves the cursor up one row", "",          gridNavOperation(func(grid *ui.Grid) { grid.MoveBy(0, -1) }))
    cm.Define("move-left",  "Moves the cursor left one column", "",     gridNavOperation(func(grid *ui.Grid) { grid.MoveBy(-1, 0) }))
    cm.Define("move-right", "Moves the cursor right one column", "",    gridNavOperation(func(grid *ui.Grid) { grid.MoveBy(1, 0) }))

    // TODO: Pages are just 25 rows and 15 columns at the moment
    cm.Define("page-down",  "Moves the cursor down one page", "",       gridNavOperation(func(grid *ui.Grid) { grid.MoveBy(0, 25) }))
    cm.Define("page-up",    "Moves the cursor up one page", "",         gridNavOperation(func(grid *ui.Grid) { grid.MoveBy(0, -25) }))
    cm.Define("page-left",  "Moves the cursor left one page", "",       gridNavOperation(func(grid *ui.Grid) { grid.MoveBy(-15, 0) }))
    cm.Define("page-right", "Moves the cursor right one page", "",      gridNavOperation(func(grid *ui.Grid) { grid.MoveBy(15, 0) }))

    cm.Define("row-top",    "Moves the cursor to the top of the row", "",     gridNavOperation(func(grid *ui.Grid) { 
        cellX, _ := grid.CellPosition()
        grid.MoveTo(cellX, 0)
    }))
    cm.Define("row-bottom", "Moves the cursor to the bottom of the row", "",  gridNavOperation(func(grid *ui.Grid) {
        cellX, _ := grid.CellPosition()
        _, dimY := grid.Model().Dimensions()
        grid.MoveTo(cellX, dimY - 1)
    }))        
    cm.Define("col-left",   "Moves the cursor to the left-most column", "",   gridNavOperation(func(grid *ui.Grid) {
        _, cellY := grid.CellPosition()
        grid.MoveTo(0, cellY)
    }))

    cm.Define("col-right",  "Moves the cursor to the right-most column", "",  gridNavOperation(func(grid *ui.Grid) {
        _, cellY := grid.CellPosition()
        dimX, _ := grid.Model().Dimensions()
        grid.MoveTo(dimX - 1, cellY)
    }))        
}

// Registers the standard view key bindings.  These commands require the frame
func (cm *CommandMapping) RegisterViewKeyBindings() {
    cm.MapKey('i', cm.Command("move-up"))
    cm.MapKey('k', cm.Command("move-down"))
    cm.MapKey('j', cm.Command("move-left"))
    cm.MapKey('l', cm.Command("move-right"))
    cm.MapKey('I', cm.Command("page-up"))
    cm.MapKey('K', cm.Command("page-down"))
    cm.MapKey('J', cm.Command("page-left"))
    cm.MapKey('L', cm.Command("page-right"))
    cm.MapKey(ui.KeyCtrlI, cm.Command("row-top"))
    cm.MapKey(ui.KeyCtrlK, cm.Command("row-bottom"))
    cm.MapKey(ui.KeyCtrlJ, cm.Command("col-left"))
    cm.MapKey(ui.KeyCtrlL, cm.Command("col-right"))

    cm.MapKey(ui.KeyArrowUp, cm.Command("move-up"))
    cm.MapKey(ui.KeyArrowDown, cm.Command("move-down"))
    cm.MapKey(ui.KeyArrowLeft, cm.Command("move-left"))
    cm.MapKey(ui.KeyArrowRight, cm.Command("move-right"))
}


// A nativation command factory.  This will perform the passed in operation with the current grid and
// will display the cell value in the message box.
func gridNavOperation(op func(grid *ui.Grid)) func(ctx CommandContext) error {
    return func(ctx CommandContext) error {
        op(ctx.Frame().Grid())
        ctx.Frame().ShowCellValue()
        return nil
    }
}