# The contents of this file are subject to the Common Public Attribution License
# Version 1.0 (the “License”); you may not use this file except in compliance
# with the License. You may obtain a copy of the License at
# https://myou.dev/licenses/LICENSE-CPAL. The License is based on the Mozilla
# Public License Version 1.1 but Sections 14 and 15 have been added to cover use
# of software over a computer network and provide for limited attribution for
# the Original Developer. In addition, Exhibit A has been modified to be
# consistent with Exhibit B.
#
# Software distributed under the License is distributed on an “AS IS” basis,
# WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for
# the specific language governing rights and limitations under the License.
#
# The Original Code is Myou Engine.
#
# the Original Developer is the Initial Developer.
#
# The Initial Developer of the Original Code is the Myou Engine developers.
# All portions of the code written by the Myou Engine developers are Copyright
# (c) 2024. All Rights Reserved.
#
# Alternatively, the contents of this file may be used under the terms of the
# GNU Affero General Public License version 3 (the [AGPL-3] License), in which
# case the provisions of [AGPL-3] License are applicable instead of those above.
#
# If you wish to allow use of your version of this file only under the terms of
# the [AGPL-3] License and not to allow others to use your version of this file
# under the CPAL, indicate your decision by deleting the provisions above and
# replace them with the notice and other provisions required by the [AGPL-3]
# License. If you do not delete the provisions above, a recipient may use your
# version of this file under either the CPAL or the [AGPL-3] License.

import ../types
import std/options
import std/tables
import vmath except Quat

# Forward declarations
proc newFramebuffer*(engine: MyouEngine, 
        width, height: int,
        format: TextureFormat,
        depth_type: FramebufferDepthType = DepthNone,
        depth_format = Depth_u16,
        depth_only = false,
        filter: TextureFilter = Linear,
        tex_type: TextureType = Tex2D,
        depth_filter: TextureFilter = Linear,
        depth_tex_type: TextureType = Tex2D,
        layer_count = 1,
        texture: Texture = nil,
    ): Framebuffer
proc set_attachments(self: Framebuffer; layer, mipmap_level: int)
proc enable*(self: Framebuffer, rect = none((int32,int32,int32,int32)),
        layer = -1, mipmap_level = 0, mark_textures = true): Framebuffer {.discardable.}
proc clear*(self: Framebuffer, color = vec4(0,0,0,0), clear_color = true, clear_depth = true, layer = -1) {.inline.}
proc disable*(self: Framebuffer)
proc draw*(dest: Framebuffer, shader_mat: Material, inputs: seq[Texture], 
        rect = none((int32,int32,int32,int32)), layer = -1, mipmap_level = 0)
proc get_framebuffer_status_string*(self: Framebuffer): string
proc generate_mipmap*(self: Framebuffer, custom_shader: Material = nil)
proc destroy*(self: Framebuffer, remove_from_context: bool = true)
proc newMainFramebuffer*(engine: MyouEngine): Framebuffer
# End forward declarations

import std/strformat
import ../platform/gl
import ../objects/cubemap_probe
import ../postprocessing/effect_shaders
import ./render
import ./texture
import ./ubo


var active_buffer: Framebuffer
var active_rect: (int32,int32,int32,int32)
var active_layer: int

proc newFramebuffer*(engine: MyouEngine, 
        width, height: int,
        format: TextureFormat,
        depth_type: FramebufferDepthType = DepthNone,
        depth_format = Depth_u16,
        depth_only = false,
        filter: TextureFilter = Linear,
        tex_type: TextureType = Tex2D,
        depth_filter: TextureFilter = Linear,
        depth_tex_type: TextureType = Tex2D,
        layer_count = 1,
        texture: Texture = nil,
    ): Framebuffer =

    assert Tex3D notin [tex_type, depth_tex_type],
        "Tex3D framebuffer not supported"
    assert TexExternal notin [tex_type, depth_tex_type],
        "TexExternal framebuffer not supported"

    let self = new Framebuffer
    # TODO: detect support for float textures and framebuffers in renderer
    if width == 0 or height == 0:
        raise newException(ValueError, "Invalid framebuffer size")
    self.engine = engine
    self.width = width
    self.height = height
    self.layer_count = layer_count
    self.format = format
    self.depth_type = depth_type
    var tex_type = tex_type
    # self.filters_should_blend = false
    if not depth_only:
        if texture == nil:
            if self.texture != nil:
                # TODO: rely on destructor instead
                self.texture.destroy()
            self.texture = engine.newTexture("fb_tex", width, height,
                    layer_count, format, tex_type=tex_type, filter=filter)
            # TODO: set as loaded only after having rendered something?
            self.texture.loaded = true
            self.texture.setExtrapolation Clamp
            if self.texture.needsMipmap:
                self.texture.generateMipmap()
        else:
            # Use an existing texture
            # (to E.G. render to a mipmap of itself without depth buffer)
            self.texture = texture
            tex_type = texture.tex_type
    # TODO: fall back to other texture types when not supported
    if self.depth_texture != nil:
        self.depth_texture.destroy()
    self.depth_texture = nil
    if depth_type == DepthTexture:
        self.depth_texture = engine.newTexture("fb_depth", width, height,
                        layer_count, depth_format, tex_type=depth_tex_type,
                        filter=depth_filter)
        self.depth_texture.loaded = true
    var fb, rb: GLuint
    glGenFramebuffers(1, fb.addr)
    self.framebuffer = fb
    glBindFramebuffer(GL_FRAMEBUFFER, fb)
    self.set_attachments(0, 0)
    if depth_type == DepthRenderBuffer:
        glGenRenderbuffers(1, rb.addr)
        self.render_buffer = rb
        glBindRenderbuffer(GL_RENDERBUFFER, rb)
        glRenderbufferStorage(GL_RENDERBUFFER, depth_format.toInternalFormat, width.GLsizei, height.GLsizei)
        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, rb)
    self.is_complete = glCheckFramebufferStatus(GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE
    self.has_mipmap = false
    # self.last_viewport = nil
    if self.texture != nil:
        self.texture.unbind()
    if self.depth_texture != nil:
        self.depth_texture.unbind()
    if rb != 0:
        glBindRenderbuffer(GL_RENDERBUFFER, 0)
    glBindFramebuffer(GL_FRAMEBUFFER, 0)
    active_buffer = nil
    engine.all_framebuffers.add(self)
    return self

proc set_attachments(self: Framebuffer; layer, mipmap_level: int) =
    let attachments = [GL_COLOR_ATTACHMENT0, GL_DEPTH_ATTACHMENT]
    for i,tex in [self.texture, self.depth_texture]:
        if tex != nil:
            if tex.tex_type == Tex2DArray:
                assert layer >= 0, "Texture array layer must be specified"
                glFramebufferTextureLayer(GL_FRAMEBUFFER, attachments[i],
                    tex.storage.tex.GLuint, mipmap_level.GLint, layer.GLint)
            elif tex.tex_type == TexCube:
                assert layer >= 0, "Texture cube side must be specified"
                glFramebufferTexture2D(GL_FRAMEBUFFER, attachments[i],
                    (GL_TEXTURE_CUBE_MAP_POSITIVE_X.int + layer).GLenum,
                    tex.storage.tex.GLuint, mipmap_level.GLint)
            elif self.current_mipmap_level != mipmap_level:
                glFramebufferTexture2D(GL_FRAMEBUFFER, attachments[i], 
                    tex.storage.target, tex.storage.tex.GLuint, mipmap_level.GLint)

proc enable*(self: Framebuffer, rect = none((int32,int32,int32,int32)),
        layer = -1, mipmap_level = 0, mark_textures = true): Framebuffer {.discardable.} =
    self.has_mipmap = false
    var left, bottom, width, height = 0'i32
    if not rect.isSome:
        width = self.width.int32
        height = self.height.int32
    else:
        (left, bottom, width, height) = rect.get
    width = width shr mipmap_level
    height = height shr mipmap_level
    if active_buffer == self and active_rect == (left,bottom,width,height) and
            active_layer == layer and self.current_mipmap_level == mipmap_level:
        return
    self.current_width = width
    self.current_height = height
    if self.texture != nil:
        self.texture.unbind()
    if self.depth_texture != nil:
        self.depth_texture.unbind()
    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, self.framebuffer)
    when not defined(opengl_es):
        if self.use_sRGB:
            glEnable(GL_FRAMEBUFFER_SRGB)
    self.set_attachments(layer, mipmap_level)
    self.current_mipmap_level = mipmap_level
    active_layer = layer
    glViewport(left, bottom, width, height)
    active_rect = (left,bottom,width,height)
    if active_buffer != nil and active_buffer != self:
        if active_buffer.texture != nil:
            active_buffer.texture.is_framebuffer_active = false
        if active_buffer.depth_texture != nil:
            active_buffer.depth_texture.is_framebuffer_active = false
    active_buffer = self
    if mark_textures and self.texture != nil:
        self.texture.is_framebuffer_active = true
    if mark_textures and self.depth_texture != nil:
        self.depth_texture.is_framebuffer_active = true
    # filters_should_blend = self.filters_should_blend
    return self

proc clear*(self: Framebuffer, color = vec4(0,0,0,0), clear_color = true, clear_depth = true, layer = -1) {.inline.} =
    self.enable(layer=layer)
    var bits: uint32
    if clear_color:
        glClearColor(color.r, color.g, color.b, color.a)
        bits = GL_COLOR_BUFFER_BIT.uint32
    if clear_depth:
        bits = bits or GL_DEPTH_BUFFER_BIT.uint32
    glClear(bits.GLbitfield)

proc disable*(self: Framebuffer) =
    glBindFramebuffer(GL_FRAMEBUFFER, 0)
    when not defined(opengl_es):
        if self.use_sRGB:
            glDisable(GL_FRAMEBUFFER_SRGB)
    active_buffer = nil
    active_layer = -1
    if self.texture != nil:
        self.texture.is_framebuffer_active = false
    if self.depth_texture != nil:
        self.depth_texture.is_framebuffer_active = false

proc draw*(dest: Framebuffer, shader_mat: Material, inputs: seq[Texture], 
        rect = none((int32,int32,int32,int32)), layer = -1, mipmap_level = 0) =
    
    glUseProgram(0)
    dest.enable(rect, layer, mipmap_level, mark_textures=false)
    var i = 0
    for tex in shader_mat.textures.mvalues:
        if i >= inputs.len: break
        tex = inputs[i]
        inc(i)
    if shader_mat.ubos.len != 0:
        let ubo = shader_mat.ubos[0]
        if ubo.name == "EffectShaderInputs":
            var sto = ubo.storage(EffectShaderInput)
            var i = 0
            for tname,tex in shader_mat.textures:
                sto[i] = EffectShaderInput(
                    size: tex.vec3_size,
                    px_size: vec3(1)/sto[i].size,
                    px_lod: tex.mipmapHigh.float32,
                    lod: mipmap_level.float32,
                )
                inc(i)
            ubo.update()
                
    # TODO: use framebuffers as inputs and pass the last camera data used?
    # and the last depth buffer

    let renderer = dest.engine.renderer
    glDepthMask(false)
    glDepthFunc(GL_ALWAYS)
    let use_frustum_culling = renderer.use_frustum_culling
    renderer.use_frustum_culling = false
    var cd = RenderCameraData(world2cam: mat4(), cam2world: mat4(), projection_matrix: mat4())
    if layer != -1 and inputs.len != 0 and inputs[0].tex_type == TexCube:
        cd.world2cam = getCubemapSideMatrix(layer)
        cd.cam2world = transpose(cd.world2cam)
    renderer.draw_mesh(renderer.bg_mesh, mat4(), cd, -1, shader_mat)
    renderer.use_frustum_culling = use_frustum_culling
    glDepthFunc(GL_LEQUAL)
    glDepthMask(true)
    if shader_mat.ubos.len != 0:
        let ubo = shader_mat.ubos[0]
        if ubo.name == "EffectShaderInputs":
            ubo.unbind()

proc get_framebuffer_status_string*(self: Framebuffer): string =
    glBindFramebuffer(GL_FRAMEBUFFER, self.framebuffer)
    let status = glCheckFramebufferStatus(GL_FRAMEBUFFER)
    result = case status:
        of GL_FRAMEBUFFER_COMPLETE: "GL_FRAMEBUFFER_COMPLETE"
        of GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT: "GL_FRAMEBUFFER_INCOMPLETE_ATTACHMENT"
        of GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS: "GL_FRAMEBUFFER_INCOMPLETE_DIMENSIONS"
        of GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT: "GL_FRAMEBUFFER_INCOMPLETE_MISSING_ATTACHMENT"
        else:
            &"Unknown status {status.GLint}"
    self.disable()

# TODO: move to renderer or to engine
var cube_mipmap_shader: Material

proc generate_mipmap*(self: Framebuffer, custom_shader: Material = nil) =
    if self.texture.needsMipmap and not self.has_mipmap:
        if active_buffer == self:
            self.disable()
        
        var custom_shader = custom_shader
        if custom_shader == nil and self.texture.tex_type == TexCube:
            # cube mipmaps seem to be broken, use a custom shader for it
            if cube_mipmap_shader == nil:
                cube_mipmap_shader = self.engine.newEffectShader(@["cube"],
                    texture_types = @[TexCube],
                    code = "outColor = vec4(textureLod(cube, coord3D, 0.0).rgb, 1.0);",
                    add_input_size_ubo = false)
            custom_shader = cube_mipmap_shader

        if custom_shader == nil:
            # use OpenGL built-in method
            self.texture.bind_it()
            glGenerateMipmap(self.texture.storage.target)
            self.has_mipmap = true
            return

        let filter = self.texture.filter
        let mipmap_range = self.texture.mipmap_range
        let layer_range = if self.texture.tex_type == TexCube:
            0 ..< 6
        else:
            -1 .. -1
        self.texture.setFilter Linear
        for m in mipmap_range[0] .. mipmap_range[1] - 1:
            self.texture.setMipmapRange(m, m)
            for i in layer_range:
                self.draw(custom_shader, @[self.texture], 
                    layer = i, mipmap_level = m+1)
        self.texture.setFilter filter
        self.texture.setMipmapRange(mipmap_range[0], mipmap_range[1])
        self.has_mipmap = true

proc destroy*(self: Framebuffer, remove_from_context: bool = true) =
    if active_buffer == self:
        self.disable()
    if self.texture != nil:
        self.texture.destroy()
    if self.depth_texture != nil:
        self.depth_texture.destroy()
    if self.render_buffer != 0:
        glDeleteRenderbuffers(1, self.render_buffer.addr)
    glDeleteFramebuffers(1, self.framebuffer.addr)
    if remove_from_context:
        var index = self.engine.all_framebuffers.find(self)
        if index != -1:
            self.engine.all_framebuffers.del(index)

proc newMainFramebuffer*(engine: MyouEngine): Framebuffer =
    result = new Framebuffer
    result.engine = engine
    result.framebuffer = 0
    result.is_complete = true
    result.use_sRGB = not engine.use_glsl_tone_mapping